Prefabricated straw passive house in Denmark

BACHELOR PROJECT PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

Group 2- VIA HORSENS Autumn semester 2015

AUTHORS : Etienne Lesage 231343 AUTHORS Bernat Riera 232065 BERNAT RIERA (232065) Joao Santos 232070 ETIENNE LESAGE (231343) JOAO SANTOS SUPERVISOR SUPERVISOR Arnaldo Landivar ARNALDO LANDIVAR landivar.a@gmail.com VIA – HORSENS AUTUMN 2015

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INDEX I.

Project description .................................................................................................................................. 7 1. Introduction ............................................................................................................................. 7 2. Background of the members ................................................................................................... 7 3. Purpose.................................................................................................................................... 8 4. Problem Formulation .............................................................................................................. 8 5. Delimitations ........................................................................................................................... 9 6. Methods and models............................................................................................................... 9

II. Energy renovation in Denmark ............................................................................................................... 9 III. Climate data in Denmark ....................................................................................................................... 13 IV. What is a Passive House? ...................................................................................................................... 15 V. Danish Building Regulation.................................................................................................................... 17 VI. Comparison between Passive House Standard and B2020 ................................................................... 18 VII. Straw

18 7. Properties of the straw.......................................................................................................... 20

VIII. Architecture........................................................................................................................................... 25 8. Previous solutions ................................................................................................................. 26 9. Number of floors ................................................................................................................... 28 10. Wall thickness...................................................................................................................... 29 11. Wall configuration ............................................................................................................... 29 12. Ground floor ........................................................................................................................ 30 13. First floor ............................................................................................................................. 30 14. Stairs .................................................................................................................................... 31 15. Roof ..................................................................................................................................... 32 IX. Structure ................................................................................................................................................ 32 16. Dead loads ........................................................................................................................... 32 17. Live loads ............................................................................................................................. 34 18. Snow loads .......................................................................................................................... 35 X. Seismic Design ....................................................................................................................................... 35 19. Basic design principles......................................................................................................... 35 20. Strength and torsional rigidity............................................................................................. 35 21. Adequate foundation .......................................................................................................... 36 22. Structural Regularity............................................................................................................ 36 23. MODAL ANALYSIS (simplified method) ............................................................................... 38 PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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24. Safety factors regarding the loads ...................................................................................... 39 XI. LOAD COMBINATIONS ........................................................................................................................... 40 XII. WIND CALCULATION ............................................................................................................................. 40 25. BASIC WIND VELOCITY ........................................................................................................ 40 26. AERODYNAMIC RUGOSITY OF THE TERRAIN ....................................................................... 40 27. WIND VELOCITY AND DYNAMIC PRESSURE ........................................................................ 42 28. INTERNAL WIND LOADS ...................................................................................................... 46 29. Straw in the walls – structural? ........................................................................................... 47 30. Beams over doors and windows ......................................................................................... 48 31. Roof ..................................................................................................................................... 48 XIII. Fire

49

XIV. Panel design .......................................................................................................................................... 51 XV. Other possible insulation materials ...................................................................................................... 53 32. Cork ..................................................................................................................................... 53 33. Sheep wool .......................................................................................................................... 54 34. Wood fiber board ................................................................................................................ 55 35. Recycled loose cellulose (Warmcel) .................................................................................... 56 36. Exterior Impermeable layer................................................................................................. 58 37. Gutex Multiplex-top ............................................................................................................ 59 38. OSB panels ........................................................................................................................... 60 39. Plasters ................................................................................................................................ 61 40. Comparison between the insulation materials ................................................................... 65 41. Membranes and plastic materials ....................................................................................... 66 42. Airtight membrane .............................................................................................................. 67 XVI. Final chosen materials for the interior and exterior faces of the panel ............................................... 68 XVII.

Final chosen materials for roof ............................................................................................... 71

XVIII.

Final chosen materials for the ground slab............................................................................. 74

XIX. Windows in a passive house: ................................................................................................................ 77 43. Frames ................................................................................................................................. 77 44. Glazing ................................................................................................................................. 80 XX. Main door .............................................................................................................................................. 82 XXI. Foundations ........................................................................................................................................... 83 XXII.

Details ..................................................................................................................................... 85 45. Panel-panel south................................................................................................................ 86

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46. Panel-panel no south .......................................................................................................... 88 47. Roof south ........................................................................................................................... 90 48. Roof slab ending in east or west façade.............................................................................. 92 49. Foundation-wall south and north ....................................................................................... 93 50. Wall-foundation east and west façades .............................................................................. 95 51. Window detail ..................................................................................................................... 97 XXIII.

Energy part .............................................................................................................................. 99 52. Different systems to heat the house ................................................................................... 99 53. Different sustainable ways to provide air heating ............................................................ 105 54. Dimensioning the earth tube ............................................................................................ 114 55. What if the house has to respect the building regulation 2015 and 2020?...................... 124

XXIV.

What if the client wants to be off-grid? ................................................................................ 132 56. Dimensioning the stove to deliver heat and DHW during winter ..................................... 134 57. Dimensioning the thermal solar panels for DHW in summer time. .................................. 135 58. Dimensioning photovoltaic panels .................................................................................... 136 59. Rainwater harvesting system ............................................................................................ 141

XXV.

Velux Daylight Visualizer ....................................................................................................... 142

XXVI.

Conclusions ........................................................................................................................... 145

XXVII.

Annexes ................................................................................................................................. 146 60. Structural Calculations ...................................................................................................... 146 61. 1st floor slab beams calculation ......................................................................................... 146 62. Stair Calculation................................................................................................................. 148 63. Middle Step - calculation ................................................................................................... 155 64. Beam.................................................................................................................................. 162 65. Load in the steel bars ........................................................................................................ 163 66. Column Calculation – first try ............................................................................................ 165 67. Column calculation – second try ....................................................................................... 167 68. Interview ........................................................................................................................... 169

XXVIII.

Bibliography and webgraphy ................................................................................................ 169

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Figure 1 : RETScreen 4, Billund Climate1 RETScreen 4, Billund Climate ..........................................................14 Figure 2 : RETScreen 4, Aalborg Climate ..........................................................................................................14 Figure 3: RETScreen 4, Copenhagen Climate ...................................................................................................15 Figure 4 Passive house criteria (Passive House Institute, s.f.)..........................................................................16 Figure 5 Wheat straw (Google, s.f.)..................................................................................................................19 Figure 6 Oat (Google, s.f.).................................................................................................................................19 Figure 7 Comparison of thermal conductivity values (Passipedia, s.f.)............................................................20 Figure 8 Sound level examples in dB ................................................................................................................24 Figure 9 3D explosion view of the panel and 3D view of the panel .................................................................52 Figure 10 Cork boards (Amorim Isolamentos (Company), s.f.) (Cork Link (Company), s.f.).............................54 Figure 11 Sheep wool as insulator (EcoMerchant, s.f.) ...................................................................................54 Figure 12 Wood fiber (Gutex , s.f.) ...................................................................................................................55 Figure 13Warmcel insulation (Warmcel, s.f.) ...................................................................................................57 Figure 14 Gutex Multiplex-top (Gutex, s.f.)......................................................................................................59 Figure 15 OSB Panel .........................................................................................................................................60 Figure 16 COB once plastered (Argilus, s.f.) .....................................................................................................62 Figure 17 Materials of the wall (U-Wert, s.f.)...................................................................................................68 Figure 18 Wall characteristics (U-Wert, s.f.) ....................................................................................................69 Figure 19 Relative humidity in the wall (U-Wert, s.f.) ......................................................................................70 Figure 20 Temperature changes during the day (U-Wert, s.f.) ........................................................................70 Figure 21 temperature variability between outside and inside (U-Wert, s.f.) .................................................71 Figure 22 Example roof for the building (Google, s.f.) .....................................................................................71 Figure 23 Example roof for the building (Google, s.f.) .....................................................................................72 Figure 24 Materials detail of roof slab (U-Wert, s.f.) .......................................................................................72 Figure 25 Characteristics of the roof slab (U-Wert, s.f.) ..................................................................................72 Figure 26 materials in the roof detail (U-Wert, s.f.) .........................................................................................73 Figure 27 temperature variances during the day (U-Wert, s.f.) .......................................................................73 Figure 28 temperature changes in interior and exterior of the house (U-Wert, s.f.) ......................................74 Figure 29 materials for the ground slab (U-Wert, s.f.) .....................................................................................75 Figure 30 characteristics for the ground slab (U-Wert, s.f.) .............................................................................75 Figure 31 relative humidity in the ground floor (U-Wert, s.f.) .........................................................................75 Figure 32 temperatures variability in ground slab (without mussel shells) (U-Wert, s.f.) ...............................76 Figure 33 temperature variation during the day (U-Wert, s.f.)........................................................................76

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Figure 34 Thermal development Biobased Cassette (Passive House Institute, s.f.)

Figure 35 Biobased Cassette (Tifabos, s.f.) ......................................................................................................................................78 Figure 36 Thermal development (Passive House Institute, s.f.)

Passivhausfenster (Fenster Buck, s.f.)

Figure

37

VĂ–RDE-

79

Figure 38 Thermal data (Passive House Institute, s.f.) .....................................................................................80 Figure 39 Thermal development (Passive House Institute, s.f.)

Figure 40 Progression (SLAVONA, s.f.) .....80

Figure 41 Iplus Advanced 1.0T thermal data (Passive House Institute, s.f.) ....................................................81 Figure 42 ClimaGuard Premium2 (Passive House Institute, s.f.) ......................................................................81 Figure 43 SGG Planitherm Ultra N (Passive House Institute, s.f.) ....................................................................81 Figure 44 Picture of the door (New Rock, s.f.)

Figure 45 Section door Figure 46 Section door with glass 83

Figure 47 Panel-panel detail in the building.....................................................................................................86 Figure 48 Panel-panel heat flux ........................................................................................................................87 Figure 49 Panel-panel temperatures variation ................................................................................................87 Figure 50 Panel-panel detail .............................................................................................................................88 Figure 51 Panel-panel temperature variations ................................................................................................89 Figure 52 Panel-panel heat flux ........................................................................................................................89 Figure 53 South roof detail ...............................................................................................................................90 Figure 54 Temperature flux between the materials ........................................................................................91 Figure 55 Heat flux in the roof .........................................................................................................................91 Figure 56 Roof detail with AutoCAD.................................................................................................................92 Figure 57 Temperatures in the roof .................................................................................................................92 Figure 58 Therm heat flux ................................................................................................................................93 Figure 59 Foundation AutoCAD detail ..............................................................................................................94 Figure 60 Temperature flux from Therm .........................................................................................................94 Figure 61 Heat flux from Therm .......................................................................................................................95 Figure 62 Foundation AutoCAD detail ..............................................................................................................95 Figure 63 temperature through the materials .................................................................................................96 Figure 64 analyzation heat flux ........................................................................................................................96 Figure 65 Window detail in AutoCAD ...............................................................................................................97 Figure 66 Temperatures in the materials .........................................................................................................98 Figure 67 Heat flux ...........................................................................................................................................98 Figure 68: Radiator (thermaskirt, s.d.) .............................................................................................................99 Figure 69: Manifold installation for pipes going to the radiators (media.xpair, s.d.) ....................................100 Figure 70: Section of a wood floor heating system (williambeardflooring, s.d.) ...........................................101 PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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Figure 71: Wall heating system showing the layout of the pipes in the wall (spec-net., s.d.) .......................102 Figure 72: Ventilation system of the house showing the heat exchanger and the heat device (Passipedia, s.d.) ........................................................................................................................................................................103 Figure 73: Rocket mass heater with wood. Picture from Friland trip in Jens Peter Mølgaard House......104 Figure 74 Rocket mass heater section showing the principle of heating hanks to the smoke ......................104 Figure 75: Compact unit scheme, composed of a heat recovery system, a small heat pump on the exhaust air heating the boiler that we can use the water from to heat up the supply air to the temperature needed (http://passiv.de, s.d.) ....................................................................................................................................106 Figure 76: Compact unit composed of a small heat pump, the heat recovery system and the water tanks below. (nilan.dk, s.d.) .....................................................................................................................................107 Figure 77: Compact unit in Passive heat recovery mode, only the air heat exchanger is working (nilan.dk, s.d.) ........................................................................................................................................................................108 Figure 78: Compact unit in Active heat recovery mode, the heat pump is used to heat up the water tank and maybe also to heat up the air to temperature depending on the outside temperature. (nilan.dk, s.d.) ......108 Figure 79: Compact unit in bypass mode, the fresh air goes directly to the house and the exhaust air goes directly outside without using the air counter flow heat exchanger (nilan.dk, s.d.) .....................................109 Figure 80: Compact unit in hot water mode, the heat pump is used to deliver heat to the water tank to heat up the water for domestic hot water usage...................................................................................................109 Figure 81: Compact unit in Active cooling mode, the "hot" fresh air is cooled and goes directly to the house and the exhaust air is heated up and then throw outside. ............................................................................110 Figure 82: Water heating element, taking the heat from the hot water tank to heat to the desired temperature the air before being supply to the rooms. (Nilan dk, s.d.) .............................................................................111 Figure 83: "Wind towers" in Iran allowing to catch the hot dry wind cool it with water and so have a confortable indoor temperature during hot days. (FIabitat, s.d.)..................................................................115 Figure 84: Iran wind towers technical principle. ............................................................................................116 Figure 85: Inlet air extractor of an earth tube system (FIabitat, s.d.) ............................................................118 Figure 86: Earth tube made of PEHD ringed on the outside surface (FIabitat, s.d.) ......................................118 Figure 87: Principal of earth tube system showing the secondary pipe and the trap for the condensate water (FIabitat, s.d.)..................................................................................................................................................119 Figure 88: "Jupiter" tool linked to google earth in order to get borehole profile. Here is a screenshot on VIA campus location in Horsens. At the top of the picture you can notice the different borehole. ....................120 Figure 89: Borehole profile in Energy Pack in VIA campus location, where we can notice that between 0.5 and 5 m depht the soil is composed of sand. (See the complete sheet in the annexe D) ....................................120 Figure 90: Screenshot of GAEA software about the soil properties, choosing "Sand" the software directly give us the Density, Heat capacity, and Thermal conductivity. .............................................................................121 Figure 91: Drawing showing the earth tube system around the house and the other components. ...........123 Figure 92: Part of certified data sheet of the WS 320 KET, showing that the electric heater for pre-heating the air will start when the temperature outside is less than -6.3°C.....................................................................126 Figure 93: Danfoss data sheet about an air to water heat pump. .................................................................127 PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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Figure 94 : Layout of an off-grid solar panels connections between the components (waldenlabs, s.d.) ....137 Figure 95 Daylight factor for the ground floor ...............................................................................................142 Figure 96 illuminance during December in the ground floor (worst case) ....................................................143 Figure 97 illuminance during June in the ground floor (best case) ................................................................143 Figure 98 Daylight factor for the first floor ....................................................................................................144 Figure 99 illuminance during December in the first floor (worst case) .........................................................144 Figure 100 illuminance during June in the first floor (best case) ...................................................................145

I. Project description Introduction The project is about the design of a passive single family house made of a prefabricated panels with a timber structure and straw as a main insulation. Timber and straw has been used as a building material for thousands of years not only because of its availability but for its properties as well. So, the main idea to combine straw and timber, which makes a good environmentally friendly, cheap and energy efficient combination. Another aim of this project is to try to avoid all kind of materials with chemicals in them and with huge CO2 emissions during the manufacturing.

Background of the members Joao Santos Studied Civil Engineering for 4 semesters on Polytechnic Institute of Leiria (Portugal) and now he is a credit transfer student doing his 6th and 7th semester in VIA University. At VIA University he has/had the following subjects: Basic Timber Structures, Timber Structures, Assembling Precast Concrete Structures, Energy Renovation, Sustainable Buildings, Project / Construction Planning Management, Building services, Masonry Structures and Passive Houses.

Bernat Riera He had been studying Building Engineering (not finished) at University of Catalonia, Spain. He has studied 3 years in UPC. He has done subjects related on construction, installations, materials, structures and others.

In VIA University College he is studying Energy Design specialization, attending subjects as Sustainable Buildings, Shallow Geothermal Energy, Passive Houses, Sustainable Energies, Indoor Environment, Ventilation systems and Thermodynamics. He has been working for 4 months in a passive house company called Farhaus in Spain.

Etienne Lesage He studies civil-engineering in 7th semester (sustainable city planning, thermodynamics, shallow geothermal system and indoor environment) he did the 6th one last semester he had as lectures: Passive house, sustainable energy, sustainable building, smart grid, energy renovation. Autumn semester in 2014 he

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completed the 4th semester of Architecture and Construction Management in VIAUC Horsens. He learnt the basics of Revit. He did an elective self-subject dealing with solar trackers.

He completed a two years diploma of civil engineering (DUT) in the IUT genie-civil (sept 2012- June 2014), UniversitĂŠ de Picardie Jules Verne, Amiens, France. He developed his skills in Autocad 2D, Microsoft project, static analyse (Concrete, steel, wood), planning and management on a building site.

He did 10 weeks of internship during the summer 2013 in Paris. The site was about to renovate tower social houses (re-insulation of the facades and improvements in each dwellings), with the tenants still occupying their dwelling.

His aim in this project is to be able to make choices in order to get the better energy efficiency and a cost effective building in order to have a passive - sustainable single family house.

Purpose Nowadays the way to build is different from many years ago as the aim now is to have energy efficiency building avoiding waste of energy and reduce its consumption at the same time. It is known by all that the household is the biggest consumer of energy. Looking at Denmark climate it is obvious that the building insulation has to be made in a proper way. The choice of straw as insulation might reduce the CO2 foot-print of the house.

One way to be sure that the building will not consume so much energy is to have a certification to prove it, some of them are really used in the world such as LEED, BREEAM, HQE and Passive House certification. The last one that is going to be taken into consideration to build our single family house located in Denmark.

Finally, the purpose of the project is to be able to get the passive house certification using prefabricated elements that can be assembled in an easy way knowing some basics (by workers or owners of the house) and that is modular, which means that each blocks have the same way to be build and can be assemble as much as it is needed. These prefabricated elements will be fill in with straw which is going to act as the insulation of the house. Also the purpose constructing this single family house is to have the less grey energy consumptions of the materials used. An option could be if it is necessary (depending on the location of the house) to use renewable energies to supply the house in energy.

Problem Formulation Basis 1) Why the choice of straw as insulation? And wood as structural material?

Architecture/structure 2) Which are the architectural options to make the house more efficient and at the same time give the building a modern look, taking in account the surroundings?

3) What are the structural solutions for the prefabricated elements to make the whole structure fulfil the Danish standards?

4) Which will be the way to assemble these prefabricated elements?

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6) How is going to fit the modular prefabricated elements with straw inside as insulation?

7) Is it possible to reach the passive house certification using prefabricated elements?

8) How much the energy consumption the family house will have?

9) What are the materials we should use to reduce as much as possible the grey energy of the house? Which alternatives in using materials that are more environmental friendly?

10) Is this method can be used in other countries in Europe? What should be changed?

Delimitations In that project because of lack of time and knowledge some aspects will not be regarded: - Geotechnical calculation - Acoustic calculations - Pipe calculations for water (pressure) - Connections with the sewer system, fresh water supply, heating water supply of the municipality.

- Details drawing might not be as accurate as it should be, because of the lack of knowledges in Revit drawing and AutoCAD drawing.

- Connectors between panels (iron nails or others) - Final budget due to the difficulties to find a real prices and do not make a wrong estimation.

Methods and models Software’s: -Revit -AutoCAD -PHPP Excel sheet -GAEA (earth tube dimensioning) -Robot structural design -Velux Daylight Visualizer -Microsoft project -Therm (start using because of the project) - U-wert (online program) - http://re.jrc.ec.europa.eu/ (online program for PV panels production) As it already exits some houses in Denmark which are made of straw it has been made an interview the owner of the house such as in the Friland community in the small village of Feldballe in Denmark.

II. Energy renovation in Denmark First of all, the focus of this project is reduce the energy consumption of a house in Denmark using the Passive House Standard in order to achieve a low energy consumption values. But, why? Why is the energy consumption of a dwelling so important?

In Denmark the energy sources have been changing during the last years, the renewable sources had been increasing, that means that the CO2 emissions are also decreasing because the fuel is not being used anymore. The consumption of coal and natural gas had decreased 17% and 14% respectively and the PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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renewable energy has increased 1.5%. In 2014, for example, Denmark had the lowest energy consumption for the last 30 years.

That means, Denmark is an example for many other countries, is trying to supply the country as much as possible with green energies, reducing the GDP consumption and try to establish a country working only with green energies in a future not far away from now.

Graphic. 1. Evolution of the energy consumed origin [Annex1]

Graphic 1 shows the evolution of the resources of the energies in Denmark, as it shows, is increasing fast, nowadays (2015) is known that the electricity needed in Denmark it can be fulfilled with the wind energy during the huge windy days. In addition, the Natural gas is also winning terrain to the Coal and Oil, and it is also good, because is less contaminant than them. However, the government in Denmark is also changing the building regulations often, trying to build more energy efficiently, as it can be seen in the new building regulations for 2015 and 2020. For example: Building Regulation 1995 a new 150 m2 house: 105 kWh/m2 per year.

The energy requirement 2006 a new 150 m2 house; 85 kWh/m2 per year.

Building Regulation 2010 a new 150 m2 house; 63.5 kWh/m2 per year.

Energy class 2015: a new 150 m2 house must use less than 37 kWh/m2 per year.

Energy class 2020: a new 150 m2 house must use less than 20 kWh/m2 per year.

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Graphic. 2 Energy requirements from different sectors [1]

The total energy consumption for the houses in order to compare it with other sectors, is around 30% of the total in Denmark, it is a huge part of the total consumed energy, that’s why it has to be improved in order to achieve less energy demand, which means less contamination and more green energy sources.

Graphic. 3Origin of the energy for the households [Annex 2]

As it is seen in the graphic 3, the number of houses that are consuming Oil and Coal had been decreasing and at the same time the renewable energies are increasing also the district heating.

Graphic. 4 Energy evolution from 1980 for the houses [Annex 2]

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The graphic number 4 shows how the household energy used had decreased during the last 30 years, it means, the new building insulation is getting better, as it does the renovation of the old ones and the efficiency of the heating systems. Between 1990 and 2010, the energy efficiency of households improved by 21%, the space heating improvement in efficiency was 21% as well. Substitution of old oil burners with new natural gas burners and district heating has contributed significantly to the improvement.

