ZEMUSIC | WP6.4: Design Guide for Steel Intensive nearly-Zero Energy Buildings

WP 6.4

DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

ZERO-ENERGY SOLUTIONS FOR MULTI-USE STEEL-INTENSIVE COMMERCIAL BUILDINGS

ZEMUSIC

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS



Grant agreement no. RFSR-CT-2011-00032 Zero Energy Solutions for Multi-functional Steel Intensive Commercial Buildings (ZEMUSIC)

Deliverable Report WP6.4 Design Guide for Steel Intensive nearly Zero Office Buildings

Author: Andrea Botti

University of Surrey

Contributors: Mark Lawson

University of Surrey

Jyrki Kesti, Petteri Lautso, Tarmo Mononen Bernd Döring, Vitali Reger Date: 28.03.2015 Work Package No.: 6

RWTH Aachen

Ruukki

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

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EXECUTIVE SUMMARY Aim of the project

The objective of the project is to identify ways in which sustainable value can be created in steel intensive commercial multi-storey buildings by improving energy efficiency and integrating on-site renewable energy generation, on a path to nearly-zero energy levels.

The project also has a commercial target, based on market needs. New innovative technical solutions were studied and developed for the steel intensive parts, such as a long span structural frame and a thermal pile foundation system. An integrated building envelope was developed to include passive and active features, such as shading and integration with M&E, to show ways in which they can contribute to value creation.

The research approach allowed the entire building to be optimised for cost and performance in terms of energy saving, offering a range of possibilities of practical measures to achieve the goal, while linking steel structures to a key value demand in the current market.

Results

The focus of the project was on systems where both the building fabric and the structure participate actively to the building’s energy balance. The system level concepts developed in WP2 for different climates and performance levels in Europe provide valuable information of wider scope, which can be utilised outside the boundaries of this project. The innovative floor system with integrated MEP routings developed in WP3 can lead to a cost effective solution for sophisticated ventilation distribution and radiant heating and cooling systems, achieving a high energy efficiency and a superior level of indoor comfort.

The use of energy piles for seasonal balancing of heating and cooling offers great potential for climate zones where cooling and heating demands are comparable on an annual basis. In a commercial building with exhaust heat, ‘cold’ energy piles are a very cost effective for making heat available when needed; where excess heat is not otherwise available, integrated solar heat systems can be used for charging the soil with heat during winter.

Energy efficiency resulting from the choice of exterior facade has been assessed, revealing how geographic location, window to wall ratio, energy demand for different HVAC technologies, and requirements for solar shading play a significant role.

The project covered a variety of technical solutions, that each participate in the design of nearly Zero Energy Buildings (nZEB). Virtual reference buildings were specified for three different climates to assess the value potential of the solutions studied, by means of dynamic energy simulations, and to perform Life Cycle Cost (LCC) calculations. Results showed that for the nZEB to be cost-effective over its life cycle, special attention has to be paid to controlling the installed costs of the energy efficiency investments for example through building integration.

The Design Guide Both the methodology used for the current research project and the design solutions are summarised in the form of the present Design Guide, with the goal of disseminating the results to inform future building design.

The Design Guide presents architectural information on how nearly Zero Energy Buildings can be designed for three European climate zones, by testing measures on a 6 storey reference office building for Helsinki, London and Bucharest. The design includes the use of a long span structural system, combined with a novel chamber flooring system that houses radiant cooling panels and other MEP services. Alternative options are presented, to allow the flooring system to be adapted to be part of the ventilation strategy, while reducing heating and cooling loads.

General guidance on the choice of geometric and thermal parameters for the design of façades is also included, with a focus on appropriate solar shading and the integration of Photovoltaic systems with different parts of the building envelope.

The Life Cycle Costing study shows pay back periods in purely energy costs, which is less than 10 years relative to current energy efficient design.