Graphic. 5 Electricity consumption per dwelling [Annex 1]

Here in the graph number 5, it can be seen the consumption for every house in Denmark, the last year was 2008, it is long time ago from now (2015). The average of the electricity consumption is the same in whole years roughly. If Denmark is compared with other European countries it can be seen:

Graphic. 6 Comparison energy consumption between countries [Annex 3]

Denmark has a lower electricity consumption than other countries because the number of inhabitants. If we do the calculation energy/person per year the results are: Denmark: 5,659,715



Germany: 82,588,548

1680 KWh/person

France: 64,942,871

2380 KWh/person

1670 KWh/person

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Italy: 61,142,221 

1130 KWh/person

UK: 63,489,234

1930 KWh/person

Population in those countries from nevertheless, if the percentage of energy consumed it is calculated, from 2005 to 2009 it can be seen: Denmark: -9.57% Germany: -3.33% France: +6.81% Italy: +2.9% UK: -2.51% The conclusion would be that Denmark is designing better buildings with improved insolation and solutions in order to reduce the energy consumption. Is the country which is growing faster improving the systems to reduce the consumption? Denmark’s indicative target is energy consumption of 744.4 PJ (17.781 Mtoe) in 2020. This involves a 12.6 % reduction in primary energy consumption compared with 2006.

III. Climate data in Denmark Denmark has a temperate climate, characterized by mild winters, with mean temperatures in January of 1.5 °C, and cool summers, with a mean temperature in August of 17.2 °C. Denmark has an average of 179 days per year with precipitation, on average receiving a total of 765 millimeters per year; autumn is the wettest season and spring the driest. The position between a continent and an ocean means that weather often changes.

Because of Denmark's northern location, there are large seasonal variations in daylight. There are short days during the winter with sunrise coming around 8:45 am and sunset 3:45 pm, as well as long summer days with sunrise at 4:30 am and sunset at 10 pm.

Below are shown the climate data from different places in Denmark from RETScreen 4 software. The overall conclusion is that the climate is almost the same around the country, in terms of temperatures, humidity rates, heights and degree days for heating and cooling.

The lowest temperature to take into account for the calculations in order to dimension all the insulation and materials for the walls is -12ºC.

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Figure 1 : RETScreen 4, Billund Climate1 RETScreen 4, Billund Climate

Figure 2 : RETScreen 4, Aalborg Climate

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Figure 3: RETScreen 4, Copenhagen Climate

IV. What is a Passive House?

The Passive House standard offers a cost-efficient way of minimizing the energy demand of new buildings in accordance with the global principle of sustainability, while at the same time improving the comfort experienced by building occupants. Also, helps on the sustainable energy sources for the energy demand.

The Passive House philosophy is following two basic principles that a: Principle 1: Optimize what is essential What makes the cost-efficient approach is that, optimizing those components of a building which are necessary in any case: The building envelope, the windows and the automatic ventilation system expedient anyway for hygienic reasons. Improving the efficiency of these components as the leak of heat from inside is reduced the savings achieved largely finance the extra costs of improvement.

Principle 2: Minimize losses before maximizing gains Passive Houses prevent available heat from escaping as rigorously as possible. And that reduces the extra energy consumption.

To fulfil the passive house standard it has to be followed the next requirements introducing all the data in PHPP program: PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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1. The Space Heating Energy Demand is not to exceed 15 kWh/m2 of net living space (treated floor area) per year or 10 W/m2 peak demand.

2. The Primary Energy Demand, is the energy to be used for the domestic applications (heating, hot water and domestic electricity) must not exceed 120 kWh/m2 of treated floor area per year.

3. In terms of Airtightness, a maximum of 0.6 air changes per hour at 50 Pascal pressure (ACH50), as verified with an onsite pressure test (in both pressurized and depressurized states).

4. Thermal comfort must be met for all living areas during winter as well as in summer, in order to avoid the overheating, no more than 10 % of the hours in a given year over 25 °C. 5. In order to achieve the passive house standard, the software PHPP is going to be used.

All of the above criteria are achieved through intelligent design and implementation of the 5 Passive House principles: thermal bridge free design, superior windows, and ventilation with heat recovery, quality insulation and airtight construction.

Figure 4 Passive house criteria (Passive House Institute, s.f.)

To apply all this criteria it is needed to do it through the following parameters: 

Thermal insulation

All the components of the exterior envelope of the house must be very well-insulated. For most cooltemperate climates, this means a heat transfer coefficient (U-value) of 0.15 W/ (m²K) as a maximum. In Denmark the recommended U-value of 0.1 W/(m²K) and the aim of the project is to fulfill the Danish requirements, it is going to be considered a value as close as possible to 0,1 W/(m²K) for the walls, ground slab and roof.

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Passive House windows

The window frames must be well insulated and fitted with triple low-e glazing filled with argon or krypton to prevent heat transfer. For most cool-temperate climates, this means a U-value of 0.80 W/ (m²K) or less for the whole window, with g-values around 50% (g-value= total solar transmittance, proportion of the solar energy available for the room). 

Ventilation heat recovery

Efficient heat recovery ventilation is good for indoor air quality and saving energy. In Passive House, the heat recovery system transfers at least 75% of the heat from the exhaust to the fresh air. 

Airtightness of the building

Uncontrolled leakage through gaps in the walls or windows must be smaller than 0.6 times/h of the total house volume per hour during a pressure test at 50 Pascal (both pressurized and depressurized). 

Absence of thermal bridges

In a Passive House there is no chance to have any thermal bridge, and if there is one it has to be minimized as much as possible. That concerns on the difficulties in order to build a dwelling with the passive house standard. ●

The passive house standard is essential in order to fulfil the 2020 rules regarding the reduction of Greenhouse Gas Emissions by 20% and increase the energy efficiency by 20%.

V.

Danish Building Regulation

The Danish Building Regulation established a conditions in order to regulate the energy consumption on the buildings or dwellings, nowadays the Building Regulation that it has to be followed in Denmark is the LEB2015, but as the energy consumption demands are decreasing in B2020, is going to be studied the B2020, is more restrictive.

Table. 1 Comparison between BR10, LEB 2015 and B2020 regarding primary energy consumption (including renewables)

Table. 2 Comparison between BR10, LEB 2015 and B2020 regarding primary energy consumption (without renewables)

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The Buildings class 2020 is achieved when the total demand for energy supply for heating, ventilation, cooling and domestic hot water per m² of heated floor area does not exceed 20 kWh/m²/year.

Class 2020 buildings shouldn’t be designed with a transmission loss more than 3.7 W per m² of the building envelope in the case of single storey buildings, 4.7 W for two-storey buildings and 5.7 W for buildings with three storeys or more.

Air changes regarding the airtightness of the envelope in class 2020 buildings can’t exceed 0.5 l/s/m² (if the height is 3 meters is going to be changing 0.54 times total volume/h as maximum) of the heated floor area when tested at a pressure of 50 Pa (determinate with the blower door test).

In class 2020 buildings there are also energy requirements for the roof, windows, doors, gates, hatches and skylight domes. There are also tighter requirements to the indoor climate in relation to daylight access, summer comfort and air quality.

In 2020 the U value for windows must not exceed 1.20 W/m²K, the external doors and hatches must not have a U value exceeding 0.80 W/m²K. Gates must have a maximum U value of 1.40 W/m²K. External doors with glazing must not have a U value exceeding 1.00 W/m²K or an energy gain through the door during the heating season of less than 0 kWh/m² per year.

VI. Comparison between Passive House Standard and B2020 DATA

PASSIVE HOUSE STANDARD

B2020

ENERGY DEMANDS (WITH HEAT PUMP)

15 kWh/m²/year

17.9 kWh/m²/year

ENERGY DEMANDS (DISTRICT HEATING)

15 kWh/m²/year

15.7 kWh/m²/year

AIR CHANGES (AIRTIGHTNESS)

0.6 times total volume/hour

0.54 times total volume/hour

VENTILATION HEAT RECOVERY EFFICIENCY

75%*

85%

DOOR U-VALUE

0.8 W/m²K

0.8 W/m²K

WINDOWS U-VALUE

0.8 W/m²K

1.2 W/m²K

Table. 3 Comparison with main values for energy between Passive House and B2020 (blue data is the most restrictive I each case ([Annex 8]) * 1 Some machines are up to 95% but is not a real efficiency, is not known if the efficiency of B2020 is up to 85% or not, otherwise, is a huge value non existing yet.

VII. Straw Straw: “a single stalk or stem, especially of a cereal grass.”

Taking in account the definition of straw, the aim of the project is to build a passive house with straw as a main insulation. But, straw is a general word, there are many kinds of straw, straw from rice, wheat, oats and rye as a principal kinds around the world. As far as it is known, the straw it’s the material remaining after the seed crop has been harvested.

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In Denmark the main production of straw is coming from wheat and also oats.

Figure 5 Wheat straw (Google, s.f.)

Figure 6 Oat (Google, s.f.)

Straw production in Denmark: As it can be seen in the graph 7, the not used straw can be counted by around 2 millions of tons every year in Denmark which can be used due to insulate buildings (2008 the most recent year with statistics). However, Denmark nowadays is also using the not used straw to get heat from it in for the district heating.

Graphic. 7 Annual straw production for usage, annual straw production by crops [Annex 4]

The aim to use straw is to use a natural material, which it can be found in almost everywhere around the world and it is not used at all for the producers because it doesn’t have many applications after the crop has been harvested. Using straw the use of chemical insulators and the petroleum derivatives are being avoided.

In 2020 it is predicted that Denmark will produce around 3 million tons of dry straw.

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Graphic. 8 Dry straw potential production for 2020

The difference of tons between the graph 7 and graph 8 is because the graph 7 is not showing the “dry matter”, it shows straw without saying anything about humidity and also the graph 8 shows a possible future on straw production for the countries, and graph 7 shows the current production of straw in Denmark.

Properties of the straw The main properties of the wheat straw to take in account during the construction of the house are:

Figure 7 Comparison of thermal conductivity values (Passipedia, s.f.)

“A straw-bale wall of 50 cm or more would be suitable for the Passive House.” (www.passipedia.org) ●

Thermal conductivity λ = 0.055 W/mK. (It is chosen the value from passipedia.org). But, the thermal conductivity of the straw depends on the way that you put it in the wall and the compression of the straw. Depending on the direction of the fibers and the density, the straw will have one value or another. The best value is 0.055 W/mK and it can be achieved with a density of 110 kg/m3 to 150

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kg/m3 putting them in horizontal way and the thicker face pointing to the wall, which makes the narrow face point to the ground and roof. The in the worst case, the straw within an specific compression and direction, is going to be considered 0.08 W/mK, a worse value in order to do not calculate with the best values and obtain a more realistic ones. ●

The vertical setting of the bales meant straw stalks were vertical to the heat flow direction increases the insulation properties.

●

About the fire resistance, a house built with bales has up to three times the fire resistance of a conventionally framed house. The main resistance is given from the plaster inserted after the straw insulation, without this plaster or other material covering the straw, the fire resistance would be much lower. The straw once it is packed and compressed becomes too dense and don’t allows enough air for the combustion. By analogy, it is easy to burn a piece of paper but a book takes more time to burn.

The fire results give as a low damage to the straw regarding to the fire, but a huge damage in order to the water needed to extinguish the fire.

The ASTM E-119 fire resistance test for plastered straw-bale wall passed for a 2 hour fire-wall assembly. The test consist in use a gas flame on one side of the wall was burning at approximately 1100 degrees Celsius while the temperature of the other side of the wall is continuously measured and on the other side of the wall the maximum temperature was 33.3 degrees Celsius. [Annex 6]

●

Structural properties, straw is not the best material due to be structural, it is tasted that after few days is compressing and changing the high of the building. During the project is not going to be used as a structural material but it does will help the wood to support the loads, but not as main part. Is not going to be considered during the calculations.

Graphic. 9 Straw carrying loads (Walker, s.f.)

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Table. 4 Examples of compressed straw (Walker, s.f.)

As it is shown in the graph 9 and table 1, if the straw would be structural it would reduce the height of the wall due to the deflection, as the straw is compressible. ●

The density of the straw as it can be compressed is changing depending on the compression. It is practical for further use to use bales with high density (110 to 150 kg/m3) because these offer multiple advantages such as better insulation and mechanical properties, improved heat insulation capacity and sound insulation. In our project is going to be considered the highest density: 150 kg/m3 in order to calculate the total loads with a safety numbers.

●

The live inside the straw bales, when microbial activity starts is mainly with the death of a plant – in the case of straw.

The decomposition of the straw in the soil or in the walls is changing because few different reasons: - Presence of moisture, which highly increase the amount of bacteria. In the wall theoretically there is no water, but in the soil.

- The dry and dark environment in the wall eliminates itself the amount of living bacteria, because they need moisture but also light.

- The number of nutrients from the wall is low comparing to the soil.

In conclusion, the decomposition of the straw because the bacteria is not going to be a problem if the right construction process is well done, because the low presence of moisture, the no light to the straw and the not contact between the soil and the straw.

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Graphic. 10 Straw general characteristics (Wihan, s.f.)



Is recommend to use only bales with moisture content below 20% (dry-weight basis below 20%), but after to consult the issue with some experts they considered 15% of humidity is the maximum value that should be used in wall construction. Otherwise, as it is seen, the percentage of straw decomposition per day it is really high. (see graphic 10).

●

The straw bale walls would be excellent candidates for use an inexpensive outdoor barriers to reduce environmental noises such as highway noise. The T for bale wall was 59.8 dB for 50.8 cm wall, it

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means if a discotheque it is placed outside (110 dB) inside is going to be 50 dB more or less, and that means the sound inside the house is going to reach the levels of an urban surrounding. (see figure 8)

Figure 8 Sound level examples in dB

●

Fungicides are not used because of the chemical contents and another reason could be the belief that good design, well executed details, faultless plaster (or wall cover) and regular maintenance are sufficient to keep the straw bales in perfect condition.

●

Price: based on a selling price of straw of 413 DKK/ton straw (55.4 EUR) find that increased mobilization of straw generates positive income for the farmer in the order of 159 DKK/ton straw (21.3 EUR). With a density of 110 kg/m3 means 1000/110 ≈ 9 m3 in a wall of 0,5m thick means around 18 m2 of wall cost 159 DKK directly from the farmer.

●

Calculating the approximate overall CO2 emissions of 1kg of baled local straw: Embodied energy of baled straw = 0.24 MJ/kg.



On average, 1 MJ of embodied energy produces 0.098 kg of CO2. This means that 1 kg of baled straw with embodied energy 0.24 MJ/kg produces 0.24 ∗ 0.098 = 0.023 kg of CO2. Straw has up to 60% of carbon by weight. It means that 1 kg of straw contains 0.6 kg of carbon.

1 kg of carbon in the presence of oxygen forms approximately 3.7 kg of CO2. There is about 0.6 ∗ 3.7 = 2.22 kg of stored CO2 in 1 kg of straw.

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Kg CO2 (embodied energy) − kg CO2 (stored) 1 kg baled straw = kg total CO2 emissions 1 kg baled straw 0.023 - 2.22 = - 2.197 kg/kg. (See graph 11)

Graph. 1 CO2 emissions by weight released by production of 1 kg of material (Wihan, s.f.)

CO2 emissions, the only emissions of the straw is when it is recollected and during the transportation.

A truck travels 2-3 km on one liter of diesel oil, thereby emitting 2.7 kg CO2. Therefore, the CO2 emission can be estimated at approx. 1 kg per km travelled.

As far as we know that it's able to calculate the total amount of CO2 to build the house.

The summary for the straw would be that the main properties that it has to achieve are the density (between 110 and 150 kg/m3 to have 0,055 W/m2K of thermal conductivity), the moisture has to be below 15% and CO2 emissions per kg of straw is -2.197 kg/kg.

VIII. Architecture The internal placement of the different parts of the building (kitchen, living room, restroom, stairs‌) was studied according to the orientation of the house to the sun.

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The places like living room and bedroom should be facing South to have more sunlight and better temperature and kitchen, bathrooms, access zones, among others should be placed on other parts of the building.

Facing north will be a window that goes through all the wall just above the stone structure and below the start of the roof. According to the client’s budget,it can be many windows side by side, because a big glass window with the proper canvas can be more expensive.

Previous solutions Before having the final design, there was made more than 10 different layout solutions. All of them were made according to the passive house principles but the client’s taste always prevail.

That’s why it was established that it should be done the best design possible to have a good energy behavior, sustainable materials and functional design. The option presented below was made regarding a better space quality sacrificing energy savings. At this point the walls had a different way to fit each other that later was substituted by the final option.

Ground floor:

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1st floor

Faรงades PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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Cross section

Number of floors Because a passive house should be as compact as possible, it was decided that a house with almost 100m² will be more energy efficient if it is used a 2 floor configuration with 30º pitch roof. In spite of having the attic, it can only be accessed from outside of the house and will not be heated.

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Wall thickness At the joints and the rest of the wall it is not possible to have the same member member from the outside to inside because it will act as thermal bridge.

The thickness is determined by the Ν -value of our main insulation material – straw and this combined with the other materials should result a combined U-value smaller than 0,1.

Wall configuration It would be easier to assemble walls with 1m and 1,5m wide due to lighter weight and smaller size. Also for transportation it would bring major advantages. On other hand only 1 meter width wall parts does not allow to introduce windows and doors and at the same time fulfill the regulations for passive houses, due to airtightness and possible thermal losses. But for smaller windows such as toilet windows it is possible to include them on 1.5m wide walls.

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The wall ends has a cork sheet that allow a better connection between the different prefabricated parts, which assures the airtightness and a desirable thermal behavior on the joints. It is also easy to assemble, at the corners the ground floor edges should mismatch the ones on first floor in order to get a better structural behavior. That wasn’t possible to achieve because there are just 2 sizes of panels (1m and 1,5m), that’s why it will be used special connection plates that will be studied more in detail on the structural section.

Ground floor The ground floor has the kitchen on the West side with access to a small storage room where can also be the washing and drying machines facing north.

All the areas mentioned are inside the pre-existent walls, the new part of the building on the South side is the living room, where the South and west side are mostly covered by glass and have a timber wall on the East side.

First floor The first floor plan was based on a functional south facing concept that allows the users to have light for their daily activities, increasing the space quality.

When the user comes from stairs, he will have a south facing window with an office that can later be changed to another bedroom if the number of persons also increase.

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Stairs The stairs were placed on the North/West corner of the house to use space that has less desirable characteristics for a bedroom or Livingroom such as smaller amount of sun. It will be made of timber.

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Roof The roof is made out of ceramic clay tiles, not only because of its cheap price and easy application but also because it has a low environmental impact. The pitch of the roof will be 30ยบ, to South direction, which allows to have the same height of panels on the higher side of the roof.

This also has a good angle to have an optimal area of solar panels applied in a parallel position with the roof, without disrupting the visual aspect of the building.

IX.

Structure

Dead loads A dead load is the constant weight of a structure, including the structure itself, along with the devices intended to be permanent. When structures are designed, the architect can make a simplified dead load calculations to ensure that the structure can support itself. In addition, the weight of variable live loads that

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change or move over the life of the structure must also be considered. Failure to account properly for the loads on a structure can result ultimately in collapse and/or other smaller problems.

Weights of permanent equipment, such as heating systems and other installations which are usually obtained from the manufacturer are also considered as self weight.

The dead load is not supposed to change over the life of the structure.

There is standardized information and estimates about known building materials to calculate as closely as possible.

In order to calculate it, it is necessary to know the thickness and weight per square (or cubic) meter.

For dead load calculations it was used the following weights:

Roof Material

Weight KN/m²

Straw layer (1m)

1,5

Asphalt layer

0,1

moisture membrane

0,05

airthight membrane

0,05

timber structure

0,7

internal cover

0,2

shear force cables

0,1

TOTAL

2,7

Walls Material

Weight KN/m²

Straw layer (0,5m)

0,75

Outer wall cover

0,15

Timber Structure

0,3

moisture membrane

0,05

airtight membrane

0,05

internal cover

0,2

shear force cables

0,1

TOTAL

1,6

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1st floor slab Material

Weight KN/m²

Straw layer - sound (0,1m)

0,15

Upper slab cover

0,15

Timber Structure

0,5

lower slab cover

0,2

shear force cables

0,1

Services (pipes, vent...)

0,2

Partition walls

0,85

TOTAL

2,15

Partition walls Material Straw layer - sound (0,1m)

Weight KN/m² 0,15

timber structure

0,1

wall cover (2 sides)

0,2

TOTAL

0,45

TOTAL per m² (1st floor)

0,85

Live loads By contrast, live loads are flexible and they will change over time. They also impact structures in different ways, in addition to weighing down the structure, they also strain it as they move around.

 On the stair top platform it is the normal slab but we use the value for the stairs because part of the stair loads come to that element

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Snow loads For the chosen building location in Denmark and for the one pitch roof building such as this, the snow load is 0,8KN/m².

X.

Seismic Design

One of the downsides of the concrete and masonry buildings, is the high mass, which can be a problem for the ground accelerations done by the seismic activity. Unlike concrete, Timber structures are light and have a very good weight to resistance ratio. In Denmark The low inertia of a timber building makes it easier to keep up with the ground movements, limiting greatly the damage.

Basic design principles -

Structural Simplicity

Transmission of forces through clear and direct paths - bigger reliability in predicting seismic behavior -

Uniformity and symmetry

Regular distribution of the structural elements in plant short and direct transmission of seismic forces -

Uniformity of structure height

Avoid members with a high concentration of forces and areas with high ductility requirements which may cause premature collapse -

Strength and bi- directional rigidity

Use of structural elements that resist horizontal loads on any direction (seismic action is a bi -directional phenomenon) it is important to choose the more rigid places to: - Minimize the effects of the action - Limit the development of excessive displacements (control damage)

Strength and torsional rigidity It will limit the development of torsional movements which lead to non-uniform forces PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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e0 ≤ W x 0.30 x r where: e0 – distance between the mass center and the rigidity center r – Torsion radius: (torsion rigidity/lateral rigidity) 1/2 r ≥ ls

-

(ls – gyro radius of the floor mass)

Diaphragm action at the level of the floors

Ensure the transmission of seismic forces to the vertical structural systems and make sure that these systems act together in resisting those forces

Adequate foundation Ensure that the building is uniformly affected by movement of soil - Place the structure in the same type of soil - Use the same type of foundation - Enter joints to separate bodies with different foundations (used mostly in big buildings – L>30 meter)

Structural Regularity

This building has a very uniform shape and it is also regular in height, which according to the table, it is needed to make a plan model and Static Analysis and there’s no need to reduce the overall resistance.

As the calculations for the wind, it is necessary to have some concerns about the seismic action. For the Eurocodes, this concerns are:

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-

Location;

-

Type of soil;

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The soil considered has medium characteristics which makes it a class A with a medium cut wave velocity between180 and 360 m/s.

-

Near earthquake:

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-

Far earthquake:

-

Building importance class

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The building has importance class II.

MODAL ANALYSIS (simplified method) The first thing is to calculate the mass for each kind of freedom. Roughly speaking, it is needed to get the mass per floor (biggest mass on horizontal direction). After finding the mass, it is needed to make the mass matrix [M], and also the rigidity matrix [k].

The calculation for the rigidity matrix is calculated though the unitary displacements in each type of freedom.

It is also needed to calculate of the frequency, the angular frequency (Wi) and the cyclic frequency(fi).

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



Angular Frequency: det k   W 2  M   0

From this we obtain the Pi values, in the same number as the freedom degrees.

This way it is possible to get the cyclic frequency.

Now it’s time to calculate the vibration modes, in this way:

k   P  M  v  0 2

i

i

Through the vibration modes we can predict the way the building behaves in each mode.

It is followed by the treatment of the vibration modes, i  , which is determined by the following formula:

i  

v  i

v   M  v  i T

i

The modal participation factors come from the vibration modes through the following formula:

Pix  i   M  1x T

Based on cyclic frequency, zone, type of ground and type of structure it is possible to get the accelerations and response spectrum.

Sa  Sa' From the acceleration and frequency it is possible to reach the displacement in each freedom degree, Sd i , from the following formula:

Sd i 

Sa

2    f i 2

This way is possible to determine with a good grade of sure the effects of seismical activity on a structure with hand calculations. In this case it is not necessary to do by hand because the software Robot Structural Analysis can do it accurately.

Safety factors regarding the loads According to Eurocode 0 (EN 1990) for the calculation it is necessary to multiply the forces for safety factors.

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XI.

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LOAD COMBINATIONS

Because there are different kinds of load acting on a building, there are many combinations that can be made, with the objective of covering all possible situations.

This includes Self weight, Utilization active loads, accidental loads, wind in different directions, seismic in different directions, intensity and also seismic waves with different frequency and resistance loss due to fire.

XII. WIND CALCULATION BASIC WIND VELOCITY The area where the building will take place is 24m/s.

AERODYNAMIC RUGOSITY OF THE TERRAIN The variation of the wind speed depends a lot from the presence of obstacles that affect the air flow. To take into account this situation the Eurocode 1 defines 4 different kinds of terrain, that are shown on the next table:

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According to the table, the building is in a terrain category II.

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WIND VELOCITY AND DYNAMIC PRESSURE Once defined the local characteristics of the structure (zone and type of terrain) it’s time to calculate the wind speed, given by:

Dynamic Pressure (qp) With the same procedure, it was made the calculations for wind on other parts of the building (different “z” values). The z values correspond to the height of the wind from the ground. The highest point of the building is at 7m.

To calculate the pressure according to the coefficient Cpe1 (for areas smaller than 10 square meter) and Cpe10 (bigger than 10 square meter) there is the scheme 7.4 and table 7.1 on Eurocode 1-4.

The Cpe depends on the wind direction, configuration of the surface and it will have positive values when the wind makes pressure directly on a surface and negative values when there is suction (generally on the opposite side of the building).

To get the final wind pressure according to the coefficient:

Vertical wall pressure (KN/m²)

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Wind loads for vertical walls KN/m²

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North

South

East

West

Wind pressure (qp)

1,0

1,0

1,0

1,0

Coefficient (direct wind)

0,4

1,0

0,8

0,8

Positive load (direct wind)

0,43

0,96

0,77

0,77

Coefficient (suction wind)

-0,3

-0,7

-0,5

-0,5

-0,27

-0,67

-0,48

-0,48

Negative load (suction wind)

The calculation from external wind loads regarding the roof according to the Eurocode 1, section 1-4 are:

Measurements for wind direction = 0º

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With all the measurements for wind direction = 90ยบ

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With all the measurements for wind direction = 270ยบ

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Wind loads for rooftop KN/m²

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Zone F

zone G

zone H

zone I

Coefficients for external pressure

-2,5

-2

-1,2

0,2

Wind pressure load (qp)

0,96

0,96

0,96

0,96

Wind pressure (KN/m²)

-2,4

-1,92

-1,152

0,192

INTERNAL WIND LOADS According to Eurocode 1 – section 4, the internal wind pressure is generally calculated according to the openings on a building’s façade and cover. The building openings include small dimension openings as opens windows, ventilators, chimneys, among others.

Even in a completely closed constructions and especially on Passive Houses it is needed to foresee the internal pressure resulting from a secondary permeability because of the air leaks from door, window and other kind of devices.

To calculate the internal pressure coefficients “cpi”, the EC1 defines the opening index µ (7.2.9; p. 56). But it refers that when it is not possible tocalculate the µ value for a specific case, or the other values doesn’t apply, the Cpi should be considered as the worst value between: PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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To make sure which one is the worst situation, according to the load combinations, support conditions both the cases were introduced on the software model. The case b was the one that had bigger values.

To introduce the values on the model, it was necessary to do the following calculations for a flat roof building of the roof in order to fulfill the EC1 rectangular building demand.

Straw in the walls – structural?

Straw buildings with no other structural elements inside are not taken into account on the Eurocodes.

Because it is not an homogeneous material, lacking quality control, its resistant values are variable with type of straw, humidity, density, compression rate, among other. This makes of it an unreliable building material according to the regulations. That’s why the straw resistance will be not taken into account on the calculations.

The lateral walls facing East and West surrounding the attic (image below) are not meant to be structural and insulated and will have only a simple structure that only needs to resist wind forces.

The attic wall facing North (image below) will not be insulated but it is structural to deal with the forces coming from the roof. The panels used there are almost the same as all other walls (height and width) but they are not insulated.

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Beams over doors and windows The beams over doors and windows are small (biggest beams have 2m long) and the calculations regarding this were made on software Robot, which can be found on structural annex.

Roof The roof will be made out of ceramic tiles + timber structure. This will have timber beams, purlids and tiles.

It’s simplicity to mount means that there’s no need to make prefabricated panels. It will be calculated as a simply supported beam and its manual calculations will not be extended to detail here because it is done with the same principle as the stairs beam calculated below. In fact the calculations for the roof beams has smaller complexity than the stairs beam/handrail, it can be done with the aid of the software Autodesk Robot Structural Analysis. There will be made some simpler calculations to make sure the sections gave by the software are correct. The section of each beam will be 200x100mm.

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1st floor slab The first floor slab has Timber beams with distance of 1 meter between each other. The Span between supports is 6m, which doesn’t justify the use of a middle support.

The slab will be made out of 1x6m panels which has one beam on each side.

Beam calculations on annexes, the section is 300x200mm.

XIII. Fire This study Fire Safety in Building Dansk Standards (DS) refers to a space that generally takes housing characteristics, being however possible to adapt it to a space for tourism, integrated into a hotel and then, arises the need for having a fire study.

Building Insulation Materials According to the Danish building regulation BR95 part 6.7.5. insulation materials have to be noncombustible. This requirement excludes the use of plastic based insulation materials in general. There are however some exceptions mentioned in the building regulation. If combustible insulation materials are used there are no fire requirements which necessitates the use of BFRs. Walls and ceilings Products used for walls and ceilings are regulated by DS 1065-1, Fire Classification - Building materials Class A and Class B materials which divides the materials in two different classes: Class A materials which are

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- Slightly ignitable - releasing a slight amount of heat and - generating a slight amount of smoke Class B materials which are - Normally ignitable - releasing a normal amount of heat and - generating a normal amount of smoke

The house in this case study is a Class B material.

Thus, on a brief overview of the entire space, there is not a need to consider the actual analysis, i.e., the maximum number of people who may be simultaneously on the space, since it is a very small scale.

So, in general it is therefore needed to consider which are the escape routes, to ensure that the space has all conditions to ensure efficient evacuation in case of fire.

It is also important to note the necessity of resistance of exterior walls, which should consist of materials that guarantee a minimum resistance of 30 minutes since it is a single building, no contiguous fractions, otherwise, it would have to guarantee resistance 60 minutes.

Since the object of his case study is a small residential building without abnormal features except the use of straw as insulation, it is not needed the execution of emergency exit plans with escape routes or fire extinguishing device plans.

Structural concerns regarding fire A structural timber member that is exposed to fire has the section diminished 0,2mm per minute (this value depends on the flammability of the materials around).

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According to the building’s class of fire (30min) there is a 3mm section loss (0,1mm x30 min), which means the beam needs to be 3mm bigger all around the section.

XIV.

Panel design

For the final panel designs it has been considered how compact the panel is, the structural wood has to be a part of the panel itself, it has to be easy to install during the erection of the building, it also has to include the straw inside in order to install it easily and faster. The gains of doing panels are several, first of all, the construction time is much lower than a normal brick house, transportation of the materials is easier, and the work in the field is almost 10 times faster than a normal construction. It is also considered the possibility of making different houses with the same panels always, and that means the panels can be built and then installed in few days because they can be stored. The connection between they is easy and it can be assembled by almost everyone. The density of the panels is lower than a brick wall density, in order to that, the requirements for foundations are less and in fact, it reduces the cost. Designs places in aannex‌.

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Figure 9 3D explosion view of the panel and 3D view of the panel

As It can be seen in the 3d views, the straw is going to be fitted inside the panels, because of the compression the straw is going to expand where there is no wood to hold it, that means, it the whole faces the straw will be at the same level as the wood but not in the inside face. The solution for the inside face is to put a net between the columns and fill it up with non-compressed straw, which will have a different lambda value because the final compression is not going to be known, the value for this straw is going to be 0.08 W/mK instead of 0,055 W/mK as it could have been seen before in the straw properties.

The small pieces shown in figure 4, are pieces of cork, which will help to reduce the possible thermal bridge of the wood and thanks to the compressibility of the cork it will help to compress the straw even more once placed inside the panel.

As a first option before consult anything with the experts Lars Keller and Jens Peter, the wall was composed by: PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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Ventilated façade (material chosen by the client) Waterproof membrane OSB (waterproof and airtight) 18mm thick Panel Plaster COB 30mm thick

Total thickness of the wall installed in the south façade: OSB (18mm) + Panel (620mm) + plaster (30mm) = 6680mm Total thickness of the wall installed in the north, east and west façade: OSB (18mm) + Panel (570mm) + plaster (30mm) = 6180mm Without taking into account the ventilated façade, with it can be different measures depending on the client.

But because of the possible condensation and the recommendations of the experts the final solution is going to be:     

Ventilated façade (material chosen by the client) Plaster Klimasan-W (20mm) Panel Plaster Weber.cal 173 (20mm) Plaster Weber.483 (3mm)

Total thickness of the wall installed in the south façade: Klimasan-W (20mm) + Panel (620mm) + plaster Weber.cal 173(20mm) + Weber.pas 481 (3mm) = 6630mm Total thickness of the wall installed in the north, east and west façade: Klimasan-W (20mm) + Panel (570mm) + plaster Weber.cal 173(20mm) + Weber.pas 481 (3mm) = 6130mm

As it can be seen in Annex 9 the 3D view shows an empty space between the wood columns in both side, exterior and interior, this space is going to be filled with non-compressed straw (more than non-compressed is not going to be possible to know the total compression of this straw so it is going to consider non compressed for the thermal insulation values (0.08 W/mk instead of 0.055 W/mk).

XV.

Other possible insulation materials

The consideration of other materials is done in order to complement the straw as an insulator and try to avoid possible thermal bridges where the panels are joining. Also, the studied materials must be as natural and close, avoiding the transportation contamination, as possible. No one of them is structural. And not all of them are going to be applied in the building.

Cork

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Figure 10 Cork boards (Amorim Isolamentos (Company), s.f.) (Cork Link (Company), s.f.)

The cork is mainly produced in Portugal, and the first clue of this is the distance from Denmark because it increases the CO2 emissions during the transportation. On the other hand, cork had been selected in this case because it doesn’t have chemicals, it is 100% cork, and the density is really low: 110 to 120 kg/m3, it is easy to install and it doesn’t need an expert. The thermal conductivity is λ = 0,037 to 0,040 W/m°C, the compression resistance at 10%: ≥ 100KPa, excellent dimensional stability, fire resistance: Euroclasse E, which ensures that the material is flame retardant, easy to cut and fit in the wall and it is 100% recyclable. Sink CO2 (carbon negative), low embodied energy and no emission of harmful compound for indoor air quality.

Prices cork without taxes and shipping: 50 mm thick: 11.76€/ m2 + taxes  88.2DKK/m2 75mm thick: 17.64€/ m2 + taxes  132.3 DKK/m2 100mm thick: 23.52€/m2 + taxes  176.4 DKK/m2

Sheep wool

Figure 11 Sheep wool as insulator (EcoMerchant, s.f.)

Sheep wool offers excellent sound absorption properties for many acoustic situations with high requirements and also a good thermal insulation with a low lambda value. The natural fibers of the sheep wool have a self-combustion temperature of 560 – 600°C. This is around twice as high as that of wood (270°C). Sheep wool products need no additional flame inhibitor and achieve outstanding values in the European and Swiss standard fire tests, therefore generates no poisonous gases in the case of fire, is class E which ensures that the material is flame retardant. Sheep wool can absorb up to 33 % of its own weight in moisture, without compromising its insulating effect.

The density is around 20 kg/m3 and the lambda value in between 0,035 and 0.04 W/m2K. Also is an excellent sound insulator, biodegradable and recyclable.

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Most of the sheep wool would come from UK, which means CO2 emissions during the transportation, the CO2 emissions due to produce it is -0.53 kg/kg (without the transportation emissions). Is not far away from Denmark, the option will be considered.

Table. 5 Main properties of sheep wool (Therma Fleece (Company), s.f.)

Price: Thickness of 50mm 81.15 DKK/m2 Thickness of 75mm 121.73 DKK/m2

 

10.82 €/m2 + taxes + shipping 16.23€/m2 + taxes + shipping

Wood fiber board

Figure 12 Wood fiber (Gutex , s.f.)

Is obtained using sustainable forestry practices but with chemical additives: Polyolefin binding agent and Ammonium polyphosphate compound as flame retardant. The advantages are the inherent elasticity makes it extremely adaptable, provides excellent thermal insulation with a thermal conductivity value of 0,038W/m2K, superior thermal storage capacity provides outstanding insulation against heat in the summer and cold in winter, improves acoustic insulation, quick and easy installation, PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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regulates humidity, water vapor diffusion permeable, the wood is a sustainable and recyclable natural resource and it is biologically safe (natureplus® certified).

Table. 6 Gutex Thermoflex properties (Gutex , s.f.)

Prices:

Table. 7 prices for Gutex Thermoflex insulation (Gutex, s.f.)

Panels 40 mm thick (it can’t be chosen 50mm thick) cost 43.5 DKK/m2.

Recycled loose cellulose (Warmcel) PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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Figure 13Warmcel insulation (Warmcel, s.f.)

This material is manufactured from recycled newspapers and chemical additives, those additives are mainly inside the newspaper itself (ink and another substances) with means that no extra chemicals are going to be used during the production of the material. This material is coming from UK so it has to be considered the transport CO2 costs. The advantages are: ozone depletion potential Zero, Free from CFCs (Chlorofluorocarbons) and VOCs (Volatile organic compounds), the thermal conductivity (λ) = 0.038 W/mK in lofts (tested in accordance with BS EN ISO 10456:2000), exceeded BREEAM Green Guide rating ‘A’ (0.005 Ecopoints), extremely resistant to fire through the addition of simple inorganic salts, and it is recyclable.

Warmcel 100 is non-toxic and non-irritant to eyes and skin. However it does cause a small amount of dust when pouring, therefore is recommended you wear a dust mask. During the installation is recommended to try to keep the cellulose approximately 150mm away from any hot component, high amperage rated cables (shower and cooker cables) must be kept away from any insulation material.

Energy Efficient: Warmcel has a ‘better than zero’ CO2 rating. The energy sequestered in the product exceeds that in the manufacture, installation and removal of the product at the end of its lifecycle.

Fire Performance: Through the addition of inorganic salts, is extremely resistant to fire Safe in Use: Warmcel contains no harmful additives and considered to be nonirritant. Will not react with other common building components such as copper pipes, electric cabling and metal nail plate fasteners.

Thanks to the addition of inorganic salts, is resistant to biological and fungal attack, these salts also make the product unattractive to insects and vermin.

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Table. 8 Warmcel properties (Warmcel (company), s.f.)

Prices:

Table. 9 Warmcel prices (EcoMerchant, s.f.)

Each bag covers 5 m2 to a depth of 50mm of cellulose and costs 63 DKK + shipping.

Exterior Impermeable layer Two other materials might be used as an impermeable barrier and one of them as an airtight layer due to fulfill the passive house criteria. Both recommended by Farhaus Passive House Construction Company.

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Gutex Multiplex-top The chosen material to use as an impermeable layer against the rain from outside is “Gutex Multiplextop”, directly recommended from the passive house construction company “Farhaus”, they used and the experience using it is positive.

This material doesn’t need to be an insulator from the heat, but it also provides us some resistance against the thermal conductivity (0,044 W/mK).

Figure 14 Gutex Multiplex-top (Gutex, s.f.)

Table. 10 Prices Gutex Multiplex-top (Gutex, s.f.)

The price is around 72 DKK/m2 + shipping and taxes.

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Table. 11 Gutex Multiplex-top properties (Gutex, s.f.)

OSB panels

Figure 15 OSB Panel

OSB panel is a chipboard panel, composed of long, thin strips of wood arranged and oriented in layers, it has natural wood properties without any chemical additions because the glue to fix the strips is made of natural resins. It would work as an airtight layer in the wall and the roof, as the plaster doesn’t guaranties that. The thermal conductivity of the OSB panel is 0.12 W/m°C and the thickness to be sure that is airtight and waterproof is going to be 18mm (directly recommended from the passive house construction company “Farhaus”). It might be installed in the outside of the wall and it will support the structure as it is strength enough and it will help to support lateral charges.

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Also, with this material is going to be installed a ventilated façade thanks to the good structural properties of OSB. It is going to be used as an impermeable layer to avoid the water in the straw, the main characteristic for the vapor resistance is µ =300.

Properties

Unit

Thickness (mm)

3

8-10 680

>10 - <18 660

18 - ≤25 640

>25-28 640

Density

Kg/m

Resistance to flexion (longitudinal) Resistance to flexion (transversal) Elasticity module in flexion (longitudinal) Elasticity module in flexion (transversal) Cohesion

N/mm2

30

28

26

24

N/mm2

16

15

14

13

N/mm2

4800

4800

4800

4800

N/mm2

1900

1900

1900

1900

N/mm2

0.5

0.45

0.4

0.35

After boiling water test

N/mm2

0.17

0.15

0.13

0.06

Swelling

%

≤12

Humidity

%

5 - 12

Table. 12 OSB properties (Centre Materiaux Ecologiques, s.f.)

The price id given from Farhaus Company because it had been impossible to get it from the company directly and it is around 75 DKK/m2.

Plasters Natural plaster It has been studied also the natural plaster, the natural plaster is made of sand ⅗, clay ⅕ and fibers ⅕ which is straw cut in maximum 2 cm long and also some hemp fibers, which are very thin but quite strong, it can also be used hair for example. The resource of this information is Jens P. Mølgaard who is living in a Straw house in Denmark, and from his experience the plaster could be analyzed as good material for the building.

The plaster is a combination of materials with different properties, the possibility of Do It Yourself is not going to be considered because in order to fulfil the passive house standard and achieve a perfect finish inside the house. Is not going to be considered the DIY material because as far as it is a passive house for sell to a client is going to be necessary to guarantee the quality of the materials.

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One of the advantages of this material is the airtightness, with enough thickness and well installation, this materials acts as an airtight layer, but as far as is not known exactly how much thickness and it doesn’t guarantee that during the construction this thickness it has been achieved, the final consideration is to not consider this material airtight. Another advantage is the thermal mass, is a dense material and it has the possibility of store heat in it when the temperature of the house is higher and give it back when drops down.

Two different clays are going to be considered: The COB is made of clay, shorter and thinner barley straw fibres and various sands. The thermal conductivity is λ = 0.40 to 0.50 W / mK, density 900 to 1100 kg / m³, with 1 ton of this material is going to be able to plaster between 15 and 20 m2 of wall with 5 centimetres thickness. The proportion between water and the COB clay is every 3 kg of clay is 1 litre of water. It is 100% natural and carbon negative.

Figure 16 COB once plastered (Argilus, s.f.)

ISOL’ARGILUS is a natural plaster with a Lambda of 0.06, it must be applied in 2 or 3 layers of 4 cm each maximum. The mix of Perlite/clay/lime will give an excellent application. The plaster is 100% natural and carbon negative.

Prices per 3 centimeters layer: COB: 25kg Bag – around 1m² per bag – 112DKK/m2 - 14.92€ per Bag +transport from France 1000kg Big – around 30m² per bag – 314.29€ per Big Bag, 10.47€/m2 +transport from France

Isol Argilus: 50L = 10Kg bags - Around 1m² in 4cm thick – 183 DKK/m2 - 24.40€ per Bag +transport from France.

More plasters have been studied, and as is going to be shown later, they have a huge impact to the final solution, and that’s thanks to the vapour conductivity through the plaster and the final airtight given from the plaster (thanks to Lars Keller, straw bale house builder since 1997 advices). The plasters will improve the condensation within the layers in the wall as it can be seen in the figure…..

The following plasters will be chosen as a final design for the wall due to the perfect conditions for the condensation, heat transmission, breathability and thermal mass.

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Weber.cal 173 It is a mineral lime plaster for interior and exterior. It has a high resistance to the cracking thanks to the fibre reinforcement.

The components of this materials are the Hydraulic lime, classified mineral aggregates, organic lightweight aggregates, air-entraining agents and cellulose fibres. It can be prepared by machine or by hand, as it was said before, is moisture regulator. No additives are mixed with the main materials.

It is going to be used on the interior face of the wall, touching the straw with a thickness of 20mm as the product can’t be thicker.

The total weight in kg per m2 if the thickness is 20mm is going to be 20kg/m2.

Table. 13 Data table for weber.cal 173 (Weber, s.f.)

Weber.pas 481 Aqua Balance It is a finishing layer for exterior and interior with permanent protection against algae and fungi.

Is a Ready-Monomass, is according to EN 15824. The composition of the plaster is Silicone resin, organic binders, mineral aggregates classified, additives for a better workability and adhesion on plaster base, highquality pigments and it doesn’t contents biocides façade preservation (film preservation).

This layer is going to be installed after the Weber.173 and with a thickness of 3mm, as a last layer before the inside of the house. The good permeability is going to help for the condensation in the wall and as it will be seen in the figure number… the relative humidity in the wall is going to be enough in order to have a good durability of the wall without moisture.

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Table. 14 Data table for weber.pas 481 Aquabalance (Weber.pas, s.f.)

The consumption of this material applied to the project is going to be:

Table. 15 Quantities for the installation of the plaster per m2 (Weber.pas, s.f.)

Klimasan-W It is a highly thermally insulating plaster for outdoor use, environmentally friendly and pure mineral. The ecobarrier wall is a homogeneous composite of pure natural materials. Is going to be used in the exterior part of the wall, just between the ventilated façade and the panel due to achieve a good thermal values and also for the breathability of the wall in order to not condensate inside the straw and affect the materials of the panel.

The total thickness installed is going to be 20mm.

Data Thermal conductivity

0.077

W/mK

Density

300

Kg/m3

Compressive strength

1.6 to 3

N/mm2

Flexural strength

0.8

N/mm2

Water vapour diffusion resistance

Âľ =6

Elasticity modulus

2000

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N/mm2

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Building class

A1 >3kg/m2 h0,5

Water absorption coefficient Bag contents

50

Litres

Water requirements

15

Litres

Total amount per 50L bag

41

Litres

Price

15,50

â&#x201A;¬/m2 EXW

116.25

DKK/m2 EXW

Table. 16 Klimasan-W properties (Klimasan, s.f.)