CONTENTS 1 Definitions and background 1.1 Energy Performance of Buildings Directive and nZEB 8 1.2 Types of zero energy 8 1.3 Terminology and balance concept 8 1.4 Balancing principle and nZE methodology 9 1.5 European targets for Low and nearly-Zero Energy Buildings 10 1.6 Hierarchical approach for achieving Zero Energy / Zero Carbon Buildings 13 1.7 Lessons learned from for Net Zero Energy Solar Buildings: Case Studies and Solution Sets 14

2 Building orientation and form 2.1 Reference building 18 2.2 Building orientation 19 2.3 Building form 20 2.4 Atria and sun-spaces 20 2.5 Atrium for the reference building 22

3 Building frame and depth of plan 3.1 Environmental consideration to building depth 26 3.2 Building structure: short span system 26 3.3 Building structure: long span system 27

4 Floor system 4.1 Pre-fabricated steel floor system and integration with MEP system 32 4.2 Radiant ceiling (heating and cooling) 33 4.3 Radiant ceiling embedded in a PCM layer 36 4.4 PCM without radiant ceilings - air based system with free cooling at night 38 4.5 Air based system with mixed ventilation of PCM within chambers (no radiant cooling) 40 4.6 PCM without radiant ceilings, considering natural ventilation of office room 42

5 Building envelope 5.1 Environmental considerations and design criteria 46 5.2 Fenestration and glazing parameters 46 5.3 Facade orientation 48 5.4 Fenestration and window-to-wall ratio 49 5.5 Solar shading 51

6 HVAC strategies and on-site renewable energy generation 6.1 Baseline and nearly zero-energy HVAC systems overview 56 6.2 On-site renewables: energy piles and ground source heat pumps 58 6.3 On-site renewables: solar thermal 62 6.4 On-site renewables: solar photovoltaic 64 6.5 Study of integrated modular façades 68

7 Final optimum solutions 7.1 Main design features for the nearly Zero Energy case 74 7.2 Hierarchy of measures for the nearly Zero Energy case 75 7.3 Simulations with optimum solutions: total energy demand and consumption 76 7.4 Life Cycle Cost analysis 78

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

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1 DEFINITIONS AND BACKGROUND

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Definitions and background

1.1 Energy Performance of Buildings Directive and nZEB The Energy Performance of Buildings Directive (EPBD) 2010/31 [1] introduced the term “Nearly zero-energy buildings” (nZEB) and specified definitions and time frames for its implementation: “Article 2(2) - Definitions Nearly zero-energy building’ means a building that has a very high energy performance, as determined in accordance with Annex I. The nearly zero or very low amount of energy required should be covered to a very significant extent by energy from renewable sources, including energy from renewable sources produced on-site or nearby;” Article 9 - Nearly zero-energy buildings “Member States shall ensure that: (a) by 31 December 2020, all new buildings are nearly zero-energy buildings; and (b) after 31 December 2018, new buildings occupied and owned by public authorities are nearly zero-energy buildings.

Member States shall draw up national plans for increasing the number of nearly zero-energy buildings. These national plans may include targets differentiated according to the category of building.”

The strategic directive leaves the interpretation and implementation of measures, as well as methodologies for calculations to member states. To date, National applications of the EPBD requirements are not fully defined and how close should “nearly-zero” be to “zero” still remains unanswered.

1.2 Types of zero energy Different types of nZEB have been outlined over the recent years [2] :

Net Zero Site Energy

The building/site produces at least an equivalent amount of energy, as that used per annum when accounted for at the building/site.

Net Zero Source Energy

The building/site produces an equivalent amount of energy, as that used per annum when accounted for at the source. Source energy indicates the primary energy used to generate and deliver energy to the building/site.

Net Zero Energy Costs

The amount an energy supplying utility pays to the building/site owner for energy exported to the grid, and is at least equivalent to the amount the building/site owner pays to the energy supplying utility for energy, services, connections fees etc.. per annum.

Net Zero Energy Emissions

The building/site produces at least the same amount of emissions free renewable energy as it uses from emission producing energy sources per annum.

1.3 Terminology and balance concept Building system boundary

The boundary at which to compare energy flows flowing in and out the system [3] . It includes: • Physical boundary: can encompass a single building or a group of buildings; determines whether renewable resources are ‘on-site’ or ‘off-site’.