Comparison between the insulation materials Material

Cork

Sheep wool

Wood fiber board

Recycled cellulose Warmcel

OSB 4 18mm

Gutex Multiplextop

Natural plaster COB and Iso Argilus

Thermal conductivity W/mK

0,037 to 0,040

0,037 to 0,039

0.038

0.04

0.12

0.1

0.4 / 0.06

Fire reaction

Class E

Class E

Class E

Class E

Class D

Class D

-

Airtightness

No

No

No

No

Yes

No

Possible

Waterproof

No

No

Yes

No

Yes

Yes

-

Density kg/m3

110-120

20

45

60

640

625

900 - 1100

Additives (chemicals)

No

No

Yes

Yes

No

No

No

Precedence

Portugal

UK

Germany

UK

Luxemburg/ Germany

Germany

France

Recyclable

100%

100%

Yes

Recycled material

Yes

Yes

100%

Durability (years without any change)

50-60

The life of a building.

-

-

-

the life of a the life of a building building

CO2 negative?

Yes

Yes

-

Yes

-

-

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Uses

Horizontal and vertical

Horizontal and vertical

Horizontal and vertical

Horizontal and vertical

Horizontal and vertical

Horizontal Vertical and vertical interior wall

Price (50mm thick) + taxes+ shipping

88.2 DKK/m2

81.15 DKK/m2

43.5 DKK/m2 (40 mm thick)

12.6 DKK/m2

75 DKK/m2

72 DKK/m2 183 DKK/m2

Table. 17 Comparison between natural materials that can be used

Membranes and plastic materials Airtight tape Pro Clima Tescon Vana Is used to form a secure airtight and waterproof between foil and fleece membranes (vapour checks and airtightness membranes, roof underlays and wall membranes) and joints between membranes and smooth, non-mineral surfaces. Is also suitable for sealing butt joints between wood-based panels such as OSB or MDF sub-roof panels. As it can be seen in the Passive House requirements, the airtightness of the house is one of the most important values to achieve the Passive House Standard, so in order to achieve it, the tape has to fit perfectly and donâ&#x20AC;&#x2122;t let any leak of air entry to the house.

Fig. 2 Technical details of the tape

Fig. 3 Tape to guarantee the airtightness and applied (EcoMerchant, s.f.)

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Price: 225dkk/30 meters tape

Airtight membrane One of the principles for a Passive House is to have a high airtightness level. That means to design and install a layer around the building envelope due to eliminate unwanted draughts, saving energy and reducing the Carbon emissions during the lifetime of the building. The membrane studied also ensures the interstitial condensation minimizing it, due to not have any damage because of the moisture.

The chosen membrane is Intello Plus, which provides a high diffusion tightness during the winter and a maximum diffusion openness during the summer, the gain would be an ideal protection against condensation in winter. It is translucent, easy to install and recyclable. The tape will be needed in order to join the membranes between them.

The price is around 25 DKK/m2

Fig. 4 Airtight membrane in a roll and applied (EcoMerchant, s.f.)

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Fig. 5 Airtight membrane installed in straw house in Friland (Denmark)

XVI.

Final chosen materials for the interior and exterior faces of the panel

After analyze the possible solutions for the last layer of the panels due to have no condensation, no moisture, good thermal insulation, structural stability, good thermal mass and breathability (it has been checked by the online program www.u-wert.net), and receive the recommendations of the experts Lars Keller and Jens Peter Mølgaard the final solution would be (from exterior to interior):    

Ventilated façade(material chosen by the client) Klimasan-W plaster, 20 mm Panel Weber.cal 173 20mm



Weber.pas 481 Aqua Balance 3mm

Figure 17 Materials of the wall (U-Wert, s.f.)

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1) Weber.pas 481 AquaBalance (3mm)

2) Weber.cal 173 (20mm)

3) Straw panel 5) Ventilated façade

4) Klimasan-W (20mm) 6) Wood or another material chosen by client

This materials are fitting with all the considerations taken before. It could seem strange to do not have a waterproof membrane or an airtight one, but the moisture goes from inside to outside, that means that the interior plaster has to be more waterproof than the outside one in order to let pass the vapour through the wall. The thermal conductivity is also important, the main material to improve it is the straw which is in the panel, so for the outside and inside layers of plaster is almost not taken into account as an important property. Also, for the outside face, it has been installed a ventilated façade, the important point of it, is to do not have direct contact with the water from outside, also it provides a finish design that it can be chosen by the client he or she has more options in order to choose one or another design. The structure of the ventilated façade is fixed to the panels and it makes more strength stability for the possible horizontal loads.

As it can be seen in the figures….

The result of the condensation calculation is significantly influenced by the following factors: 

  

The indoor and outdoor temperatures and the corresponding relative humidity, where the dry and warm temperatures are probably favourable. The values depend on an indoor 20 ° C, 50% humidity. Outer-0.4 ° C, 80% humidity. The temperature is -0,4ºC in fact of the humidity freezes under this temperature.

Of the water vapour diffusion resistance μ numbers of building materials used, the state is usually a lower and upper limit, for example μ = 5/10.

From the temperature profile within the component and the thermal conductivity λ of the building materials used.

The length of the winter and summer evaporation period is per 90 days. For the evaporation period the climatic conditions were in accordance with DIN 4108-3: 2014-11.

Figure 18 Wall characteristics (U-Wert, s.f.)

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Figure 19 Relative humidity in the wall (U-Wert, s.f.)

The relative humidity never arrives to 100% and that means is not going to place moisture in the wall.

Thanks to the insulation, the interior part of the wall is not changing the temperature values during the day, either if it is to warm or to cold outside. As it can be seen in the next figure.

Figure 20 Temperature changes during the day (U-Wert, s.f.)

The temperature inside the wall is not changing anymore in some point of the insulation, which means the insulation is good enough from this point in order to do not have thermal bridge at all.

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Figure 21 temperature variability between outside and inside (U-Wert, s.f.)

Temperature profile within the component at different times. Respectively from top to bottom, brown lines: 15, 11 and 7 clock and red lines by 19, 23 and 3 clock in the morning.

For a good summer heat protection materials should be used with a high heat storage capacity, ideally in combination with an external insulation. In addition, the direct solar radiation must by means of window shading devices, be reduced to an acceptable level.

XVII. Final chosen materials for roof The roof is going to be with one slope, the idea is to have a ventilated roof, the main insulation is going to be at the slab, not at the slope because with this solution is going to be used less panels, and that means less money, and also, the building is going to be lighter. However, one of the most important part of insulating the slab is to reduce the total surface in contact with the exterior. The total slope decided is 25.4º in order to put an entire panel in the other side of the slope (North face). Also, the final solution of the materials it has been considered in order to make it accessible to the people if someday is desired.

Slope (from exterior to interior):   

Tiles Beams Main beams

Figure 22 Example roof for the building (Google, s.f.)

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Figure 23 Example roof for the building (Google, s.f.)

Slab (from exterior to interior):     

Chipboard (16mm) Panel Cork (30mm) OSB 4 (18mm) Warmcel insulation

Figure 24 Materials detail of roof slab (U-Wert, s.f.)

Figure 25 Characteristics of the roof slab (U-Wert, s.f.)

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Under the conditions exposed in the roof, and taking into account that the temperature of the inner surface is going to be 19.5 °C and a relative humidity of 52%, any mould is going to show up in the roof, neither condensation. For the moisture it can be seen that is also not appearing at all.

Figure 26 materials in the roof detail (U-Wert, s.f.)

Figure 27 temperature variances during the day (U-Wert, s.f.)

Temperature profile within the component at different times. Respectively from top to bottom, brown lines: 15, 11 and 7 clock and red lines by 19, 23 and 3 clock in the morning.

For a good summer heat protection materials should be used with a high heat storage capacity, ideally in combination with an external insulation. In addition, the direct solar radiation must by means of window shading devices, be reduced to an acceptable level.

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Figure 28 temperature changes in interior and exterior of the house (U-Wert, s.f.)

As it can be seen with the blue line, the temperature inside of the dwelling is going to be constant thanks to the thermal insulation.

XVIII. Final chosen materials for the ground slab The ground slab is going to be composed by:    

Parquet (20mm) OSB 4 (18mm) Warmcel (250mm) Cork (30mm)

But one off the most important parts of the insulation is going to be the foundation itself, with the low lambda value of the mussel shells is going to be achieve a comfortable U-value. (Is not taken into account in the program calculations).

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Figure 29 materials for the ground slab (U-Wert, s.f.)

Figure 30 characteristics for the ground slab (U-Wert, s.f.)

Figure 31 relative humidity in the ground floor (U-Wert, s.f.)

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As it can be seen in the figure…………. Thanks to the airtightness and vapor barrier of the OSB, the condensation and both the moisture and mold are not going to be present in final solution of the ground floor slab.

The surface temperature of the inner surface is 19.3 ° C resulting in a relative humidity of 52% at the surface.

Figure 32 temperatures variability in ground slab (without mussel shells) (U-Wert, s.f.)

Figure 33 temperature variation during the day (U-Wert, s.f.)

As it can be seen with the blue line, the temperature inside of the dwelling is going to be constant thanks to the thermal insulation. And I not taking into account the mussel shells.

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Windows in a passive house:

In a window element there are 2 things to consider while is going to be built or installed, one is the frame and the other one is the glazing. The combination of both elements is going to give a values for heat flow of the window (U-value), for only the window (Uw) and for the frame (Uf), which have to be used to determinate if it is a passive house window or not, in order to this it will be accepted or not. The areas of glazing and frame Ag and Af It has to be used also the transmission coefficient between window and construction (Ψinst) transmission coefficient glazing-edge (Ψg). With all this data and also the areas and perimeters of the glazing (Lg) part and frame (Linst) could be determined the total U value and U value installed with the following formulas:

(WBDG, s.f.)

U-Value for the frame and for the window U-value indicates the rate of heat flow due to conduction, convection, and radiation through a window as a result of a temperature difference between the inside and outside. The higher the U-factor the more heat is transferred (lost) through the window in winter. ● ● ●

The units of U-value are: watts/square meters*Kelvin (W/m2K) U-factors for a passive house for a window has to be UW ≤ 0,80 W/m2K A window with a U-factor of 0.6 will lose twice as much heat under the same conditions as one with a U-factor of 0.3.

It is considered many kind of different glazing and frames, which can be found in Passive Houses Institute website, which means that every single one has a certification of passive house component and fulfills the requirements due to build a passive building.

Frames Following the principles that had been establish in the beginning of the projects, all the materials for the frame are going to be ecologic and sustainable, emitting the less CO2 emissions as possible. The aluminum, for example, and all the metals will not be considered as a good material in order to the huge amount of energy required to manufacture them, transport and recycle. As it has been said before, the chemicals are also not welcome to the possible solutions. Finally, after applying this filters, the final results are (obtained from Passive House Institute database).

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Biobased Cassette (Netherlands), Uw = 0.78 W/(m²K) Timber frame of thermal modified timber (λ = 0.095 W/(mK) with insulation core of cork resin (λ = 0.040 W/(mK). Prestressed panels are used for the glazing. Pane thickness: 44 mm (3/18/2/18/3), Rebate depth: 12 mm.

Table. 18 Thermal Data Biobased Cassette (Passive House Institute, s.f.)

Figure 34 Thermal development Biobased Cassette (Passive House Institute, s.f.)

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Figure 35 Biobased Cassette (Tifabos, s.f.)

VÖRDE-Passivhausfenster (North Germany): Uw = 0.78 W/(m²K); Timber-Pu compound frame (0,13 W/(mK), 0,075 W/(mK), 0,040 W/(mK)). Glazing: 4/16/4/16/4.

Pane thickness: 44 mm (4/16/4/16/4), Rebate depth: 20 mm.

Table. 19 Thermal Data VÖRDE-Passivhausfenster (Passive House Institute, s.f.)

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Figure 36 Thermal development (Passive House Institute, s.f.)

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Figure 37 VÖRDE-Passivhausfenster (Fenster Buck, s.f.)

Pfeffer RPS (Germany), Uw = 0.78 W/(m²K); Timber window frame (Spruce/Fir 0,11 W/(mK)). Because of the slim frame, good spacer (SWISSPACER Ultimate) and optimized geometry, this window achieves the standard without additional insulation. Pane thickness: 48 mm (4/18/4/18/4), Rebate depth: 20 mm

Table. 20 Thermal data Pfeffer RPS (Passive House Institute, s.f.)

Fig. 6 Thermal data (Passive House Institute, s.f.)

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Progression (Czech Republic), Uw = 0.78 W/(m²K); Timber frame (Spruce and Thermowood) with insulation (λ = 0,058W/mK). Used Pane: 48 mm (4/18/4/18/4), intersection of the Glass: 18 mm.

Figure 38 Thermal data (Passive House Institute, s.f.)

Figure 39 Thermal development (Passive House Institute, s.f.)

Figure 40 Progression (SLAVONA, s.f.)

As the only consideration to take in account here is the U value for the frame, Uf, because the glazing has not been chosen yet. Taking in consideration what has been mentioned before and after checking the section details, the final choose are the Biobased Cassette and VÖRDE-Passivhausfenster which have the lowest Uf values and in the section is not being appreciated any metal. In details of Pfeffer RPS and Progression some metals can be determined although is not being described.

Glazing To achieve the value of Ug (EN 673) ≤ 0.80 W/(m²K) for a the glazing, it has to be triple glazing and the air inside is Argon or Krypton, both of them are non-toxic materials and only affect to the humans/animals in huge amount of this in the air, although to produce them is another issue to take in account which one is going to be in the project. And following the data from www.chemicool.com, the prices and energy consume of the production are different which means that the energy used to produced them is higher if the cost is also higher.

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Argon: 100g = 0,5€ Krypton: 100g = 31€

The chosen material is going to be Argon, as far as it not decrease the U value of the glazing a lot.

For the glazing it is also important to have a high level of light transmission and an ultimate solar heat gain (g) for thermal insulating windows.

- Iplus Advanced 1.0 T (Belgium) (AGC, s.f.)

Figure 41 Iplus Advanced 1.0T thermal data (Passive House Institute, s.f.)

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ClimaGuard Premium2 (Germany) (Guardian, s.f.)

Figure 42 ClimaGuard Premium2 (Passive House Institute, s.f.)

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SGG PLANITHERM ULTRA N (Germany) (Saint Gobain, s.f.) (glass solutions, s.f.)

Figure 43 SGG Planitherm Ultra N (Passive House Institute, s.f.)

As it can be seen, the measurements and the gas between the glazing are shown in the pictures for every kind of glazing, for example: this means 4 mm of glazing, 18 mm of Argon chamber, 4 mm of glazing, 18 mm of argon chamber and 4 mm of glazing, and the total Ug value is 0,53 PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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W/(m²K). The g value for the gains it is better as huge as possible, as the building is being situated in Denmark the best would be g â&#x2030;Ľ 0,5, so the final election is the 2nd or 3rd glazing.

As conclusion, the total U value for a window is the combined calculation of the values obtained before from the glazing and from the frame. The formulas mentioned before are going to be used for the calculation.

đ?&#x2018;&#x2C6;đ?&#x2018;¤ =

0.53 â&#x2C6;&#x2014; 4.2 + 0.75 â&#x2C6;&#x2014; (0.127 â&#x2C6;&#x2014; 7.7) + 0.027 â&#x2C6;&#x2014; 8.2 = 0.75 đ?&#x2018;&#x160;/đ?&#x2018;&#x161;2 4.2 UW â&#x2030;¤ 0.80 W/m2K, it fulfils the standard.

đ?&#x2018;&#x2C6;đ?&#x2018;¤, đ?&#x2018;&#x2013;đ?&#x2018;&#x203A;đ?&#x2018; đ?&#x2018;Ą =

0.53 â&#x2C6;&#x2014; 4.2 + 0.75 â&#x2C6;&#x2014; (0.127 â&#x2C6;&#x2014; 7.7) â&#x2C6;&#x2014; 0.027 â&#x2C6;&#x2014; 8.2 + 0.027 â&#x2C6;&#x2014; 8.2 = 0.81 đ?&#x2018;&#x160;/đ?&#x2018;&#x161;2 4.2 UW,inst â&#x2030;¤ 0,85 W/m2K, it fulfils also the standard

In this example it can be seen the biggest window that is going to be installed with a Biobased Cassette frame and SGG PLANITHERM ULTRA N glazing.

XX.

Main door

The main door chosen is called Vermaj and is from Czech Republic, the company nameâ&#x20AC;&#x2122;s New Rock. The Uvalues for the door are UD = 0.39 W/ (m²K) and once it is installed is UD, installed = 0.47 W/(m²K) which fulfils the criteria because is less than 0.8 W/(m²K). The door is 1.10 m wide by 2.20 m tall. The same company is doing a door with glazing where the U-value increases until UD = 0.53 W/(m²K) and UD, installed = 0.59 W/(m²K) which is also enough for the Passive House Standard. Doors and frames are made of wood, with 140 - 150 mm of wool with a total thickness of 180mm and a quadruple glazing if it is installed, it has no chemicals, the weight is around 80-100kg and the wood (oak or larch) is local-sourced.

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Figure 44 Picture of the door (New Rock, s.f.)

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Figure 45 Section door

Figure 46 Section door with glass

Foundations

For the foundations we want to skip the concrete as a material itself as much as we can. But, the issues to avoid concrete during the foundation phase are huge. Concrete itself has an extremely good performance for the foundations, supporting the loads, working as an airtight layer, doesnâ&#x20AC;&#x2122;t let the humidity enter inside the building, neither the insects and it is easy to work with. The main problem for us, is that concrete is not natural at all, it needs a huge producing process using many energy and some chemicals. After knowing that it has been decided to try to avoid the concrete for the project.

The problem is, what material it has to be used?

It has been a trouble to find a natural material for the foundation, because they are not tasted and no longer used as the society is using concrete and steel.

The final answer for the house foundation are Mussel Shells â&#x20AC;&#x153;The mussel's external shell is composed of two hinged halves or "valves". The valves are joined together on the outside by a ligament, and are closed when necessary by strong internal muscles. Mussel shells carry out a variety of functions, including support for soft tissues, protection from predators and protection against desiccation.

The shell has three layers. In the pearly mussels there is an inner iridescent layer of nacre (mother-of-pearl) composed of calcium carbonate, which is continuously secreted by the mantle; the prismatic layer, a middle layer of chalky white crystals of calcium carbonate in a protein matrix; and the periostracum, an outer PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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pigmented layer resembling a skin. The periostracum is composed of a protein called conchin, and its function is to protect the prismatic layer from abrasion and dissolution by acids (especially important in freshwater forms where the decay of leaf materials produces acids).” Wikipedia.

Advantages:      

Drainage layer under and buildings.

Insulation and capillary filling material in crawl spaces and basement slab.

Insulation of floors etc.

Drain Material in natural roofs.

Roof covering.

Drain and fill material in drainage and evaporation system.

Fig. 7 Mussel Shells

The mussel shells becomes a wasted material once we eat them and Denmark has a large production, more than 100,000 tons per year, the shell itself is thrown away after the meat is eaten that makes it a reused and natural material. The properties of the Musselshell for the foundations of the buildings have not being tested that much as is not used that often. But, VIA University Collage made a project with few companies for the installation of boreholes in the Brædstrup power plant and had used mussel shells as thermal insulation to try to avoid the temperature difference between outside and the underground and they made some laboratory tests.

Fig. 8 Number of mussel shell production in Denmark per year in tons [Annex 5]

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The factories in Denmark are situated in the following points:

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Lillebælt Vadehavet Kattegat Limfjorden

Fig. 9 Mussel shell factories location (Google Maps, s.f.)

After the pick up the mussel shells have to be processed and cleaned due to reduce the fish odor.

The thermal conductivity of the mussel shells is depending on the crushed level, if the shells are entire, the lambda value is 0.12 W/mK and with 60% crushed, the lambda value is 0.112 W/mK (information from Annex 7) The price is more or less 10 €/m3 delivered only. It means that the price is only for the transportation, the material itself doesn’t have any cost, so the final cost depends on the situation of the building, the distance from the factory, the capacity of the truck and the quantity of Mussels required.

When it is 44kPa, the settlement is only 2mm and for 6 mm settlement the load is 70kPa, it is going to be the reference for this project. But applying a safety coefficient of 1.5, the loads can’t be above 70/1.5= 46.67 kPa. In this project is going to be use a layer of 1000 mm of mussel shells as an insulation and loads distribution to the floor.

XXII. Details In order to define the junctures and constructive details between the materials used in during the project it has been used AutoCAD 2013 and also Therm 7.4, the second one has been used to determine the temperature across the constructive elements, the heat flux through the materials shows where the losses PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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are bigger and it can be corrected if it would be necessary, and check if this materials could have been used to use in the building. The outside temperature for the Therm calculations is -12ยบC and 100% humidity, trying to fulfil the worst possible case in Denmark and 20ยบC inside the dwelling, all the temperatures between 18 and 22ยบC are going to be considered good for the thermal comfort.

Panel-panel south In this case the panels placed in the south faรงade have a connection between them hat can produce losses of heat and temperature and also is going to be checked how are going to fit between them.

Figure 47 Panel-panel detail in the building

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Figure 49 Panel-panel temperatures variation

The temperature inside is going to be >19.3ยบC

Figure 48 Panel-panel heat flux

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Panel-panel no south This panels have a different interior columns because as it has been shown before they have to support less loads.

Figure 50 Panel-panel detail

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Figure 51 Panel-panel temperature variations

Temperature inside: >19.3ยบC

Figure 52 Panel-panel heat flux

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Roof south The roof slab connection is going to be the same for the north faรงade and for the south one, the only changes are the roof itself with the tiles and the columns from the panels coming to the top of the slab, but in this case the south faรงade is the worse situation to analyse the temperature losses and thermal fluxes because the more presence of wood in the columns. The beams of the roof are supported in another beam fixed horizontally to the panels, distributing the loads homogeneously. The red line is an airtight and waterproof membrane to avoid leaks of air in the juncture and also possible water infiltrations. Between the beams and the cork is placed an OSB panel to not let the inside humidity go outside and have a good support for the panels. Outside is installed chipboard in order to let the straw breath for the outside part.

Figure 53 South roof detail

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Figure 54 Temperature flux between the materials

The maximum temperature achieve inside is 19.7ºC, but in general it doesn’t reach that temperature, it stays > 17,4ºC

Figure 55 Heat flux in the roof

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Roof slab ending in east or west façade As it can be see, the detail before and this one are similar, the differences are the continuity of the panel until it reaches the roof and the connection between the roof slab and the panel, because in this case, the beams are parallel to the panels and the connection will be fixed like before but in this case, it can be avoided one beam because it doesn’t need to end in another one as far as it can be fixed itself to the panel. Also now it can be seen the Warmcel insulation between the beams.

Figure 56 Roof detail with AutoCAD

Figure 57 Temperatures in the roof

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The temperature inside is >19.5 in almost all the cases, in the conection point between the slab and the panel the temperature drops down until >17.4ÂşC

Figure 58 Therm heat flux

Foundation-wall south and north In this detail it can be seen the foundation with the mussel shells (1 meter deep) and after a layer of 5 cm of cork where the beams are placed, after the beams there is another layer of cork and OSB avoiding the condensation acting as a waterproof and airtight layer.

The beams are not crossing the panel in order to donâ&#x20AC;&#x2122;t have thermal bridges and a wood beam is placed in order to do not let touch the straw with the ground and distribute the loads into the ground.

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Figure 59 Foundation AutoCAD detail

Figure 60 Temperature flux from Therm

The tempertures in the surface of the materials going inside the dwelling are most of them >19.3ยบC but in some cases is > 17.1ยบC

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Figure 61 Heat flux from Therm

Wall-foundation east and west faรงades In this case the space between the beams is filled with Warmcel, in order to improve the final U value of the ground slab and achieve a better conditions.

Figure 62 Foundation AutoCAD detail

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Figure 63 temperature through the materials

In this case the temperatures are in the most of the parts >19.4ยบC in others is >17.4ยบC

Figure 64 analyzation heat flux

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Window detail For the window detail it can be seen how the plaster is going making the curve and going to the inside part of the wall to keep the airtightness and the insulation, the window frame it doesnâ&#x20AC;&#x2122;t corresponds to the chosen frame because it had been impossible to get the detail from the company. It also can be seen the triple glazed window.

Figure 65 Window detail in AutoCAD

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Figure 66 Temperatures in the materials

In this case the minimum temperatures inside are lower because of the junctures between frames and panels, but when outside the temperature is still -12ยบC the worst temparatures achived inside are around >15.2ยบC, which it means is not bad having -12ยบC outside.

Figure 67 Heat flux

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For the heat flux it can be seen that is higher than any other part of the house and is where it has to be more aware building up the windows and frames because otherwise it can be a huge leak of heat.

XXIII.

Energy part

In this part the reader has to be aware that the house is considered to be linked to public services such as potable fresh water, electricity grid, and sewer system, but not to the district heating. The authors considered that this house can be placed anywhere in Denmark or even in other European countries where district heating does not necessarily exist in majority. Also as the house can be located in the countryside or in a city, where the use of renewable energies such as photovoltaic panels or thermal solar panels do not necessarily worth it because of shadows from other buildings for example. The author assumed that being on grid the house should use the grid system, as the electricity in Denmark will be produced mainly thanks to renewable energies in few years. The reader has to be aware also that the house studied as an example is supposed to facing south with big openings etc, as a consequence if the house is located in dense area with lot of shadows, the windows distribution should be ever different as the house will not necessarily have a lot of solar gains.

The reader can find after this energy part a part where the house studied is totally off-grid with study of photovoltaic panels, thermal solar panels, rainwater harvesting system for potable usage also and â&#x20AC;&#x153;naturalâ&#x20AC;? sewer system.

Different systems to heat the house a. Radiators

Figure 68: Radiator (thermaskirt, s.d.)

A radiator heating system represents an installation of the central heating. In the system, heat is generated in the boiler. Then the heat is distributed by hot water (heat carrier fluid) to the radiators. The radiators release the highest amount of heat to the heated space by convection and one part by heat radiation.

Using radiators means that during the design phase the place where the pipes (go and return pipe) will be installed and so as the radiator itself has to be taken into account. Also nowadays manifold for water pipes are used which means that we have a parallel installation, meaning that one pipe go to one radiator which necessarily means more pipes to be used.

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Figure 69: Manifold installation for pipes going to the radiators (media.xpair, s.d.)

 Advantages :  Great and quick power possible (quick to heat up the rooms)  Choose of temperature depending on the rooms via thermostats  Low temperature radiators 45 inlet/35 outlet/20 room temperature instead of 90/70/20 can be used if low amount of heat loss of the house.  Disadvantages:  Expensive solution (heaters and pipes)  Take some space in the room

b. Floor heating A floor heating system is quite the same as a radiator system but the floor itself is the radiator, the pipes are installed below the top surface of the floor and give radiant heat passing through the material.

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Figure 70: Section of a wood floor heating system (williambeardflooring, s.d.)

 Advantages:  Great power  Choose of temperature depending on the room  No space taken in the room  Good radiant heat =better comfort (the human body feel more comfortable if the warm comes from his feet)  Temperature running around 30 35°c of the room so less energy consume to heat the water.

 Disadvantages:  Relative expensive solution  Takes time to heat up if heavy construction

c. Wall heating A wall heating system is the same principle as floor heating but with the pipes incorporate in the walls.

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Figure 71: Wall heating system showing the layout of the pipes in the wall (spec-net., s.d.)

 Advantages:  Great power  Choose of temperature depending on the room

 Disadvantages:  Relative expensive solution  Walls with integrated heat pipes must be relatively free and not covered  Inserting screws, nails must be done with great accuracy  Little experience with wall heating in Denmark  Could only be used in inner walls with prefabricated straw panels

d. Air heating An air heating system is basically the ventilation system in which circulate hot air (max 52°C to avoid burn dust smell) so the only thing that change compare to a normal ventilation system (a heat recovery system with an efficiency of 75% minimum) is that a device is added in the ventilation unit to heat up the incoming air going to the rooms. Using air heating required to have heat demands lower than 15 kWh/m² year, which is exactly the value that has to be not exceed for a passive house. As you can notice on figure x it is a good idea to make the fresh air transit into a pipe underground in order to enhance the efficiency of the system in case of really cold days.

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Figure 72: Ventilation system of the house showing the heat exchanger and the heat device (Passipedia, s.d.)

 Advantages:  Simple and cheap installation (ventilation system has to be install anyway)  No space taken in the room  Fast reaction of temperature stat or stop  Disadvantages:  Limited power transfer (max 15 kWh/m²)  Same temperature in all spaces (same ventilation flow)  Opening the window in winter should not be exaggerated as it disturbs the heat recovery system.  Need a technical room with good sound insulation

e. Rocket (stove) mass heater A rocket mass heater (system used in the house in Friland in the house made of straw, you can read the interview done by the authors in the annexes) is basically a big mass made of materials that can support high temperature (usually bricks or concrete). Thanks to the fire the heat is transferred to the surroundings material which store this heat and release heat slowly in all the space around. The particularity with this kind of mass heater is that all doors of the house has to be open in order to reach all the rooms. Also you might need to burn wood almost every day during winter time and be present during the process. 1 kilogram of wood can deliver 3.5 kWh of heat and if and if pipes are placed inside the rocket stove (between the first layer and the second layer, where the smoke is circulating) 25% of heat released can be used to heat the water for domestic hot water usage which means 0.25*3.5=0.875 kWh/kg of wood. (Numbers given by Lars Keller from the company Small planet which is an installer or rocket stove located in Friland www.smallplanet.dk )

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Figure 73: Rocket mass heater with wood. Picture from Friland trip in Jens Peter Mølgaard House

Figure 74 Rocket mass heater section showing the principle of heating hanks to the smoke

 Advantages:  Comfort radiant heat  Shape and aesthetic as desired  Can be used to heat the water for domestic hot water usage  Disadvantages:  Take place in the room (1,5 m² minimum)  Heavy construction that has to be taken into account for the foundation system in case of big masonry elements.  System not digitally controllable and presence of people required during the fire process (30 min to 3 hours per day and maximum 1h30 for the house studied)  Long time before getting heat available PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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Can be inadequate with children in the house

f. Choice of heating system (on-grid) After have seen the different devices that can be used to heat up the house, the choice can be made in accordance to the authorsâ&#x20AC;&#x2122; targets which are a low investment price and a high sustainability level but also the system has be suitable for most of the people as the authors wants to make straw houses more popular, which means an easy controllability of the system so as a quick reactivity. The sustainability criteria is link with the embodied energy and CO2 to produce install and maintain the devices and its recyclability. As an example it is stated that a plastic pipe as a really low level of sustainability compare to an iron pipe1 : ( Embodied energy : PVC pipe = 67.50 MJ/kg and 24.40 kg of CO2/kg, Iron pipe = 25 MJ/kg and 1.91 kg of CO2/kg).

To read the table below it is necessary to understand that 1 means a high Investment cost, 2 a medium investment cost and 3 a low investment cost. Then 1 means a low level of sustainability 2 an intermediate level and 3 a high level of sustainability (compare to the others). Also the controllability is taken into account with 1 means a low controllability, 2 intermediate controllability, 3 a high controllability. Finally the reactivity of the system is taken into account with 1 meaning a low reactivity, 2 and intermediate reactivity and 3 a high reactivity. Obviously the more the system has 3 as rate better it is for our choice.

Table 1 : Comparison of heating systems with 4 criteria: investment cost, sustainability level, controllability and reactivity. Self-made table RADIATORS

FLOOR HEATING

WALL HEATING

AIR HEATING

MASONRY STOVE

INVESTMENT

2

1

1

3

2

SUSTAINABILITY

1

1

1

2

3

CONTROLLABILITY

3

3

3

2

1

REACTIVITY

3

1

1

3

1

As it is indicated in the table above the system which has the highest rate in each criteria is the air heating system (apart the sustainability level of the rocket stove which can be made with recycled bricks). It was kind of obvious as there is a low investment price because of the fact that there are no piping or insulation material but only the device to heat up the air in the ventilation unit as the ventilation system has to be installed anyway. Then in terms of sustainability there is only the heat up device that has to be taken into account, unfortunately the authors had not be able to find any data related to the embodied energy and CO2 of this can of device. Nonetheless the authors assumed that it is lower than the sum of all the piping systems that can be used in other systems such as radiators, floor and wall heating.

Different sustainable ways to provide air heating As it is known that air-heating is going to be used in the house, the aim now is to find a sustainable way to supply energy to heat up the air that will be delivered to the rooms. The authors have as target to have a low

1 http://www.greenspec.co.uk/building-design/embodied-energy/ PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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investment price with a high sustainability level for the choice of the needed device. In this part the authors describe different systems that can be used to heat the house by air heating.

a) Compact unit A compact unit looks like a big fridge, but it is actually a ventilation heat recovery system link to a small heat pump linked to the hot water tank. The first aim of a compact unit is to use the heat from the exhaust air (after being passed into the air counter flow heat exchanger) which is around 4째C to 8째C. By using a heat pump it is possible then to heat up the water in the boiler. In order to heat up the supply air to the desired temperature (automatic controlled depending on the outside temperature from 20째C to 41째C available on the market on November 2015) the hot water from the water tank is used thanks to a water to air heat exchanger or water heating element.

Figure 75: Compact unit scheme, composed of a heat recovery system, a small heat pump on the exhaust air heating the boiler that we can use the water from to heat up the supply air to the temperature needed (http://passiv.de, s.d.)

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Figure 76: Compact unit composed of a small heat pump, the heat recovery system and the water tanks below. (nilan.dk, s.d.)

A compact unit can works on different mode depending on the outside temperature and the domestic hot water needs: 1) Passive heat recovery: Only the air counter flow heat exchanger is working, so the temperature outside is hot enough to deliver a needed temperature of 20°C inside and at that time the water tanks has been already heated up. (see figure 77 below) 2) Active heat recovery The air counter flow heat exchanger and the heat pump are working at the same time, there is the need of domestic hot water and maybe also a need of supply air over 20°C as the temperature outside is low.

The heat pump delivers heat to the water tank and the heat from the water tank is used to heat-up the supply air. (see figure 78 below) 3) By pass mode: It is almost the same temperature outside than inside the house and the tank is already heated up for use of domestic hot water, so only ventilation is needed, the fresh air goes directly inside the house and the exhaust air is directly throw outside without using the counter flow air heat exchanger. (see figure 79 below) 4) Hot water mode: The house only need domestic hot water and the temperature outside is high enough to not heat up the supply air, so the heat pump is working and delivers heat to water tank to heat up the water. (see figure 80 below)

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5) Active cooling mode (not all the compact units on the market, none using active cooling is passive house certified): The heat pump is working upside down, the fresh air is cooled and the exhaust air is heated before to be throw outside. (see figure below)

Figure 77: Compact unit in Passive heat recovery mode, only the air heat exchanger is working (nilan.dk, s.d.)

Figure 78: Compact unit in Active heat recovery mode, the heat pump is used to heat up the water tank and maybe also to heat up the air to temperature depending on the outside temperature. (nilan.dk, s.d.)

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Figure 79: Compact unit in bypass mode, the fresh air goes directly to the house and the exhaust air goes directly outside without using the air counter flow heat exchanger (nilan.dk, s.d.)

Figure 80: Compact unit in hot water mode, the heat pump is used to deliver heat to the water tank to heat up the water for domestic hot water usage.

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Figure 81: Compact unit in Active cooling mode, the "hot" fresh air is cooled and goes directly to the house and the exhaust air is heated up and then throw outside.

 Advantages:  Only one unit dealing with ventilation, heating, and domestic hot water  Disadvantages:  Sound level (53 Db for the worst one the market), needs a closed room with high acoustic level insulation.  Using a lot of electricity to run the heat pump all over the year (then depending how the electricity has been produced it can still be sustainable, especially if we consider Denmark situation which has the target to use only renewable energies for electricity by 2050 )  Suitable only with house having low heat loads requirements ( <15 kWh/m².year = passive house) and depending the climate area of the house.

The final choice for the case study is to use the compact unit from Genvex company (Denmark) called Combi 185L certified by the passive house institute (see Annexe A for the certification). This compact unit will allows the house to have air heating, and domestic hot water all year long.

For choosing the compact unit necessary for the house the main issue was the final supply air temperature that it is possible to reach by the unit. Knowing that the house need at least 41°C (PHPP program calculation) to be well heated only by using air heating even during coldest days, the Combi 185L is the only one on the market and certified which is actually able to deliver 41°C. Then the other issue is that using this compact unit the inlet fresh air has to be at least 4°C in order that the unit doesn’t stop for defrosting and start again later on. Which means a lower temperature blowing in the rooms while the defrosting. So there are different ways to pre-heat the inlet fresh air with this kind of unit. One is to use an electric pre-heater (cancelling the certification) and another one is to use an earth tube which catch the heat from the ground during winter which can allow the supply air to reach 4°C or more depending on the length of the pipe and avoid to frost the unit. The unit is suitable to be linked with thermal solar panels to heat the water of in the hot water tank.

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“Frost protection: The anti-freeze protection of this device is implemented externally. The manufacturer recommends the use of an external electric heater for frost protection. However, preheating the air electrically for the heat pump is not admissible, as this additional power consumption is not included in the heat pump’s COP values as stated on the certificate. A ground-coupled heat exchanger must therefore be used, which preheats the intake air to at least 4 °C.” (from Passive house certification see annexe A)

b) Ventilation with passive heat recovery linked to a water heating element It has be demonstrated before that a passive house is able to use a compact unit which delivers ventilation, heat and domestic hot water to the house. But apart a compact unit, one way to provide heating and ventilation at the same time is to use a passive heat recovery system and use the heat from the hot water tank to heat the inlet air of the room until the desired temperature (41°C for the case study) by using a water heating element which is directly installed in the ventilation tube before being blown in the rooms.

Figure 82: Water heating element, taking the heat from the hot water tank to heat to the desired temperature the air before being supply to the rooms. (Nilan dk, s.d.)

The desired temperature which can be delivered depends on two criteria, one is the flow of the air and the other one is the intake temperature from the tank. Taking in account that the air flow of the house will minimum be 154 m3/h and maximum 200 m3/h (in passive house usually we use a 75% required ventilation by the BR 10) and the blowing temperature has to be higher than 41°C. The table below (from NILAN Company) gives the required temperature to intake temperature from the boiler.

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Table 2: Intake temperature needed depending on the airflow and the desired temperature.

The required temperature from the boiler has to be around 70°C to be able to deliver 41°C in the house. This mean that the water has to be at some point of the year especially in the coldest days to be heated until 70°C (because the house will need 41°C of supply air only on the coldest days) which is higher than the usual value which is 60°C. The energy required to heat the water will then also be higher than usual. The (renewable) way to provide this energy to the water tank can be done by an air to water heat pump or a ground to water heat pump both can be associated with thermal solar panels.

The unit chosen for the case study is the Comfort CT 300 from NILAN Company (Denmark) also certified by the passive house institute (see Annexe B). So as the heat exchanger has to avoid to be frozen, the intake fresh air has to be higher than 4.8°C in order the heat recovery system to work properly.

“In order to protect a downstream hydraulic supply air heater, an undershooting of 4.8 °C supply air temperature leads to a shutdown of the unit.” (from passive house certification data sheet, see Annexe B).

As previously a ground-coupled heat exchanger has to be used to reach this minimum temperature. Thanks to the earth tube the house could get cooler air temperature from the fresh air and use the bypass to cool the building during hot days.

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c) Ventilation with active heat recovery linked to a water heating element An active heat recovery means that in addition of the counter flow heat exchanger a heat pump is used to raise the temperature. The heat pump catch the exhaust air after being passed by the counter flow-heat exchanger so as the compact unit but the heat pump is not used to heat the water tank but to heat the fresh air directly, which allow to raise the temperature of the supply air. Only by using the heat pump depending on the desired supply air temperature and the air flow, the device might not be able to raise the temperature as required: Table 3: showing the supply air temperature with an earth tube (heat pipe) and without heat tube, only by using the heat pump (Nilan dk, s.d.)

As it is possible to notice on the graph above, with a flow between 100 m3/h and 200 m3/h without an earth tube (discontinue line=without heat pipe) it can reach on the coldest days (-12°C) a temperature of 13°C to 28°C which is consequently not enough. Assuming that a heat pipe or an earth tube is installed we can reach 26°C to 38°C which is still not enough as 41°C is needed to heat the house. As a consequence it is necessary to add more heat to the supply air before it is blown to the room. The water heating element mentioned before should also be used to raise the temperature until 41°C. The house has an airflow of 154 m3/h, looking at the table above the device is able to deliver around 32°C by itself. So then by using the water heating element it is easy to reach the 41°C. This device is also able to cool the building during the summer time thanks to the reverse mode of the heat pump and so be able to not be over the 10% of overheating as required by the passive house institute.

For the case study the VPL 15 by NILAN Company is chosen. This is not certified by the passive house institute, certainly because of the use of two accessories to reach the desired the temperature. But the authors’ wants to consider different options that could be use in the case study. The graph above is from the data sheet of the VPL 15 (see annexe C)

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In this chapter it has been showed different ways to heat the house only by using air heating. Which one would be the most suitable for the case study house taking in account the level of sustainability and the cheaper investment price? To erect the table below it has been taken in account the different prices of the devices, their certification and functions, and their level of sustainability Concerning the level of sustainability of these devices the authors assumed on their own a level to give as it has not been possible to find relevant data about the embodied energy of them. Nonetheless the level of sustainability have been rank by the amount of input electricity to run them.

Table 4: Comparison between 3 devices for air heating

Compac unit 185L

Comfort CT300

VPL 15

Ventilation, heating, DHW

Ventilation, heating

Ventilation, heating, cooling

55 490 DKK2

33 3903 DKK

39 960 DKK

Sustainability

0.31 Wh/m3 / 0.45Wh (Heat pump running)

0.25 Wh/m3

unknown

Certification

yes

yes

no

Functions Investment Price

Looking at the numbers above it would be the Comfort CT 300 that might be chosen as it has the lowest investment price the highest level of sustainability. But the comfort CT 300 is not able to produce domestic hot water at the same time, it has to be done by another device such as an air to water or ground to water heat pump connected to a boiler which will certainly increase the amount of input electricity to run them both.

To sum up, for the case study the final choice of device to heat the house and at the same time deliver domestic hot water all year long, the compact unit is the one to use.

After the choice of the unit to heat the house and at the same time to heat the building, it is necessary to dimension the air earth tube, which has to be able to deliver a minimum fresh air temperature of 4째C as mentioned before.

Dimensioning the earth tube In this chapter the authors will show what the principle of an earth tube system is. Its components, and the way to install it in the case study.

What is an earth tube system?

An earth tube system is a technical solution allowing to pre-heat or cool the fresh air coming in the accommodation using the ground temperature. It is a shallow geothermal system. The outside air is variable in terms of temperature, humidity depending on the hour the day the season whereas the ground has a temperature which vary slowly compare to the outside air. The aim of using an earth tube is to get fresh air for the heat recovery ventilation system between 4째C and 20째C all year (in Denmark). So in winter time and really cold days the efficiency of the heat recovery system will be enhance as the fresh air will be around 5째C 2 3

Price deliver by nilan compagny with a similar compact unit as genvex combi 185 ex VAT From Nilan compagny ex VAT

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instead of the -10°C outside for example. During summer time the earth tube will supply cool fresh air around 18°C instead of the 25°C of outside air.

This technique was a lot used in Mediterranean countries in order to cool huge buildings during summer time. Obviously they were not using any electricity to run a fan to move the air, all was done thanks to thermodynamics knowledge.

Figure 83: "Wind towers" in Iran allowing to catch the hot dry wind cool it with water and so have a confortable indoor temperature during hot days. (FIabitat, s.d.)

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Figure 84: Iran wind towers technical principle.

An earth tube system nowadays is mostly linked to a heat recovery system as seen in the previous chapter.

These heat recovery system does not have to be frozen which means that around 2°C outside a battery runs by using electricity in order to pre-heat the fresh outside air coming in the heat recovery system to avoid to make it frozen. In the case study, it has been seen in the chapter above, because of the choice of the compact unit COMBI 185 L, that the outlet fresh temperature from the earth tube has to be above 4°C to work without an electric pre-heater.

Taking in account the degree days4 of the city in Billund in Denmark, the outside temperature in Billund is below 4°C for 24% of the year. It means that the earth tube system in our case will avoid to use electric preheater 24% of the year to run the compact unit without disturbances. Also in summer time the earth tube could be used to cool the house, so the authors have decided to count the number of days above 18°C in Billund, not 20°C because the authors have assumed that because of the internal gains (people, equipment of the house…) and solar gains of the house the supply air as to be lower than 18°C to stand with a 20°C inside the house. But in Billund it represents only 4% of the time, nonetheless in this 4% of time the house will be cooled and avoid overheating in the house.

4

http://www.degreedays.net/# giving the temperature difference between inside house temperature (20°C) and the outside air temperature each day of the last three years.

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Graphic 1: Shows the ground temperature depending on the month and on the depth in a borehole made in Horsens (From shallow geothermal system lecture at VIA University College Horsens)

On the graphic above, it is possible to notice that the minimum temperature recorded in the ground in a borehole of Horsens is around 7째C just below the surface (at least 50 cm depth as the temperature above 50 cm depth is quite the same as the air temperature) during the month of March and the maximum would be 18째C during the month of October. This apply in this location only, but shows on average what are the ground temperatures in Denmark. The lowest peak temperature of the ground is in March because the ground temperature is linked to the solar irradiation and the outside temperature, and in Horsens and generally speaking in Denmark there is a few solar irradiation (8am to 4 pm) in winter time so the ground gets colder and colder from October to March, and become warmer and warmer between march and October. So the earth tube temperature could actually get from 7째C to 18째C (in this specific location) without taking the account all the parameters following.

Different parameters has to be taken into account in order to gain as much heat as possible from the ground: 1) The depth of installation of the tube(s), because the deeper you go the higher is the temperature of the ground in winter time and the deeper you go the lower is the temperature during summer time.

2) The distance from the house where is located the house. The closest you are from the house higher is the temperature of the ground.