• Balance boundary: determines which energy uses (e.g. heating, cooling, ventilation, hot water, lighting, appliances) are included in the balance.

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Some definitions are reported from European Standard:

Energy grid

The supply system of energy carriers, such as electricity, gas, thermal networks for district heating, biomass etc.. Grids here considered are two-way grids, that can deliver energy to a building/site and occasionally receive energy back from it. This is common for electricity grid and thermal networks.

Loads

Building’s energy demand, specified per each energy carrier. Heating/cooling loads, which indicates the heat to be delivered to or extracted from a conditioned space by a heating or cooling system to maintain the intended temperature during a given period of time, not taking into account the building services.

Delivered energy

Total energy, expressed per energy carrier, supplied to the building to satisfy the uses taken into account (heating, cooling, ventilation, domestic hot water, lighting, appliances etc..).

Generated energy

Building’s energy generation, specified per each energy carrier. The generation may not coincide with exported energy due to self-consumption of energy generated on-site.

Exported energy

Energy, expressed per energy carrier, delivered by the building through the system boundary and used outside the system boundary.

1.4 Balancing principle and nZE methodology The analyses and recommendations in this document present the nearly zero energy solutions, which were studied in the Work Packages described in the Executive Summary.

Net ZEB balance is satisfied when the supply meets demand over a chosen period of time, nominally a year. The net zero energy balance can be determined either from the balance between delivered and exported energy or between load and generation. The former choice is named import/export balance and the latter load/generation balance. A third option is possible, using monthly net values of load and generation and it is named monthly net balance [4] .

The chosen method for assessing the nZE levels is an annual balance between the delivered energy and the generated energy, both expressed in and kWh/m2,NFA /year, or more simply kWh/m2 y. The starting point is the assessment of the performance of the ‘reference building’, which represents a new building which meets the minimum requirements set by the national building codes.

Starting from such reference case, the pathway to a Net ZEB is given by the balance of two actions:

energy supply [kWh]

1. Reduction of energy demand (x-axis) by means of energy efficiency measures; 2. Energy generation (electricity as well as thermal energy) by means of energy supply options to obtain enough credits (y-axis) to achieve the balance.

net zero balance line

Net ZEB energy supply

reference building

energy demand [kWh]

energy efficiency

Figure 1. Balance methodology between energy demand and supply for a reference building, compared to a NetZEB

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Definitions and background

1.5 European targets for Low and nearly-Zero Energy Buildings 1.5.1. European climate zones A characterization of climate zones has been used in order to orient the design process of steel intensive nearlyzero energy buildings by testing and evaluating the suitability of certain design strategies to various certain climatic zones. Building upon methods such as Olgyay’s chart and the Köppen-Geiger climate classification and its updates [5] , which were used as design guidance, ECOFYS has suggested a climate classification for Europe in order to enable the normalisation of energy consumption to a limited number of variables. This allowed a certain degree of extrapolation of building performance originally calculated for some representative buildings for each climate zone, and extend them to the whole climate zones.

1.5.2. Definitions of nZEB - Energy Performance and Renewable Energy Shares The performance of nZEBs is mainly calculated in terms of primary energy consumption units (kWh/m2y), as this was identified by the EU as the best common metric across the member states to allow a direct comparison between the levels of performance of new buildings across member states be feasible. Table 1 gathers the energy performance for residential and non-residential buildings for different climate zones, together with the national legislation reference for different member states [6] .

Helsinki

London

Bucharest

Figure 2. ECOFYS climate zones set for comparison of building performance [6] On the map three capital cities are indicated, namely London, Helsinki and Bucharest, which were chosen for the ZEMUSIC project to be representative of three separate climatic zones.

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Table 1. Overview of the nZEB definitions, in quantitative terms, currently available in Europe [6]

NZEB Definition Energy Performance (EP)

Reference National legislation providing the definition

EP-value R.E.S. Energy Uses Building Type (kWh/ in EP Metric included m²y) calc

Zones Cyprus 1-2

180 210 32 54 60 34

no no n.d. n.d. n.d. n.d.

P.E. P.E. P.E. P.E. P.E. P.E.

45

yes

P.E.

95yes 2.5*(V/S)

P.E.

95yes 2.5*(V/S)

P.E.

60

n.d.

P.E.

30

yes

P.E.

40

yes

P.E.

France

50 70 110

no no no

P.E. P.E. P.E.

htg, clg, vent, DHW, light, aux

Ireland

45

n.d.

E.Ld.

htg, vent, DHW, light

Res.

0

yes

EPC

htg, clg, vent, DHW, light

Res. / NonRes.

necessary but not EPG2012 quantified

20

yes

P.E.

Res.

51-56%

25

yes

P.E.

Non-Res.

51-56%

50

yes

P.E.

100 100 90

yes yes yes

P.E. P.E. P.E.

Latvia

95

n.d.

P.E.

htg, clg, vent, DHW, light

Res. / NonRes.

-

Lithuania

<0.25

n.d.

EP indC

htg

Res. / NonRes.

50%

Zone 3

Zone Country

Slovakia

Belgium BXL

Zone 4

Belgium Walloon Belgium Flemish

Nether lands

Zone 5

Denmark

Estonia

htg, clg, DHW htg, DHW htg, clg, vent, DHW, light htg, DHW, appl htg, clg, vent, DHW, light, appl htg, clg, vent, DHW, appl htg, DHW, appl htg, clg, vent, DHW, aux

R.E.S. Res. Non-Res.

Apartments Family houses Office Schools Individual dwellings

Res. Non-Res. Res.

Office

25% 25% 50% 50% 50% 50%

Non-Res. Res., schools, office and services

Res. / NonRes.

Office, schools Non-Res. Res.

htg, clg, vent, DHW htg, clg, vent, DHW, light

Brussels Air, Climate and Energy Code

-

Res.

Office (NV) Office (AC)

-

-

Schools

NZEB Action Plan

Non-Res.

50%

Regional Policy Statement

>10 kWh/m²y Energy Decree > 10 kWh/m²y RT2012 Building Regulations Part L

BR10 Detached houses Apartments Office Schools

Res. Non-Res.

-

EP : Energy Performance; R.E.S. : Renewable Energy Share; P.E. : Primary Energy; E.Ld. : Energy Load; htg : heating; clg = cooling; DHW : Domestic How Water; appl. : appliances; aux : auxiliary system Res. : Residential; Non-Res : Non-Residential;

VV No 68:2012

Cabinet Regulation 383/2013 Building Tech.

Reg STR 2.01.09:2012

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Definitions and background

1.5.3. Finland - FinZEB In Finland, the national project FinZEB was carried out in 2014 to set up background information for Finnish near Zero Energy requirements [7] . The proposal recommends four requirements: • Maximum heat losses through building envelope and from ventilation.

• Maximum power demand for electricity.

• Maximum total energy consumption (E-value).

• Other requirements (e.g. renewable energy share).

The building’s total energy consumption E-Value (kWh/m2/y), is the annual net delivered energy of the building weighted by an energy carrier factor (e.g. 1.7 for electricity). The annual net delivered energy is the total purchased energy from central sources and it includes all energy use (heating, ventilation, cooling, lighting and electrical appliances). Energy generated from on-site renewables is not included within the delivered energy.

However, it can reduce the E-value if it is consumed on-site, or if it is exported to the grid. Table 2 shows the proposed E-values for new buildings for Finnish Building Regulations, which are due to be published by 2017.

Table 2. Current and proposed E-values for nZEB in Finland [7]

Building Type

2013 Maximum E-value

2017 Maximum E-value for nZEB (Proposed)

Detached house

160 / 204

120 / 204

Multi-storey apartment block

130

116

-11%

Office

170

90

-47%

School

170

104

-39%

Day nursery

170

107

-37%

Commercial building

240

143

-40%

Sport hall

170

115

-32%

Hotels etc.