3) The length of the pipe(s), the longer the tube is the higher is the exchange of heat between the ground and the air inside the tube until a certain limit where it becomes constant as the same temperature as the ground.

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4) The velocity of the air circulating in the tube, the lower is the velocity the higher is the exchange of heat. But to run the fan to circulate the air efficiently in the tube, the air velocity should be higher than 1.5 m/s. and lower than 3.5 m/s to have an optimum exchange of heat between the fresh air and the ground.

5) The ground thermal properties, depending on the materials where the tube is installed the thermal conductivity of the material will be different for example if the tube is buried in clay material you will have a thermal conductivity of 1.3 W/m. k and if you have a loamy soil you will have a thermal conductivity of 2.3 W/m. k. Also the porosity of the material and its water content will also make the ability of the material to exchange more or less heat to the surroundings.

An earth tube system is composed of different components: 1) An inlet fresh air extractor: Which has the role to extract the outside air in the earth tube. It should be placed around 1 m above the ground surface to avoid dust and particles from the ground to come in the tube so as the water which could accumulate on that spot. Obviously it should be placed where the outside air is the less polluted (not close from a road or parking spots, or from the exhaust air of the home). It is composed of filters and small shelters to avoid the pollens, the insects and the rain water to come in. The filters should be cleaned or replace every 2 or 3 years to avoid an over consumption of the fan.

2) The tube in the ground:

Figure 85: Inlet air extractor of an earth tube system (FIabitat, s.d.)

Generally between 30 and 60 meters long for a single family house about 15cm diameter, it can be made of concrete, polyethylene, plastic, or iron. The inside of the tube should be suitable for air to circulate without catching pollutants from the tube material as the air is then used in the house. Also the inside of the tube should be smooth and has a slope of 2% minimum in order to evacuate the condensate of water in the tube whereas the outside of the tube should be ringed in order to increase the soil area in contact with the tube. (That is why the polyethylene PEHD is often used, see the figure).If there are joints and connections along the pipes, those should be as tight as possible to avoid radon5 and water to come in the pipe. The iron tube is the best solution if you can afford as it has a higher thermal conductivity than other types of pipe 3) A trap to collect the condensate water which can be drained by the ground Figure 86: Earth tube made of with some gravels or be able to use a little pump one time of the year to keep PEHD ringed on the outside surface (FIabitat, s.d.) the water level under the tube connection going into the technical room where is placed the heat recovery system.

4) An other tube taking the fresh air directly from the outside air (in order to get warmer air than in the outlet of the earth tube, in order to enhance the heat recovery efficiency) which can be located directly on the outside wall, but for the case study in order to avoid thermal bridge in the straw panel, a second inlet

5

Radioactive substance present in the soil which is harmful for human

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extractor will be installed straight after the trap next to the house connected to the short pipe between the technical room and the trap.

Figure 87: Principal of earth tube system showing the secondary pipe and the trap for the condensate water (FIabitat, s.d.)

After have seen the principle and the components of an earth tube system let’s have a look to its dimensioning for the case study.

To dimension the earth tube the authors used a “demo” version of the software called GAEA6 (produced by the Group for Building Physics & Solar Energy from the department of physics of the University of Siegen in Germany). To be able to dimension the earth pipe some parameters had to be taken into account such as the ground material type, the climate condition (Copenhagen is the only one city available for Denmark in the software), the building volume, the air change rate and so the ventilation flow. The main parameter that is determinant in the case study is the temperature of the outlet air of the tube which has to be more than 4°C. So basically the length of the pipe will be dimensioned because of this need of 4°C 

6 7

Soil parameters: The length of the earth tube will depends on the soil properties. To be in accordance with the project the authors analysed the soil properties at 2 m depth of different locations in Denmark thanks to the “Jupiter”7 tool made by the GEUS (Geological survey of Denmark and Greenland) which is linked to google earth software and allow us to have the borehole profiles everywhere in Denmark.

Link to download the software http://nesa1.uni-siegen.de/index.htm?/produkte_e.htm http://www.geus.dk/UK/data-maps/Pages/default.aspx

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Figure 88: "Jupiter" tool linked to google earth in order to get borehole profile. Here is a screenshot on VIA campus location in Horsens.

At the top of the picture you can notice the different borehole.

Using this tool in random spot around Horsens, Billund, Odense, Copenhagen and next to Friland community (see the borehole profile in Annexe D), it has been shown that around 1m and 2 m depth it was made of sand in all of these locations.

Figure 89: Borehole profile in Energy Pack in VIA campus location, where we can notice that between 0.5 and 5 m depht the soil is composed of sand. (See the complete sheet in the annexe D)

The author then decided to use â&#x20AC;&#x153;sandâ&#x20AC;? as soil in the software and used the defaults data from the software.

It is also important to know where is situated the ground water level (15 m for Via borehole) as the closer is PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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the ground water level from the pipe the higher will be the thermal conductivity of the soil, resulting with a higher outlet fresh air temperature from the earth tube.

Figure 90: Screenshot of GAEA software about the soil properties, choosing "Sand" the software directly give us the Density, Heat capacity, and Thermal conductivity.



Climate: The only climate data available about Denmark on the software was Copenhagen climate



EHX (Earth Xchanger )



o o

Number of Pipes : the author choose 1 as there is no need of more as the project requires a small amount of ventilation rate (154 m3/h) Length of pipes: the author want to profit of the excavation needed to put the mussel shells and decided to put the pipe around the house 1 m from the walls which means a perimeter of 44 meters. But it was not enough to get 4°C on the outlet of the earth tube, as a

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consequence 55m has been chosen. In that way the main inlet extractor will be located 12 m from the house. (see the figure 91) o Pipe diameter: to works well, the velocity of the air in the earth should be between 1.5 m/s (because of the fan efficiency) and 3.5 m/s (because of the air conductivity). Using a website8 entering our ventilation rate (154m3/h) and different sizes of diameter we can get the velocity in m/s. Here are different results for different normative sizes of pipe:  Ø 300 mm > 0.55 m/s = wrong  Ø 250 mm > 0.87 m/s = wrong  Ø 200 mm > 1.36 m/s = almost good  Ø 160 mm > 2.13 m/s = good, min value  Ø 140 mm > 2.78 m/s = good  Ø 125 mm > 3.49 m/s = good , max value So the diameter to choose is 160, 140 or 125 mm the authors have chosen 160 mm in order to get as much heat as possible from the ground and still have a good efficiency for the fan. o Depth of pipe: in order to profit from the excavation (about 1m depth) and to get more heat from the ground and to reduce the cost of too much excavating, the pipes will be placed at 2m depth. o Distance from the building: in order to profit from the excavation for the mussel shells and also because the ground next to the house will be warmer than far away from the house the author choose to place the pipe at 1m from the walls of the building for 44 m and 12 m going far away from the building. o Fan (before or after EHX): the fan is located in heat recovery system.

Results

8

http://www.calculatoredge.com/optical%20engg/air%20flow.htm

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With the input data made before the software gives these results. The important numbers are the minimum outlet air temperature from the earth tube is 4.4°C which secure the compact unit to work well, and also this number secure the calculation as there are 11 m which are not situated at 1m next to the house and the properties of the ground that can be different in reality (a geotechnical survey has to be made on site before) so as the climate data which is the one from Copenhagen which can be different on other spots in Denmark.

The second important number is that the maximum outlet temperature of the earth tube is 17.9°C, which will allow the house to reduce or avoid the overheating during summer time thanks to the earth tube where the inlet could be until 26.5°C. Also the earth tube will be used for 6312 hours per year out of 8760 (365*24) which represents 72 % of the year. The costs should not be taken into account has the values are the defaults values from the software and the authors did not establish a cost estimation of the system.

Figure 91: Drawing showing the earth tube system around the house and the other components.

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What if the house has to respect the building regulation 2015 and 2020?

It has been demonstrated on the chapters above that the house can be heated only by warm air blown by the ventilation system of the house, but this can be achieved only if an earth tube is used (assuming that the authors consider that using an electric pre-heater is not sustainable enough as it doesn’t use the natural resource such as the temperature of the ground) and with the help of expensive solution as the compact unit. Also the fact that an earth tube cannot always be used in all locations, especially in city where single family houses can be attached side by side. This solution of heating by warm air could also be used in city but in the case an earth tube cannot be installed, the fresh –air should be pre heated thanks to an electric device, this could be judge acceptable by some clients as it would be used 24 % of the time during 1 year (corresponding to the number of days in which the outside air is below 4°C in Billund location) and taking in account that the electricity production in Denmark will be more and more sustainable (produced by wind turbines, pv panels, combined heat and power plant, biogas …).

But on the other hand the authors have to follow the government building regulations to be able to build the house. Until this year, every new house build or renovating had to be build following the BR10 (Building PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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regulation of the year 2010), but from now depending on the date the house got the permission to be built, the ways to build it should be done by following the building regulations 2015 and maybe 2020 (which corresponds to additional sheets from the BR 10, see the annexe E).

Following these regulations the authors are not anymore fulfilling some points such as: 

7.2.5.1 (8) Ventilation systems must be carried out with heat recovery with a dry temperature efficiency of at least 75 per cent. Units that provide one dwelling shall be provided with heat recovery with a dry efficiency of at least 85 per cent.

The heat recovery efficiency of the compact unit chosen for using air heating is 76% (without taking in account that the heat pumps heat the air) 

7.2.5.1 (9) Specific energy consumption for ventilation should not exceed 1,500 J / m³. For facilities serving only one dwelling, the limit shall be 800 J / m³.

The house doesn’t fulfil that, as the compact unit consumes 0.31 Wh/m3 = 1116 J/m3 (see table 4 above). Knowing that the compact unit was the only one on the market available and which is able to deliver 41°C as needed to heat the house all year long, the use of the compact unit is no more possible if the authors follow these regulations. 

7.2.5.1 (12) In building class 2020, air heat does not represent the building's only heat source. The requirement does not apply to production halls and the like.

The previous sentence is clear, air heating cannot be the only way to heat the house.

As a conclusion the air-heating solution is no more viable following building regulations 2015 and 2020.

This means that the authors is obliged to introduce radiators, floor heating or wall heating, at least in one room of the house to fulfil the building regulation 2015 and 2020 and to change for a heat recovery system which consumes less than 800J/m3 and with a heat recovery of at least 85 %. Basically the compact unit chosen before is no more suitable as it consumes 0.31wh/m3=1116 J/m3 and has an efficiency of 76%.

In order to fulfil the regulations, the authors has to change the ways the house will be heated-up.

The authors will make the choice then to not use at all the air as a heating system, because it does not exist a compact unit which is able to fulfil the requirements of 2015 and 2020 regulations in terms of efficiency and consumption on the market available and certified by the passive house institute. Finally the authors have chosen to install two small radiators, one in the ground floor which should be placed next to the technical room (scullery) and another one in the bathroom in the first floor in order to have a good airflow from ground floor to first floor and reduce the length of pipe and so the price of the installation of the system. The reader has to be aware that only one small radiator everywhere in the house is sufficient. The heating demand on the coldest day in the house is around 1200 W (PHPP) for the whole house which means around 11.2 W/m². With a low temperature radiator (45 inlet/35 outlet/20 room temperature), one radiator of 0.9m*1.4m is enough for all the house.

a) Choice of the heat recovery system: Following the requirements of building regulations 2015 and 2020, the heat recovery system (without air heating, only passive heat recovery) has to have an efficiency of minimum 85%, and energy consumption less than 800 J/m3 ( 0.22 Wh/m3).

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Looking at the different heat recovery system certified by the passive house institute9, there is none which is able to fulfil all of these requirements. But one is really close to, with a heat recovery of 87 % and an energy consumption of 0.23Wh/m3= 816 J/m3 (see annexe F). Knowing that the air change rate is 0.58 Volume (of the house) per hour which means 0.58 *154 (m3/h) * 24 (hours)= 2143.68 m3/day. Then the consumption of electricity per day is 2143.68*0.23=493 Wh/day so 493*365=179945 Wh/year = 179.9 kWh/year ( 54 €/year or 400 DKK/year) The price of investment of the heat recovery unit (alone) can be between 1500 € and 4000€.

The supply air is not so much so 4000 € (30 000 DKK) can be consider as final cost with the installation of the unit and all the piping system in the house.

Also this unit has to have a frost protection:

Figure 92: Part of certified data sheet of the WS 320 KET, showing that the electric heater for pre-heating the air will start when the temperature outside is less than -6.3°C.

So if the temperature outside is less or equal to -6.3°C the electric heater starts to run. Taking in account that in last three years there were only 3 days where the average temperature was below -6.3 °C (-8.3°C, -8.7°C, -6.9°C ). If the electric heater is used, and if a security scale is added and assume that 5% of the year it would be below -6.3°C which represents around 20 days. Assuming that this temperature is for 24H of the day.

The consumption of the electric heater would be 20 (days) *24 (hours) *1900 (W) =912000 Wh =912 KWh. This represents a lot of energy consumption knowing that the consumption of electricity of the house is around 4000 Kwh/year (PHHP calculations) taking in account that an heat pump (runs with electricity) is used for space heating and DHW. An alternative to this electric pre-heater can be an water heating element (no information on the data sheet with the possibility to use this element or not on the heat recovery system chosen) as seen previously (see figure:15) (the hot water from the tanks is used to pre-heat the fresh air) and it will consume only the pump necessary for that which is usually around 5 W of power which means 20*5*24=2400 Wh =2.4kWh for 20 days below -6.8 °C. To be more realistic if it is assumed that temperatures below -6.3°C occur 3 days a year it would then consume 3*24*1900=136800 Wh =136.8 Kwh (42€ or 310 DKK) which then does not represent a big amount of electricity to be used if the client is on-grid.

So being on-grid and living in Denmark the choose of a heat recovery system with high-performances in order to follow building regulations 2015 and 2020 with an earth tube installed or if not possible an electric preheater or a water heating element which will allow to have an air blown at 16.5 °C minimum all year long is perfectly suitable if it is considered that the electricity used is produced thanks to renewables ways.

After have seen that the use of a compact unit which is able to heat the house is no more possible following building regulations 2015 and 2020, the house need another way to heat the water for the radiators and also for domestic hot water usage. What are the different ways to achieve that?

b) Which renewable way to provide heating and DHW 

9

Air to water heat pump

http://www.passiv.de/komponentendatenbank/kleine_lueftung/

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An air to water heat pump is a heat pump catching the air from outside which make a refrigerant liquid to be hotter and deliver this heat into the hot water tank of the house to heat up the water for the radiators and domestic usage. It means that there is a unit outside of the house and another unit inside the house (usually combined with the hot water tank). A heat pump can be classified as renewable source, as the heat pumps use 75% of the outside air and 25% of electricity to release 100% of heat to the house. In other words to deliver4 kW of heat to the house you catch 3 kW (naturally) from the outside air and use 1 kW of electricity to run the heat pump. This is called the COP (Coefficient of Performance) of the heat pump. A heat pump is suitable for well insulated houses or building, otherwise the electric consumption would be really high, also the heat pump has to be carefully sized in accordance to the building heat losses and DHW needs.

The COP in the case of an air to water heat pump will vary directly because of the outside temperature.

Usually during really cold days (-12°C) the COP is around 1.5 and during hot days the cop can reach 5.

The reader has to be aware that the dealers usually give a COP with an outside temperature of +7°C and a hot water at 35°C which is not relevant enough to make accurate calculations. As it is practically impossible to get real value of COP depending on the outside temperature and the hot water temperature the authors will make assumptions to make the calculations.

In the house the boiler has to be heated up at least at 60°C few minutes a day for hygienic reasons, even if the radiators can work with 45°C. The needs of the house are 1.2 kW for the heating and 4 kW for DHW so a total of 5.2 kW.

Figure 93: Danfoss data sheet about an air to water heat pump.

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On the screenshot above you can see a data-sheet from DANFOSS company, this shows the technical information of an heat pump able to deliver 6 kW of power which is suitable with our 5.2 kW of needs.

The COP with an outdoor temperature of 7°C, heating the water at 35°C is equal to 4.7. This means that in theory if I need 5.2 kW power of heat I would need to deliver to the heat pump 5.2/4.7=1.1 kW of electricity.

As there is no data about the COP values depending on our parameters deliver by the company which are in the worst case -12°C outside and a hot water at a temperature 60°C. The author will than assume a COP of 1.5°C with this parameters, and with 20°C the COP will be equal to 5. The COP is then calculated thanks to a coefficient line. So when it is 0° outside for example the COP will be equal to 2.81.

In order to have an overview of the electric consumption of the heat pump on 1 year this table has been erected: Table 5: Shows the COP Values depending on the months and the final electricity consumption to rum the heat pump with temperature of year 2014 in Billund

jan average air temp COP heat kwh DWH kwh total = electric cosumption kwh

feb 2,2 3,0498 345 189 534 175,09

mar 3,03 3,14027 174 189 363 115,60

apr 4,13 3,26017 113 189 302 92,63

may 6,83 3,55447 9 189 198 55,70

jun 9,03 3,79427 0 189 189 49,81

jul 12,47 4,16923 0 189 189 45,33

aug 14,93 4,43737 0 189 189 42,59

sep 16,7 4,6303 0 189 189 40,82

oct 12,57 4,18013 0 189 189 45,21

nov 9 3,791 6 189 195 51,44

dec 7,47 3,62423 144 189 333 91,88

total year 2,5 3,0825 355 189 544 176,48

3414 982,59

The yearly consumption of electricity is then around 983 kWh/year. = 299 €/year (0.304€/kwh in Denamrk10) Table 6: Shows the COP values depending on each months but in this case -10°C outside are considered to be the average temperature of January and December. The final electric consumption is hown also jan average air temp COP heat kwh DWH kwh total = electric cosumption kwh

feb -10 1,72 345 189 534 310,47

mar 3,03 3,14027 174 189 363 115,60

apr 4,13 3,26017 113 189 302 92,63

may 6,83 3,55447 9 189 198 55,70

jun 9,03 3,79427 0 189 189 49,81

jul 12,47 4,16923 0 189 189 45,33

aug 14,93 4,43737 0 189 189 42,59

sep 16,7 4,6303 0 189 189 40,82

oct 12,57 4,18013 0 189 189 45,21

nov 9 3,791 6 189 195 51,44

dec 7,47 3,62423 144 189 333 91,88

total year -10 1,72 355 189 544 316,28

3414 1257,77

The yearly consumption of electricity then become around 1257.77 kWh/year.= 382 €/year If the 983 kWh/year are considered compare to the whole electricity consumption of the house which is around 4000 kwh/year it represents about 983/4000*100= 25% of the whole consumption electricity.

The price to install a heat pump with danfoos company (with a integrated tank) is between 7000€ and 10000€, as the house needs are low we would get the smaller heat pump to install so 7000€ (52 000 DKK) could be considered as the final price investment.

As a conclusion an air to water heat-pump to heat the house and deliver DHW all year long is suitable for a house which is on-grid. Because the 316.28 kWh needs in December month could be achieve with difficulty by PV panels because it means that it should be placed around 135m² of PV panels (less sun in winter time and more heat needed). That means a huge investment just to be able to deliver enough electricity to the heat pumps and other appliances in this month, this is not economically interesting at 10

http://ec.europa.eu/eurostat/statistics-explained/index.php/Energy_price_statistics

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all. Even if thermal solar panels are considered to be install to “help” the heat pump it would means to have around 20m2 of thermal solar panels to satisfy only the DWH needs in cold months (189 kWh) which is also not economically interesting.

An air to water heat pump can be considered sustainable if the electricity to run the heat pump has been produced thanks to renewable ways. In Denmark it would be a good choice for a house located in city with no garden as there is only the need to install the outdoor unit which has a size of 0.5*1.2*0.8 m or if the client cannot afford the price of ground works to install a ground to water heat pump. In France it would not be sustainable anymore has 75% of the electricity is produced thanks to nuclear. 

Ground to water heat pump

A ground to water heat pump is a heat pump using the ground as a heat source. This means that there is a heat carrier fluid usually water with antifreeze flowing in pipes who are buried in the ground, and then this heat carrier fluid make the refrigerant liquid of the heat pump to be warmed up and deliver this heat to the hot water tank in the house. It exists different types of way to use a ground source heat pump. The main type used is when the pipes can be placed horizontally at 1 to 2 m (meaning a large surface area) and vertically in boreholes.

On the figure above you can notice that there is many different ways to use the ground as an heat exchanger, one is said to be closed loop system where the heat carrier fluid (flowing in the pipes) is never in direct contact with the ground which can be energy piles (pipes placed in concrete foundation piles) , a pond loop (using the heat from water in a lake next to the house for example), and then the two others that are mainly used, the horizontally way called ground loops (agreements with authorities because of flora and fauna issues) and the vertical way called closed loop boreholes. Apart from that, the open loop system (related to extraction and recharge well) take benefits from the ground water PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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source flowing in the ground (need special conditions an agreement with the authorities as the ground source water can be used for drinking possibility).

The house depending on the location could use all of these systems except the energy piles as concrete foundations are not necessary for a straw wooden house. But the most commonly used are the ground loop and the boreholes for single family house (lowest prices of investment).

1) Ground loop heat exchanger criteria (from Shallow Geothermal System lecture): - need a large space of excavation (at least 1m depth for frozen level) (high price for excavation works) to install the pipes around 2 times the foot print for normal house. It could be reduce for our house to 1.5 as it is passive house and the heat loads are not as high as for normal houses.

- The pipes have to be install with around 0.5m space between each pipes. In order that the heat exchange does not interfere between each pipes 2) Borehole heat exchanger criteria: - need a small surface to be install 10 m² is enough depending on the numbers of boreholes to be install.

- The borehole should not exceed 120m (usually the depth where it is harder to drill in) - Between each boreholes it should be a space of at least 5 m. In order that the heat exchange does not interfere between each borehole.

- It requires deep geotechnical analyses as some issues could occur during the process of drilling. If there is water source under pressure all the water will come to the surface quickly for example.

The authors don’t have any knowledge about the ways to dimension ground loop systems but a borehole heat exchanger will be study thanks to the Earth Energy Designer software used in Shallow geothermal lectures.

The advantage with a borehole heat exchanger is that the ground temperature is stable all year long after 15 m depth which means a stable COP value for the heat pump.

First the ground properties are necessary. The authors have chosen to use the borehole drilled in Energy Park in VIA of 100 depth (see annexe D) to use its ground properties. (Each location has its own ground properties here is just an example). In this borehole there are two main type of ground from 0m to 25 m (25%) there is sand, and from 25m to 100m (75%) there is clay (LER in Danish). There is no ground water level appearing in the borehole so the materials can be considered as dry from top to bottom. The sand thermal conductivity to use is then 1 W/(m.k) and the clay is 0.5 W/(m.k). Taking in account the percentages of these materials in the borehole, the final thermal conductivity of the ground around the borehole is (0.25*1+0.75*0.5)=0.625 W/m.k.