240

182

-24%

Hospital

450

418

-7%

Reduction from 2013

Table 3. Max Fordham Green Office Sustainability Matrix [8] Criteria Proposed Building Regulations 1 CO2 Emission design target (kgCO2/m2/yr) 2 DEC rating 3 Energy use (kWh/m2/yr) Heating & DHW load Electrical base load IT and small power 4 On site energy generation 5 U-values (W/m2K) Wall Average window Roof Ground floor 6 Airtightness @50 Pa

Minimum Standard

Best Practice

Innovative

2010 Part L Regs

2013 Part L Regs

2016 Part L Regs

30

21

8

C rating

B rating

A rating

61 16 48 Up to 20% local planning

46 15 41

30 13 33

>20%

>50%

0.2 1.4 0.15 0.15 3.5 m3/h·m2 (BCO)

0.15 1.1 0.12 0.12 2 m3/h·m2

0.35 (Part L 2010) 2.2 (Part L 2010) 0.25 (Part L 2010) 0.25 (Part L 2010) 10 m3/h·m2 (Part L)

Pioneering 2019 Part L - ‘Zero Carbon’ 0 or “Carbon Neutral” A+ rating 15 12 26 > 100% on site or agreed off-site 0.1 0.8 0.1 0.1 1 m3/h·m2

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1.5.4. United Kingdom - Zero Carbon Standard The UK set a target for new homes to meet the Zero Carbon Standard from 2016, in advance of the Energy Performance of Buildings Directive (EPBD) target for all new buildings in the EU to be ‘Nearly Zero-Energy Buildings’ from 2020. However, while the nZEB definition in most of the EU member states covers all new buildings from 2020, the Zero Carbon Standard only refers to domestic buildings.

A definition for non-domestic buildings is due to be developed shortly in the UK, to allow the 2019 target to include all new non-domestic buildings to be Zero Carbon as well.

With regards to office buildings, engineers Max Fordham developed in 2005 a series of matrices to be used as a communication tool to promote discussion on suitable low carbon solutions during early design stages [8] . They cover operational emissions for specific building types, indicating projected fabric efficiencies and energy use for future Zero Carbon standard. An extract from the ‘Green Office - New Build’ matrix is shown in Table 3.

1.6 Hierarchical approach for achieving Zero Energy / Zero Carbon Buildings In order to meet a Zero Carbon standard for buildings, the UK Government supports a hierarchical approach [9] , that is fairly similar to that for nZEB (Figure 3). The approach prioritises, in turn:

Energy Efficiency measures

To ensure that buildings are constructed to very high standards of fabric energy efficiency and services efficiency, based on the delivered energy required to provide space heating, cooling, ventilation and lighting (kWh/m²/year).

On-site Energy Generation

Low and Zero Carbon (LZC) energy sources (including renewable energy) applied after the energy efficiency measures, since LZC sources are normally cost-effective when they are employed to satisfy a low energy demand.

Allowable Solutions

A range of additional beneficial measures to offset ‘residual emissions’, for example exporting low carbon or renewable heat to neighbouring developments or investing in LZC community heating.

Figure 3. Hierarchical approach for Zero Carbon Buildings in the UK [9]

1.6.1. Differences between nZEBs and Zero Carbon definitions Even though the metrics of energy consumption and carbon emission are different, units can be converted from one form to the other by using appropriate factors. The hierarchical approach for achieving Zero Carbon Homes priorities the Fabric Energy Efficiency Standard (FEES), which is the proposed maximum space heating and cooling energy demand. While this is still expressed with the same metric (kWh/m2/year) as nZEBs primary energy, the two measurements are different and should not be compared directly. The mechanism of Allowable Solutions for Zero Carbon standard, which permits to off-set CO2 off site by investing in carbon reducing projects within the UK, is also different from the nZEB definition, where a ‘nearby’ option for energy production is included, possibly limiting the choice to solutions directly linked to the building.