After that other parameters have be enter in the programs such as: o

o

o

The type of filling material between the ground surface and the pipes (usually a 10% mix of bentonite with the ground removed by the drill. in Denmark which has a high thermal conductivity and not harmful for the environment The month heat loads in kWh (calculated by PHPP excel sheet) and the COP of the heat pump (3 chosen even if 4.2 from Danfoos company for the reason that Danfoss consider a hot water of 35°C and not 60°C) The peak loads in kW (corresponding to the size of the heat pump 6KW for the house)

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o o

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The number of hours the heat pump will run each day depending on the month (6hours in winter for heating and domestic hot water needs and 2 hours in summer for domestic hot water needs) The type of heat carrier fluid running in the pipe which has to not be frozen (water and 25% of ethanol most used and less harmful for the environment) The borehole diameter (generally 150 mm in Denmark)

With all these parameters (and others which might not be relevant for the reader) the software is able to give the required length of the borehole to deliver enough heat for the heat pump to run without disturbances depending on the heat and DHW needs.

The software requires only one borehole of 50 m depth, which is surprising not a lot compare to a not passive house which would requires at least 2 boreholes of the same length, as the length is directly linked to the heat loads.

What is the price to run the heat pump?

Table 7: Table showing the heat pump electricity consumption per month depending on the needs of heating and DHW of the house. jan running hours/day numbers o days total number of hours COP kwh delivered electric consumption kwh

fev march apr may june jul aug sep oct nov dec total kwh 2,97 2,02 1,68 1,11 1,06 1,06 1,06 1,06 1,06 1,09 1,86 3,03 31 29 31 30 31 30 31 30 31 30 31 30 92,14 58,64 52,18 33,17 32,72 31,67 32,72 31,67 32,72 32,67 57,52 90,83 3,5 3,5 3,5 3,5 3,5 3,5 3,5 3,5 3,5 3,5 3,5 3,5 535 364 303 199 190 190 190 190 190 196 334 545 3426 152,86 104,00 86,57 56,86 54,29 54,29 54,29 54,29 54,29 56,00 95,43 155,71 978,86 297,57 € 2213,94 DKK

On the table above, the highest consumption during the year is around 156 kWh which is only 11.6% less than the highest consumption (in realistic calculation) using an air to water heat pump. Also the yearly consumption is almost the same as for the air to water heat pump, 982.9 kWh/year and with the geothermal heat pump is around 979 kWh/year. The running cost are also almost the same 299€ and 297 €. So then maybe the investment cost can elect one as the best option?

First, as the geothermal heat pump does not need and outside unit the price of the unit will be around 4000 € ( 30 000 DKK) and about the drilling work there is no define price but a website11 says that it’s between 80€/m and 140€/m depending on the geology. In the case study it is sand and clay, which are soft materials for drilling. As a consequence 100€ could be assumed as an average price. Knowing that the borehole has to be 50 m depths it would cost around 5000€ (only for the borehole). The total investment then would be 9000€ for a ground source heat pump and 7000€ for an air source heat pump.

Following this study it can be assume that an air to water heat pump is the best choice in our case. But the reader have to be aware that the authors are not specialists of heat pumps. Depending on the location of the house, the ground properties and the climate condition can have a big influence with the final choice of an air to water or ground to water heat pump (with borehole in that case) to install.

11

http://www.synergyboreholes.co.uk/water_boreholes/index/cost/

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Also if the owner of the house has no possibility to make borehole in his garden or because there is no access for the driller truck to work in good conditions, or even because of issues with the authorities to make a borehole in the specific location the air to water heat pump can be used.

After have seen the different ways to heat the house by different devices let's make a comparison between each of them.

Table 8: Table of comparison between different heating and ventilation system in terms of prices. (done by the authors)

Air heating +DHW

Ventilation + air to water Heat Pump

Ventilation + geothermal heat pump

Respect BR 2015 2020

No

Yes

yes

All locations

Yes

Yes

no

Investment price

55 490 DKK

81 840 DKK

96 720 DKK

Running cost /year

unknown

2620 DKK / (3000 2620 DKK / (3000 without earth tube) without earth tube)

To sum up this energy section of the house being on grid, theses statement can be verify: o

o o

XXIV.

Respecting only BR 10 the client should choose a compact unit, and ask for a real expertise of the year consumption of the compact unit to see if it is worth it or not. Because it seems like when it is about renewable energies the dealers donâ&#x20AC;&#x2122;t want to deliver the real electric consumption, they just give us an average which does not take into account all the parameters of the house.

Respecting BR 2015 and 2020 should choose a heat recovery system and an air to water heat pump or an geothermal heat pump for heating and DHW purposes If the client has enough space outside of his house to install geothermal heat-exchanger (vertical or horizontal) he should ask an expert to see if it is the best option compare to an air to water heat pump. Cause its ground properties can be really advantageous.

What if the client wants to be off-grid?

In this chapter the authors will show how it is possible to live in the house studied being off-grid in Denmark.

What means to be off-grid?

Being off-grid means that the house is not connected to any public services such as fresh potable water, electricity grid, sewer system, or district heating. As a consequence some devices has to be install in order that the house can run on its own thanks to natural resources.

Also the reader has to be aware that an off-grid house involve a change of behaviour of the client. The client might take some more efforts than only push or turn a button to get heat for example. He should not use systems than have a high electric consumptions such as a dryer machine or dishwashing machine or an heat pump.

What are the devices to use in order to be off grid?

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Heating : The use of any electrical devices with high consumptions (like an air to water heat pump or ground to water heat pump) to heat the house should not be used. The quantity of electricity will depends totally on the photovoltaic panels’ production and also maybe on the wind turbine production. As a consequence the owner should use a wood stove, or a rocket mass stove to heat the house.



Domestic hot water: The same as for the heating, hot water needs should not be covered by electrical devices. During winter the domestic hot water would be deliver thanks to the stove, because we can use the heat from the stove to heat the water. During summer time (when there is no need of heating the house) the thermal solar panels will deliver the domestic hot water.



Ventilation: The ventilation system should be done with obligation by an earth tube as it has been seen before, but the pipe should be buried deeper and be longer. In that way we could get a minimum fresh air temperature of 7°C (if we the house is located in Horsens for example). The use of heat recovery system can also be considered as it consumes only 493 Wh/day. To not use a heat recovery system involve to burn more wood to heat the house.



Potable water: Using a rainwater harvesting system combined with a water treatment unit can supply the water needs of the house. The water tank should be buried in order to not have direct sunlight and too much temperature changes.



Sewer system : First to understand the reader has to be aware that two technics can be used: 1) The grey water (coming from shower, sinks which involve use of natural soaps) can actually permit to grow plants placed in the greenhouse on the south part of the house, these plants actually needs the “bad” part of the water to grow and at the same time they make the water more clean. This more clean water is then pump during the flush time to the toilet for the flushing system. The dark water coming from the toilets is then going to an outside buried tank which is split in two parts, a solid part and a water flowing part going to plants outside which naturally treat this water flowing in the ground. In the solid part some bacteria’s growth and destroy the solid parts by the time and then the water goes to the plants. (it is the same principal as the compost).

2) Here dry toilets are used (no need of water) which means that the owner will have to remove the “box” every weeks for example and then mix it with the compost. (By the time bacteria’s will transform this compost in nutritive ingredients for the soil and can then spread for the soil of the plants).

All these principles comes from the way works an Earthship created by Michael Reynolds.

If the reader wants to have more details about these principles he should look to that video: https://www.youtube.com/watch?v=qlijB6G392Q#t=859

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A kind of earthship has been built in VIA energy park in Horsens by the group of students called “Building tomorrow” (http://buildingtomorrow.dk/)

Dimensioning the stove to deliver heat and DHW during winter As mentioned before, the way to heat the house has to not use electricity, otherwise the consumption would be too high during winter time and the photovoltaic panels would not be able to deliver enough electricity.

As a consequence the easiest way is to use a wood stove/rocket stove to heat the house and to produce domestic hot water during winter months. It means that the owner of the house will have to put wood every day in the stove.

But there is an issue by using a stove in a passive house, the airtightness of the building does not allow any additional oxygen to enter in the house in order that the wood can burn properly. As a consequence a tube from outside should be install in order to deliver fresh air full of oxygen for the wood to burn properly. Also thanks to the warm of the smoke we can install pipes with water running inside around the smoke tube (140°C to 180 °C or between the two layers of the rocket stove in order to get domestic hot water at the same time. Lars from Friland (who make rocket stove in Denmark) told the authors that 25% of the energy of stove can be used for heating water and that 1kg of wood burning can deliver 3kW/h of energy A stove has a capacity from 2kW to 8 kW for single family house depending on the size of the stove and the amount of wood burning.

The heat loads of the house is 1.2 kW and it will be consider 25l/person/day for hot water needs. Assuming 4 people living in the house, the hot water tank should be about 100 L capacity.

During the cold days the heating should work 24hours so the amount of energy will be 24*1.2=28.8 kWh/day to be delivered to the house.

If the stove have a power of 4kW, the time of burning wood per day will be 28.8/4 =7.2 hours If the stove has a power of 8kW, the time of burning wood per day will be 28.8/8 =3.6 hours. The quantities of wood to be burned per day then will be 28.8/3=9.6 kilogram.

In order to have an average of constant temperature the stove should be used at least twice a day, in the morning and in the evening. So if 8kW stove is used the stove should run 1.5 hours in the morning and 2.1 hours in the evening for example.

Is that time enough to warm up enough water for domestic hot water usage? Knowing that 25% ot the stove capacity can be used for heating the water.

Following this formula: With:

P the power capacity needed to heat the water M the mass of the water to be heated up (100L=100 kg) Cp the calorific capacity of the water in J/kg/°C (Cp=4185 j/kg/°C) ∆ T the temperature difference of the cold and hot water (10°C and 60°C so ∆ T =50°C)

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∆ t the time used to heat all the water in seconds (1h=3600 seconds) If the water heat up in 1H the P=5.81 W, for 2H the P=2.91 W and for 3H the P=1.94 W. IF a stove of a capacity of 8kW is used then the power capacity for heating water will be 0.25*8= 2 kW. This means that to have all the water heated from 10°C to 60°C a bit less than 3 hours will be required.

Knowing that to deliver enough heat to the house 3.6 hours is necessary all the water will be heated.

But what happen when the outside temperature are warmer and the stove does not need to run 3.6 hours but only 1hour? The water might not be heated until 60°C then? But if the temperatures are warmer it’s because there is more sun also during the day, so if thermal solar collector are linked to the water tanks, the solar collectors can act as a backup source to heat the water.

Dimensioning the thermal solar panels for DHW in summer time.

Graphic 2: Graph showing the percentage of DHW needs covered by 8m² of evacuated tube collectors depending of the month. The black line represent the DHW needs and if the light blue rectangle reach the black line it means that 100 % of the needs are covered.(From PHPP excel sheet calculation)

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Graphic 3: Graph showing the heating demands of each month. The heating period is from November to March (From PHPP excel sheet calculation)

On the graphics above the relation between heating demands and DHW needs covered by the solar collectors are equivalent (8m²). In summer time when there is no need of heating (April to September) the DHW are covered at 100 % by the solar collectors. And during winter months (November to march) the ratio between heating demands and DHW covered by solar is almost proportional.

On the Silicon solar webstite12 1.1 m² of evacuated solar collector cost 567 € so installing 8 of them will be about 567*8=4536 € taking in account the installation cost it would be 5000€ (37 200 DKK).

As a conclusion of these 2 last parts, it is state that electricity is not necessarily needed (expect the pump for the water to go to solar collectors) to heat the house during winter time and get DHW all year long.

Dimensioning photovoltaic panels Being off-grid does not mean to be able to get some electricity. Using photovoltaic panels and devices with low consumption it is possible to be self-sufficient in electricity.

What are the different components of a off-grid solar kit13?

1) Pv panels 2) Charge controller : A solar charge controller is a device which is placed between a solar panel and a battery.

It regulates the voltage and current coming from your solar panels. It is used to maintain the proper charging voltage on the batteries. As the input voltage from the solar panel rises, the charge controller regulates the charge to the batteries preventing any over charging.

3) Inverter : Solar panels (PV) receive the sun’s rays and convert them into electricity called direct current (DC). DC is then converted into alternating current (AC) through a device called an Inverter. AC electricity flows through every outlet of your home, powering the appliances.

12 13

http://www.siliconsolar.com/30-evacuated-tube-collector-v1-p-503474.html http://waldenlabs.com/diy-off-grid-solar-system/

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4) battery

Figure 94 : Layout of an off-grid solar panels connections between the components (waldenlabs, s.d.)

The first step to dimension the amount of m² needed to get enough electricity is to know the daily consumption in electricity of the house: These are the elements that the authors considered to be enough to live with an â&#x20AC;&#x153;off-grid comfort and their consumption in kWh/day.

Table 9: Electric consumption in kWh/day of appliances use in the off-grid house. (done by the authors)

Appliances

Cosumption in kWh /day

Fridge and freezer

1

LED lighting (20 lights)

0.1

Heat recovery ventilation system

0.5

Pump for toilet flushing

0.05

Pump for thermal solar panels

0.12

Clothes washing machine

1.1

Cooking (gas could be used also)

0.75

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Other appliances (TV, computer, wifi…)

0.2

Total

3.82 KW/day

The authors consider that during winter, the fridge is not necessary need to be used as it is cold enough outside to keep cool the food. And also the authors consider that there is no need to keep frozen food. The same as for the clothes washing machine, the clothes could be wash by hands during winter time. Because it’s during winter that the PV panels receive less sun energy and so produce less electricity. Anyway the authors will consider two cases one with 3.82 kWh/day and other of 1.72 kWh /day.

The different parameters to dimension the surface of solar panels are: 1) the roof slope which is 25° for the house (38 ° being the best slope in Denmark) 2) The location (the authors will consider Horsens in this case) 3) The kind of solar panels Monocrystalline with 14% to 18% efficiency but high embodied energy and expensive Polycrystalline with 11% to 15% efficiency with medium embodied energy and less expensive Amorphe silicium or flexible panels with 7% to 9% lower embodied energy less expensive The authors will make the choice to use Polycrystalline panels as it is the best comprise between the investment price, efficiency and embodied energy.

Using this website http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php it is possible to see what is the kWp to install to get reach the electricity demands of the house. The kWp is the sum of the maximum power output of each panels.

Entering 3 kWp in the program the amount of electricity is given:

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As it is possible to see on the table above, the lower production is 1.74 kWh/day in December and the needs are 1.72 kW/day.

In order to get 3.82 kWh/day the kwp needed is 6.6 kwp so more than twice needed without fridge clothes washing machine.

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A Danish company called dansksolcelle14 located in Aalborg is able to install an off-grid system of 3kwp polycrystalline PV panels for a price of 58,506.45 included the inverter and the batteries. The panels are 250 Wp each which means 3/0.250=12 panels to be installed. Each panels surface is 1.65 m* 0.992m =1.64m²/panel. The total surface area for 3kwp installation is then 12*1.64=19.65 m² (see data sheet on annexe G) For the 6.6 kWp installation the authors will consider the double of this installation in term of price so 117 012.9 DKK and so the number of panels will be equal to 6.6/0.250 = 26.4 so 27 panels which means PV surface area of 27*1.64=44.3 m² The reader has to be aware that during summer months there will be an extra production of electricity compare to the needs, and to not destroy the batteries the electricity should then be used. This extra production could deliver houses in the neighbourhood or use for charging electric cars or electric bikes and if not possible the installation should be shut down when needed.

Let’s calculate a payback period for each installation. The total consumptions (needed) will be consider to be 1.72*365= 635.1 kWh /year and 3.2*365=1168 kWh/year. The price is 0.304€/kwh so the payback periods are:  

3 kwp (without changing the batteries and maintenance) payback period = 41 years 6.6 Kwp (without changing the batteries and maintenance) payback period = 45 years

It is obvious then than being completely off grid the payback period is really not interesting for the moment.

If later some batteries that can handle seasonal charge and discharge then it would maybe become interesting. But about a single family house from now, the best is still to be on grid for economic reasons.

Unless it is the choice of the client to not depends on public energy.

The good thing will be then to sell the over production to the public grid. But it seems that the price that you receive for selling over production becomes less and less over the years: “PV system owners would get the full price – 2.20 DKK – for all electricity used within an hour of being produced. For electricity exported the grid, PV system owners would receive 1.30 DKK [22¢] per kWh in 2013.

To account for falling PV module prices, this rate would fall to 1.17 DKK [20¢] in 2014 and about 1.00 DKK [17¢] in 2015. After 10 years, the rate would be down to about 0.60 DKK [10¢] per kWh.” ( from : http://www.forbes.com/sites/justingerdes/2012/11/30/denmark-moves-to-cool-its-red-hot-solar-energymarket/) So if the over production/ year is considered in both case 3 kwp has an over production of 2940-635.1=2304,9 kWh/ year 6.6 kwp has an over production of 6470-1168= 5302 kwh / year Taking in account that the owner will receive 0.60 DKK/kwh the payback period (without taking in account the increase price of electricity) of the systems will be:  

14

22 years for the 3kwp installation 22 year for the 6kWp installation also.

http://dansksolcelle.dk/produkt/4463/3-kwp-hybrid-anlaeg-inkl.-montering

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The payback period becomes a bit more interesting if the client is on-grid and receive 0.60 DKK per kWh of over production. But the maintenance of the system have not be taken into account, it might increase the payback period.

Rainwater harvesting system Being off grid, the house won’t be supply in potable water from public services. As a consequence the client will have to use a water treatment system which can deliver potable water from rainwater harvesting. In Denmark it is raining a lot, so there might not be any problem about the quantity of water to collect compare to the use.

What are the issues for dimensioning?

1) Roof surface quality for rain water harvesting (no pollutants) 2) Put net on gutters, to prevent leaves and debris to block the gutter.

3) Install a flush diverter before the tank. When it begins to rain for few minutes the first waters touching the roof will “flush” the roof surface, so the water will be a bit dirty and has to go somewhere else than in the tank 4) Install a diverter from the tank, which will allow the tank to not be fully charged in case of big storm for example 5) Install a pump to bring the water into the house with a first filter, until the treatment unit.

6) In the treatment unit the water will go through different filters with smaller and smaller sizes until 5 microns.

5) After the filters, the water pass trough an UV sterilizer (Uv light) that will permit to have a potable water, the UV light can be effective only if filters than 10 or less microns have been used before, otherwise the water might not be potable.

The price of the treatment unit is usually around 900 €15 and as the filters has be changed every year there is about 100€ of maintenance cost/year.

15

http://www.rainharvest.com/rainflo-rainwater-purification-package-32-gpm.asp

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XXV.

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Velux Daylight Visualizer

For the daylight factor for the building it has been used the Velux Daylight Visualizer in order to know how the light from outside influences in the interior of the house. [BR10: 6.5.2 (1)] The Danish building regulation establish a minimum values for the daylight factor and the illuminance as a requirements for the interior of the building. Is applied only for public and working places The illuminance is the total amount of light coming from the sun or other point of light that lands on a surface or object. Is measured in Lux and for a normal building in Denmark it has to be around 200 Lux in order to have a good quality of the light in the dwelling, values close to this amount are going to be accepted as far as it is only for public buildings or working placements.

The daylight factor will be also analysed and studied because in Denmark the total amount of daylight has to be as minimum of 2% in the workplaces. If this 2% is not fulfilled the areas of the windows will be increased but taking in account that the total energy demand will increase and also the overheating if the windows are bigger, but if the value obtained is close to the demands for a public or workplace is going to be accepted.

Specific renders can be seen in Annex 10.

Ground floor

Figure 95 Daylight factor for the ground floor

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Figure 96 illuminance during December in the ground floor (worst case)

Figure 97 illuminance during June in the ground floor (best case)

First floor

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Figure 98 Daylight factor for the first floor

Figure 99 illuminance during December in the first floor (worst case)

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Figure 100 illuminance during June in the first floor (best case)

XXVI.

Conclusions

The first conclusion is the difficulties to know the real characteristics of the materials and basically the straw and mussel shells, both of them are not popular to build with and the information is variable depending on the website or book. For the other materials studied we can say that is not easy to find natural materials without chemicals and toxic components or with a huge amount of energy consumed producing them, may we as a society are building without caring about nature and natural materials that are as good or better than an artificial materials. We are missing the natural sense of the things and going deeply to the plastic ones because they seem better or the industry want you to see them better. As a personal conclusion, we are complicating our lives when we are building a house, and it is simpler than it looks.

The house has fulfilled the Passive House requirements, the calculations can be seen on annexes â&#x20AC;&#x201C; PHPP 1 verification sheet.

One of the big challenges of this project was to make a structure that could take all the loads efficiently and at the same time meet the architectural design and energy design, which has been done successfully. All the structure fulfils the Eurocodes, Danish National annexes and regulations for safety.

Concerning the energy point of view, we have seen that because of the fact that it is a passive house, it allows us to use renewables energies such as heat pumps, and reduce a lot the consumption of final energy of the house. We have tried to use ways in order to have a house being off-grid, unfortunately we have seen that because of the fact that we are used to have a constant flow of electricity since we are born, we have difficulties to adapt to what the nature gives us. And until now there are no technologies than can be used in a single family house to store energy for seasonal periods. Otherwise if we would not using so much electricity and use the techniques that was used before the industrial revolution we would be able to live off PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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grid. At the same time the human should more trust the nature and what it can offer and not what the industrial companies want us to buy.

About the cost we have figured out that we could not compare accurately with usual ways to build as these kind of techniques and the use of natural materials have been supplemented by the industrial revolution.

But the use of natural resources means less embodied energy which means less fossil resources to extract and so less money for the companies. But the people in the world begins step by step to realize how the nature can guide us to a better future.

As a final conclusion, we missed the experience to work with such materials in this project and we had to find it. We had been talking with many experts about straw, plasters and mussel shells basically, and the main reason is because we figured out that the websites are important but the experience of the people working with a specific materials is better.

If we would like to develop the project itself, for sure we would need an expert with us as a guide because of this rare materials used for the construction.

XXVII.

Annexes

Structural Calculations 1st floor slab beams calculation Following loads acting on each beam: -Self weight: đ?&#x2018;&#x201D; = 1,28 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 -Imposed load16: đ?&#x2018;&#x17E; = 2 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 Ultimate limit state combination: 1,0 â&#x2C6;&#x2014; đ??žđ??šđ??ź â&#x2C6;&#x2014; đ?&#x2018;&#x201D; + 1,5 â&#x2C6;&#x2014; đ??žđ??šđ??ź â&#x2C6;&#x2014; đ?&#x2018;&#x17E; = 1,0 â&#x2C6;&#x2014; 1,0 â&#x2C6;&#x2014; 1,28 + 1,5 â&#x2C6;&#x2014; 1,0 â&#x2C6;&#x2014; 2 = 4,28 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 KFI=1,0 (medium consequence class)17.

Serviceability limit state combination: đ?&#x2018;&#x201D; + đ?&#x2018;&#x17E; = 0,8 + 3 = 3,28 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 The values are multiplied by the length of the tread: đ?&#x2018;&#x2DC;đ?&#x2018;

đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161;

-

4,8 đ?&#x2018;&#x161;2 â&#x2C6;&#x2014; 1 đ?&#x2018;&#x161; = 4,8

-

3,28 đ?&#x2018;&#x161;2 â&#x2C6;&#x2014; 1 đ?&#x2018;&#x161; = 3,28 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161; (load acting on the step in SLS).