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Definitions and background

1.7 Lessons learned from for Net Zero Energy Solar Buildings: Case Studies and Solution Sets The International Energy Agency (IEA) developed, a part of SubTask C from IEA Task40/Annex52 project, a Net Zero Energy Buildings Database, which focused on a benchmark set of NZEBs from around the world to identify the most appropriate solutions sets that define this type of building [11] . About 30 zero energy buildings and projects where short-listed into a database, upon establishing the following criteria: 1. Innovative solution sets and/or technologies clearly identified for each project; 2. Net ZEB Lessons learned (feedback from Architect/builder); 3. Net ZEB Energy performance < 50% standard buildings (primary and final energy) ; 4. Energy supply/integration of Renewable Energy; 5. Monitoring mandatory (energy measurements); 6. Mismatch management (Near or Net zero energy building); 7. Indoor environment data (Temperature, RH, Illuminances…).

For the selected projects the design team produced unique responses to achieve set energy targets, by combining design approaches which included passive and active energy strategies. Solution sets, or sets of passive design solutions, energy efficiency solutions and/or renewable energy solutions, were studied [10] : • Whole Building Solution Set, including solutions aimed at lowering the energy use of the whole building; • Building Challenge Solution Set, including solutions aimed at reducing the energy needed by a particular building challenge (e.g. heating, cooling, lighting, plug loads etc....).

Figure 5 summarises the frequency of use of the various solution sets, expressed in percentage of the total number of buildings reviewed. For example, over 95% of the selected projects feature advanced building envelopes, with solar shading and integrated photovoltaic. Also the impact of building form is important, particularly for the heating dominated climate zones.

Figure 4. Map of the Net ZEB projects worldwide

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

0%

40%

60%

80%

8% 0%

On-site

33%

7%

83% 93%

Building footprint 58% 50%

Geothermal 17%

Biomass-fired boilers

7% 17%

Biomass powered CHP Wind turbines

100%

29%

RENEWABLE ENERGY SYSTEMS SOLUTIONS

At-site

20%

15

8% 0% 100% 100%

Photovoltaics 83%

Solar thermal

71%

Ceiling fans, evaporative cooling 0% Efficient air source heat pump

33% 42%

ENERGY EFFICIENT SYSTEMS SOLUTIONS

29% 67%

Radiant cooling

14% 50%

Radiant heating

14%

UFAD or 0% displacement ventilation 0% 25%

Hot water heat recovery

43%

Mechanical air heat recovery

58% 93% 42%

Load management

57% 33%

Advanced lighting control

14% 42%

Efficient office equipment

29% 42%

Efficient appliances

64% 92%

Energy efficient lighting

71%

Blinds for glare control 0%

0% 17% 0% 25% 29%

Skylights

58% 57%

Window to wall ratio 17%

Ground cooling

7% 92%

Natural ventilation Site vegetation

36% 8% 0% 100% 93%

Solar shading

75% 86% 67% 93%

Thermal mass Passive solar heat gain 17%

Advanced glazing

57% 83% 93%

Advanced envelope Thermal zoning Optimised building form

8%

PASSIVE SOLUTIONS

Solar tubes

Figure 5.â&#x20AC;&#x192; Analysis of solution sets by type of climate, employed on a benchmark set of NZEBs (IEA Task 40) [10] Horizontal bars show the frequency of use of different measures, for heating dominated climates and mixed heating and cooling ones HEATING DOMINATED CLIMATES

43% 92% 93%

MIXED HEATING AND COOLING

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

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2 BUILDING ORIENTATION AND FORM

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Building orientation and form

2.1 Reference building In WP2, the energy demands for heating, cooling, domestic hot water (DHW) and lighting were studied for a typical office building in the three chosen locations: Helsinki (Finland), London (UK) and Bucharest (Romania).

A multi-storey commercial office building located in the technology park of Jyväskylä, Finland was chosen as the reference building for the energy simulations (Figure 6).

Figure 6. Bird-eye view of the reference building

Such choice was instrumental in order to link the assumptions made in WP2 with realistic components and system types, and most importantly to draw comparisons between the results of the simulations with realistic building measurements. While data presented in this report is based entirely on virtual models, realistic measurements, components, and system types utilised and monitored in the building were considered.

The building consists of six-storeys with a floor-to-floor height of 3.6m, as shown in Figure 24. The building comprises 3 wings, two of which are deep plan (south-west and north-west, both 17m deep) and one shallowplan (south-east, 12m deep).

The building is oriented approximately 41.3 deg from north, therefore its main external façades are oriented towards south-east, south-west and north-west.

Figure 7. Solar radiation and shadowing masks for the reference building

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2.2 Building orientation Orientation is a significant factor to determine a building’s energy demands. It needs to be carefully considered to allow heat gains in winter while reducing solar gains in summer, optimising the daylight while avoiding glare. Different parts of a building do not have equal access to the sun, and as such each orientation should be treated differently to achieve optimal environmental behaviour.

The figures below show the amount of global solar radiation that vertical façades facing south, east and west would receive on a typical summer and winter days; for a climate like that of Bucharest, the solar radiation on a south-facing facade is fairly high in winter, creating an advantageous potential for passive solar strategies.

However, the radiation on façades oriented both south and west is very high in summer, leading to a severe risk of overheating if not controlled through appropriate shading.

W/m2

W/m2

SUMMER

500 450 400

E

350

S

500 450 400

W

350

300

300

250

250

200

200

150

150

100

100

50

50

0

WINTER

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

S E W 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

HOURS

HOURS

Figure 8. Intensity of solar radiation on vertical façades, Helsinki

SUMMER

W/m2 500

W/m2 500

S

450 400

450 400

W

E

350

350

300

300

250

250

200

200

150

150

100

100

50

50

0

WINTER

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

S E

W

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

HOURS

HOURS

Figure 9. Intensity of solar radiation on vertical façades, London

SUMMER

W/m2 500 450 400

E

S

W/m2 500

W

450 400

350

350

300

300

250

250

200

200

150

150

100

100

50

50

0

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

WINTER

0

HOURS

Figure 10. Intensity of solar radiation on vertical façades, Bucharest

S

E

W

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

HOURS

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Building orientation and form

2.3 Building form Surface-to-volume (S/V) ratio can have a significant impact on heat gains and losses, particularly for cold climates, where the benefits of compact building forms with regards to heating demands have been documented [12] .

Location and value property has a considerable impact on building form: • Office buildings located in a city centre, where land is very expensive, are designed to maximise the value of lettable floor area; as such, tall buildings (over 15 storeys) with compact footprint are fairly common. These type of buildings have very low S/V ratios.

• Office buildings located egde-of-town (or out-of-town), on the other hand, can afford larger footprint and more ‘human scale’, often organised in wings or distributed around a central courtyard. These type of buildings include a wider range of forms and massing, and they generally have higher S/V ratios.

Figure 11. Two office building by Bennetts Associates Architects. New Street Square in central London (left) and Hampshire County Council HQ in Winchester, (right)

2.4 Atria and sun-spaces Sun-spaces and glazed atria are glazed spaces that are thermally separated from the buildings they are connected to. These spaces can be fully, partially or not heated, depending on the building type and occupancy.

• A sun-space is a relatively small glazed space, often attached to the side of the building. While sun-spaces are a fairly common passive strategy for dwellings, they are less common for large office buildings.

• An atrium is a glazed space, attached to or integrated with a large building, or placed between two or more such buildings. Atria are a common feature in office buildings, particularly in centre-of-town office building where high rental costs justify to combine spaces for distribution with energy saving strategies.

The different types of atria are illustrated in Figure 12.

The core atrium is the most common atrium type, providing a glazed courtyard in the centre of the building, with adjacent spaces on all sides. The external envelope of this type of atrium for is limited to the glazed roof.

The presence of an atrium allows to benefit for very advantageous passive strategies for heating, cooling, ventilating and provide daylighting the building.

CORE ATRIUM

Figure 12. Types of atria

INTEGRATED ATRIUM

LINEAR ATRIUM

ATTACHED ATRIUM

ENVELOPE ATRIUM

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2.4.1. Heating An atrium acts as a buffer reducing transmission losses from the adjacent spaces to the ambient and may also provide heat for the adjacent spaces. It is used to displace auxiliary heating by solar gain transfer from atrium to the adjacent spaces. Thus, the predominant orientation of the atrium aperture should be south, and the glazing should be vertical (to reduce overheating risks in summer).