(load acting on the step in ULS);

đ?&#x2018;&#x2DC;đ?&#x2018;

The steps are considered as simply supported beam. The effective length is 6 m.

EC 1 EN1990 DK NA:2007, table A1.2.A, table A1.2.B

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Maximum moment (ULS): 1 1 đ?&#x2018;&#x20AC;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ = đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; 2 = â&#x2C6;&#x2014; 4,8 â&#x2C6;&#x2014; 62 = 21,6 đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161; 8 8 Maximum shear (ULS): 1 1 đ?&#x2018;&#x2030;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ = đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; = â&#x2C6;&#x2014; 3,28 â&#x2C6;&#x2014; 6 = 9,84 đ?&#x2018;&#x2DC;đ?&#x2018; 2 2 Bending moment verification: đ?&#x153;&#x17D;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; â&#x2030;¤ đ?&#x2018;&#x2DC;â&#x201E;&#x17D; â&#x2C6;&#x2014; đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; đ?&#x2018;?â&#x201E;&#x17D;2 200 â&#x2C6;&#x2014; 3002 = = 3 â&#x2C6;&#x2014; 106 đ?&#x2018;&#x161;đ?&#x2018;&#x161;3 6 6 đ?&#x2018;&#x20AC; 21,6 â&#x2C6;&#x2014; 106 = = = 7,2 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 đ?&#x2018;&#x160; 3 â&#x2C6;&#x2014; 106

đ?&#x2018;&#x160;= đ?&#x153;&#x17D;đ?&#x2018;&#x161;đ?&#x2018;&#x2018;

đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; = đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2DC; â&#x2C6;&#x2014;

đ?&#x2018;&#x2DC;đ?&#x2018;&#x161;đ?&#x2018;&#x153;đ?&#x2018;&#x2018; 1,3 â&#x2C6;&#x2014; đ?&#x203A;ž3

đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2DC; = 32 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 (Characteristic bending strength of GL32h) đ?&#x2018;&#x2DC;đ?&#x2018;&#x161;đ?&#x2018;&#x153;đ?&#x2018;&#x2018; = 0,7 (Glued laminated timber, Service Class 1, Long Term action)18 đ?&#x203A;ž3 = 1,0 (Normal Inspection level). đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; = 32 â&#x2C6;&#x2014;

0,7 = 17,23 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 1,3 â&#x2C6;&#x2014; 1 đ?&#x153;&#x17D;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; = 1,13

đ?&#x2018; đ?&#x2018; < 1,1 â&#x2C6;&#x2014; 17,23 = 18,95 2 đ?&#x2018;&#x161;đ?&#x2018;&#x161; đ?&#x2018;&#x161;đ?&#x2018;&#x161;2

Shear verification đ?&#x153;?đ?&#x2018;&#x2018; â&#x2030;¤ đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2018; Net Area is used. As the diameter of the bolts is unknown, a reduction of 10% is used.

3 đ?&#x2018;&#x2030;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ 3 9,84 â&#x2C6;&#x2014; 103 đ?&#x153;?đ?&#x2018;&#x2018; = â&#x2C6;&#x2014; = â&#x2C6;&#x2014; = 0,27 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 2 đ??´đ?&#x2018;&#x203A;đ?&#x2018;&#x2019;đ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;&#x153; 2 0,9 â&#x2C6;&#x2014; 200 â&#x2C6;&#x2014; 300 đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2DC; = characteristic shear strength đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2018; = đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2DC; â&#x2C6;&#x2014;

18

đ?&#x2018;&#x2DC;đ?&#x2018;&#x161;đ?&#x2018;&#x153;đ?&#x2018;&#x2018; 0,7 = 3,8 â&#x2C6;&#x2014; = 2 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 1,3 â&#x2C6;&#x2014; đ?&#x203A;ž3 1,3 â&#x2C6;&#x2014; 1

EC 5

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đ?&#x153;?đ?&#x2018;&#x2018; = 0,27

đ?&#x2018; < đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2018; = 2 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 đ?&#x2018;&#x161;đ?&#x2018;&#x161;2

Deflection Deflection is checked in the Serviceability limit state. đ?&#x2018;Ł=

5 đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; 4 384 đ??¸đ??˝

đ?&#x2018;

đ??¸ = 13700 đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 (Mean value of Modulus of elasticity for GL32h) đ??˝=

đ?&#x2018;?â&#x201E;&#x17D;3 300 â&#x2C6;&#x2014; 2003 = = 16 â&#x2C6;&#x2014; 106 đ?&#x2018;&#x161;đ?&#x2018;&#x161;4 12 12 5 3,28 â&#x2C6;&#x2014; 60004 đ?&#x2018;Ł= = 20,2 đ?&#x2018;&#x161;đ?&#x2018;&#x161; 384 13700 â&#x2C6;&#x2014; 20 â&#x2C6;&#x2014; 107

The deflection is considered acceptable.

The beam dimension on each side of the panel will be 100x300mm and when there are 2 panels side by side makes the same section as on beam calculations above (200x300mm).

Stair Calculation In order to calculate the necessary dimensions of the riser and tread, the following calculation has been done: Height of the ramp: 1,4 m Number of steps in each ramp: 8 Riser of each step: 0,175 m Blondel formula is used:

2đ?&#x2018;&#x; + đ?&#x2018;Ą = 62 á 64 đ?&#x2018;?đ?&#x2018;&#x161;ď&#x192; đ?&#x2018;Ą = tread = 28 đ?&#x2018;?đ?&#x2018;&#x161; đ?&#x2018;&#x; Inclination of the ramp: đ?&#x203A;ź = tanâ&#x2C6;&#x2019;1 đ?&#x2018;Ą = 32°.

The steps are supported by the beam in the wall on one side and they are connected to it by bolts.

On the other side, they are supported by steel bars, connected to an external beam.

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The following dimensions are used in the calculation below:

The steps are made in glued laminated timber (GL 32h).

The following loads acting on each step: -Self weight: đ?&#x2018;&#x201D; = 0,8 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 -Imposed load19: đ?&#x2018;&#x17E; = 3 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 Ultimate limit state combination: 1,0 â&#x2C6;&#x2014; đ??žđ??šđ??ź â&#x2C6;&#x2014; đ?&#x2018;&#x201D; + 1,5 â&#x2C6;&#x2014; đ??žđ??šđ??ź â&#x2C6;&#x2014; đ?&#x2018;&#x17E; = 1,0 â&#x2C6;&#x2014; 1,0 â&#x2C6;&#x2014; 0,8 + 1,5 â&#x2C6;&#x2014; 1,0 â&#x2C6;&#x2014; 3 = 5,3 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 KFI=1,0 (medium consequence class)20.

Serviceability limit state combination: đ?&#x2018;&#x201D; + đ?&#x2018;&#x17E; = 0,8 + 3 = 3,8 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 The values are multiplied by the length of the tread: đ?&#x2018;&#x2DC;đ?&#x2018;

đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161;

-

5,3 đ?&#x2018;&#x161;2 â&#x2C6;&#x2014; 0,28 đ?&#x2018;&#x161; = 1,5

-

3,8 đ?&#x2018;&#x161;2 â&#x2C6;&#x2014; 0,28 đ?&#x2018;&#x161; = 1,06 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161; (load acting on the step in SLS).

(load acting on the step in ULS);

đ?&#x2018;&#x2DC;đ?&#x2018;

The steps are considered as simply supported beam. The effective length is 1 m.

Maximum moment (ULS): 1 1 đ?&#x2018;&#x20AC;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ = đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; 2 = â&#x2C6;&#x2014; 1,5 â&#x2C6;&#x2014; 12 = 0,19 đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161; 8 8 Maximum shear (ULS): 1 1 đ?&#x2018;&#x2030;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ = đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; = â&#x2C6;&#x2014; 1,5 â&#x2C6;&#x2014; 1 = 0,75 đ?&#x2018;&#x2DC;đ?&#x2018; 2 2

19

EC 1 EN1990 DK NA:2007, table A1.2.A, table A1.2.B

20

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Bending moment verification: đ?&#x153;&#x17D;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; â&#x2030;¤ đ?&#x2018;&#x2DC;â&#x201E;&#x17D; â&#x2C6;&#x2014; đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; đ?&#x2018;?â&#x201E;&#x17D;2 280 â&#x2C6;&#x2014; 602 = = 16,8 â&#x2C6;&#x2014; 104 đ?&#x2018;&#x161;đ?&#x2018;&#x161;3 6 6 đ?&#x2018;&#x20AC; 0,19 â&#x2C6;&#x2014; 106 = = = 1,13 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 đ?&#x2018;&#x160; 16,8 â&#x2C6;&#x2014; 104

đ?&#x2018;&#x160;= đ?&#x153;&#x17D;đ?&#x2018;&#x161;đ?&#x2018;&#x2018;

600 0,1 ( đ?&#x2018;&#x2DC;â&#x201E;&#x17D; = đ?&#x2018;&#x161;đ?&#x2018;&#x2013;đ?&#x2018;&#x203A; { â&#x201E;&#x17D; ) = 1,26 1,1 kh is the factor that increase the bending strength in case of depth in bending less than 600 mm.21 kh=1,1. đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; = đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2DC; â&#x2C6;&#x2014;

đ?&#x2018;&#x2DC;đ?&#x2018;&#x161;đ?&#x2018;&#x153;đ?&#x2018;&#x2018; 1,3 â&#x2C6;&#x2014; đ?&#x203A;ž3

đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2DC; = 32 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 (Characteristic bending strength of GL32h) đ?&#x2018;&#x2DC;đ?&#x2018;&#x161;đ?&#x2018;&#x153;đ?&#x2018;&#x2018; = 0,7 (Glued laminated timber, Service Class 1, Long Term action)22 đ?&#x203A;ž3 = 1,0 (Normal Inspection level). đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; = 32 â&#x2C6;&#x2014;

0,7 = 17,23 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 1,3 â&#x2C6;&#x2014; 1 đ?&#x153;&#x17D;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; = 1,13

đ?&#x2018; đ?&#x2018; < 1,1 â&#x2C6;&#x2014; 17,23 = 18,95 đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 đ?&#x2018;&#x161;đ?&#x2018;&#x161;2

Shear verification đ?&#x153;?đ?&#x2018;&#x2018; â&#x2030;¤ đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2018; Net Area is used. As the diameter of the bolts is unknown, a reduction of 15% is used.

3 đ?&#x2018;&#x2030;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ 3 0,75 â&#x2C6;&#x2014; 103 đ?&#x153;?đ?&#x2018;&#x2018; = â&#x2C6;&#x2014; = â&#x2C6;&#x2014; = 0,08 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 2 đ??´đ?&#x2018;&#x203A;đ?&#x2018;&#x2019;đ?&#x2018;Ąđ?&#x2018;Ąđ?&#x2018;&#x153; 2 0,85 â&#x2C6;&#x2014; 60 â&#x2C6;&#x2014; 280 đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2DC; = characteristic shear strength đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2018; = đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2DC; â&#x2C6;&#x2014;

đ?&#x2018;&#x2DC;đ?&#x2018;&#x161;đ?&#x2018;&#x153;đ?&#x2018;&#x2018; 0,7 = 3,8 â&#x2C6;&#x2014; = 2 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 1,3 â&#x2C6;&#x2014; đ?&#x203A;ž3 1,3 â&#x2C6;&#x2014; 1 đ?&#x153;?đ?&#x2018;&#x2018; = 0,08

đ?&#x2018; < đ?&#x2018;&#x201C;đ?&#x2018;Łđ?&#x2018;&#x2018; = 2 đ?&#x2018; /đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 đ?&#x2018;&#x161;đ?&#x2018;&#x161;2

Deflection

21 22

EN 1994 EC 5

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Deflection is checked in the Serviceability limit state. đ?&#x2018;Ł= đ??¸ = 13700

đ??˝=

đ?&#x2018; đ?&#x2018;&#x161;đ?&#x2018;&#x161;2

5 đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; 4 384 đ??¸đ??˝

(Mean value of Modulus of elasticity for GL32h)

đ?&#x2018;?â&#x201E;&#x17D;3 280 â&#x2C6;&#x2014; 603 = = 5 â&#x2C6;&#x2014; 106 đ?&#x2018;&#x161;đ?&#x2018;&#x161;4 12 12 đ?&#x2018;Ł=

5 1,06 â&#x2C6;&#x2014; 10004 = 0,2 đ?&#x2018;&#x161;đ?&#x2018;&#x161; 384 13700 â&#x2C6;&#x2014; 5 â&#x2C6;&#x2014; 106

The deflection is considered acceptable.

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Middle Step - calculation Dimension of the step: AXB=1X1 m.

The following loads act on the middle step: -Self weight: đ?&#x2018;&#x201D; = 0,8 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 -Imposed load23: đ?&#x2018;&#x17E; = 3 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 Ultimate limit state combination: 1,0 â&#x2C6;&#x2014; đ??žđ??šđ??ź â&#x2C6;&#x2014; đ?&#x2018;&#x201D; + 1,5 â&#x2C6;&#x2014; đ??žđ??šđ??ź â&#x2C6;&#x2014; đ?&#x2018;&#x17E; = 1,0 â&#x2C6;&#x2014; 1,0 â&#x2C6;&#x2014; 0,8 + 1,5 â&#x2C6;&#x2014; 1,0 â&#x2C6;&#x2014; 3 = 5,3 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2

Serviceability limit state combination: đ?&#x2018;&#x201D; + đ?&#x2018;&#x17E; = 0,8 + 3 = 3,8 đ?&#x2018;&#x2DC;đ?&#x2018; /đ?&#x2018;&#x161;2 Uniformly distributed load (ULS): 5,3 â&#x2C6;&#x2014; đ??ľ = 5,3

đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161;

Maximum moment: 1 1 đ?&#x2018;&#x20AC;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ = đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; 2 = â&#x2C6;&#x2014; 5,3 â&#x2C6;&#x2014; 12 = 0,66 đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161; 8 8 Maximum shear force: đ?&#x2018;&#x2030;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ =

đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; 5,3 â&#x2C6;&#x2014; 1 = = 2,65 đ?&#x2018;&#x2DC;đ?&#x2018; 2 2

VERIFICATION đ?&#x2018;?â&#x201E;&#x17D;2 60 â&#x2C6;&#x2014; 10002 = = 1 â&#x2C6;&#x2014; 107 đ?&#x2018;&#x161;đ?&#x2018;&#x161;3 6 6 đ?&#x2018;?â&#x201E;&#x17D;3 60 â&#x2C6;&#x2014; 10003 đ??˝= = = 5 â&#x2C6;&#x2014; 109 đ?&#x2018;&#x161;đ?&#x2018;&#x161;4 12 12 đ?&#x2018;&#x160;=

0,66 â&#x2C6;&#x2014; 106 đ?&#x2018; = 0,066 < đ?&#x2018;&#x201C;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; â&#x2020;&#x2019; đ?&#x2018;&#x201A;đ??ž 7 1 â&#x2C6;&#x2014; 10 đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 3 2,65 â&#x2C6;&#x2014; 103 đ?&#x2018; đ?&#x153;?= â&#x2C6;&#x2014; = 0,066 â&#x2020;&#x2019; đ?&#x2018;&#x201A;đ??ž 2 60 â&#x2C6;&#x2014; 1000 đ?&#x2018;&#x161;đ?&#x2018;&#x161;2

đ?&#x153;&#x17D;đ?&#x2018;&#x161;đ?&#x2018;&#x2018; =

đ??ˇđ?&#x2018;&#x2019;đ?&#x2018;&#x201C;đ?&#x2018;&#x2122;đ?&#x2018;&#x2019;đ?&#x2018;?đ?&#x2018;Ąđ?&#x2018;&#x2013;đ?&#x2018;&#x153;đ?&#x2018;&#x203A;:

5 3,8 â&#x2C6;&#x2014; 10004 â&#x2C6;&#x2014; â&#x2030;&#x2026;0 384 13700 â&#x2C6;&#x2014; 5 â&#x2C6;&#x2014; 109

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Beam Below, the calculation of the beam marked as red in the sketch:

The beam has been calculated as simple supported beam.

In order to determine the load that acts on the beam, the following calculation has been done: Number of steps on the beam: 7 Load from one step (ULS combination): 0,75đ?&#x2018;&#x2DC;đ?&#x2018; Total load on the beam: 7 â&#x2C6;&#x2014; 0,75 = 5,25 đ?&#x2018;&#x2DC;đ?&#x2018; Length of the beam: 2,6đ?&#x2018;&#x161; Uniformly distributed load on the beam:

5,25đ?&#x2018;&#x2DC;đ?&#x2018; 2,6đ?&#x2018;&#x161;

= 2,02

đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161;

Density of the timber (GL32h): 430 đ?&#x2018;&#x2DC;đ?&#x2018;&#x201D;/đ?&#x2018;&#x161;3 Volume of the beam: 0,12 â&#x2C6;&#x2014; 0,12 â&#x2C6;&#x2014; 2,6 = 0,037 đ?&#x2018;&#x161;3 Weight: 430 â&#x2C6;&#x2014; 0,037 = 15,91 đ?&#x2018;&#x2DC;đ?&#x2018;&#x201D; â&#x2030;&#x2026; 0,16 đ?&#x2018;&#x2DC;đ?&#x2018; Uniformly distributed load (self weight):

0,16 đ?&#x2018;&#x2DC;đ?&#x2018; 2,6 đ?&#x2018;&#x161;

= 0,06

đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161;

Load perpendicular to the beam:

đ?&#x2018;&#x17E; = 1,7 + 0,05 = 1,75

đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161;

Load parallel to the beam:

Maximum moment: 1 1 đ?&#x2018;&#x20AC;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ = đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; 2 = â&#x2C6;&#x2014; 1,75 â&#x2C6;&#x2014; 2,62 = 1,48 đ?&#x2018;&#x2DC;đ?&#x2018; đ?&#x2018;&#x161; 8 8 PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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Maximum shear force: đ?&#x2018;&#x2030;đ?&#x2018;&#x161;đ?&#x2018;&#x17D;đ?&#x2018;Ľ =

đ?&#x2018;&#x17E;đ?&#x2018;&#x2122; 1,75 â&#x2C6;&#x2014; 2,6 = = 2,28 đ?&#x2018;&#x2DC;đ?&#x2018; 2 2

Load in the steel bars

It is possible to identify three different cases, as shown in the sketch below.

Bar: 1

1

1

ď&#x192; 2 load from the 1st step + 3 load from the 2nd step

2

ď&#x192; 3 load from the 2nd step

3

ď&#x192; 3 load from the 2nd step + 3 load from the 3rd step

1

1

1

Bar 1 (worst case): Axially loaded Load from 1 step: 0,75 đ?&#x2018;&#x2DC;đ?&#x2018; 1

1

Load in the bar: đ?&#x2018; = (2 + 3) â&#x2C6;&#x2014; 0,75 = 0,625 đ?&#x2018;&#x2DC;đ?&#x2018; đ??´đ?&#x2018; =cross section area of the steel bar 235

đ?&#x2018;

đ?&#x2018;&#x201C;đ?&#x2018;˘đ?&#x2018;&#x2018; = 1,15 = 204,35 đ?&#x2018;&#x161;đ?&#x2018;&#x161;2 = design tensile stress of the steel PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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𝐴𝑠 ≥

0,625 ∗ 103 = 3,06 𝑚𝑚2 204,35

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𝑁 ≤1 𝐴𝑠 ∗ 𝑓𝑢𝑑

3,06 𝑟≥√ = 0,7 𝑚𝑚 2𝜋 Steel bars with diameter of 8 mm are used.

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Column Calculation â&#x20AC;&#x201C; first try

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Column calculation â&#x20AC;&#x201C; second try

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Interview It has been made an interview to Jens Peter Mølgaard [Annex 11], straw bale house owner since 2005, to know the experience of living in a Straw bale house, with an interior finish with plaster. It will give an opinion of an expert living in straw house and will proportionate the experience to know if it would be worthy to build one and live in it. He has solve some problems/questions/doubts in order to drive the authors to a better solution.

XXVIII. Bibliography and webgraphy http://pulligny38.free.fr/linotte/documents/Dimensionnement_puits_canadien.pdf http://www.strongtie.com/ http://www.geus.dk/UK/data-maps/Pages/default.aspx http://www.calculatoredge.com/optical%20engg/air%20flow.htm http://www.friland.org/?page_id=1688 http://www.folkecenter.net/gb/rd/architecture/strawbale_house/ http://naturalhomes.org/ecohousemap.htm?strawbale http://passivepaille.free.fr/ http://www.isover.co.uk/saint-gobain-multi-comfort/about-multi-comfort/case-studies/komfort-husenedenmark https://uhdspace.uhasselt.be/dspace/bitstream/1942/14813/1/Paper%20PLEA%202012_Verbeeck.pdf http://www.ijramr.com/sites/default/files/issues-pdf/298.pdf https://en.wikibooks.org/wiki/Straw_Bale_Construction https://en.wikibooks.org/wiki/Straw_Bale_Construction/Print_version http://www.sbi.dk/download/pdf/jma_slides_halmhuse.pdf https://upload.wikimedia.org/wikipedia/commons/1/16/Straw_Bale_Construction.pdf https://www.wpi.edu/Pubs/E-project/Available/E-project-011411160348/unrestricted/MQP_B10_Jafferji_Raczka_Wang.pdf http://strawbale.sustainablesources.com/ http://www.equalparenting-bc.ca/abba/adobe-pdfs/Best-HomePower/Contents/Green%20Building/HP101_pg14_Magwood.pdf Books: “The ecology of building materials” Bjørn Berge "Structural Timber Design to Eurocode 5" Jack Porteous, Abdy Kermani "Hazardous building materials" (Steve Curwell, Bob Fox, Morris Greenberg, Chris March) 2002 “EN 1990 - Eurocode 0” PREFABRICATED STRAW PASSIVE HOUSE IN DENMARK

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“EN 1995 - Eurocode 5”

“The environmental design pocketbook" Sofie Pelsmakers 2015 "A practical guide to renewable energy" Christopher Kitcher 2012 "Practical Design of Timber Structures to Eurocode 5", Hans Larsen and Vahik Enjily, 2009

Books from Lars Keller: “Building with straw bales” by Barbara Jones 2002 “The straw bale house” by Athena Swentzell, Bill Steen and David Bainbridge 1994 “The independent home” (living well with power from the sun, wind, and water) by Michael potts 1993 Poele à accumulation ‘le meilleur du chauffage au bois” (Vital Bies and Marie Milesi) 2010

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We would like to thanks firstly our consultant, Arnaldo Landivar for his help and support. His advices during the project had improved substantially the quality of our work. We also want to thank Jens peter and Lars Keller that we have met in Friland, they have been really helpful as they know a lot about straw constructions and rocket stove. They gave us information and shared knowledge with us that we could not find easily on internet. Henrik Bjørn from VIA allowed us to improve our parameters about mussel shells foundations thanks to the study he gave us.

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