Collected solar radiation has to be stored in interior mass in building components exposed directly to the winter sun.

Night-time heat losses have to be reduced by using good thermal quality materials in the envelope glazing and in the walls and windows separating the atrium from the rest of the building.

2.4.2. Cooling An atrium can be designed to induce natural ventilation and to prevent undesirable solar gains. Natural ventilation can be facilitated by a vertical stack effect and by proper placement of air inlets and outlets. Inlets should be placed at the bottom of the atrium (and/or induced cross circulation should be included), and sufficient exhaust air vents should be placed at the very top.

Night-time convective cooling of building mass structure can be achieved by cross ventilation, with air passing from the ambient through the adjacent spaces and out via the atrium space.

2.4.3. Daylighting An atrium can be used to provide additional light to the adjacent spaces. The key issues are daylight availability, distribution, and utilization. The glazing of an atrium reduces the amount of available daylight inside, but as a consequence of the buffer effect of the glazing, the window area in the intermediate boundary can be increased without penalties in the form of higher heating energy consumption. Consequently, more daylight may be available in the adjacent spaces.

The amount available is determined by the overall design and by the properties of the walls and windows separating the atrium and the adjacent spaces. Atrium dimensions (height, length, width), determine the potential daylight aperture, and the size and position of windows in the intermediate boundary, as well as the reflectivity of the walls themselves, determine the amount of daylight penetrating into the adjacent spaces.

Figure 13. Benefits of atria for heating, cooling and daylighting purposes

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Building orientation and form

2.5 Atrium for the reference building The benefits of introducing an atrium can be assessed by means of thermal simulations. The reference building (Option 0 in Figure 14) is simplified into a regular ‘U shape’ to enable comparisons (Option 1). Then the massing is rearranged to form a central courtyard (Option 2). Finally a glazed roof is placed on top of the atrium (Option 3). The values in terms of annual solar gains and heat losses for different floor level are shown in Figure 15. It is apparent that the atrium offers a significant reduction of the solar gains as well as the heat losses through the building envelope, and is therefore a very attractive solution for nearly Zero Energy buildings.

0

YEARLY SOLAR GAINS (kWh/m2)

1 10 5 0

Reference Building

2

External Envelope Area 2853m2 Uwall 0.2 Uwindow 1.0

0

LEVEL 0 LEVEL 1 LEVEL 2 LEVEL 3 LEVEL 4

ATRIUM

-5 -10 -15

3

-20 -25

External Envelope Area 3192 Uwall 0.2 Uwindow 1.0

Envelope Area (m2) Uwall Uwindow

Ext. 2232 0.2 1.0

-30

Int. 960 0.8 1.8

-35 -40 -45

Figure 14. Alternative building forms for the reference building

YEARLY HEAT LOSSES (kWh/m2)

Figure 15. Chart showing annual solar gains and heat losses

ORIGINAL

Figure 16. Sketch showing the original building and the alternative version with a courtyard atrium

WITH ATRIUM

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

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3 BUILDING FRAME AND DEPTH OF PLAN

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Building frame and depth of plan

3.1 Environmental consideration to building depth Office buildings accommodate activities that involve often high densities of occupation, medium-to-high lighting levels and high equipment densities, all of which are responsible for significant internal heat gains and energy demand.

In deep-plan offices, comfort conditions are achieved by means of mechanical services and artificial lighting, which lead to a high energy use. Narrow plan offices, on the other hand, can benefit from better daylight levels and potential for natural ventilation, which allows a reduction in running costs, including cooling energy, lighting and services maintenance. However, the capital costs of the naturally ventilated offices are generally higher, particularly due to higher specifications for the building envelope and a higher facade-to-floor ratio. The main differences are shown in Table 4.

Table 4. Environmental considerations related to building depth (adapted from [13])

Narrow plan

Deep plan

Cellular/two zone planning Views out Individual control Natural ventilation Natural lighting Lower energy consumption Lower running costs Higher capital cost

Open plan/multi/zone planning Internal areas Constant conditions Mechanical ventilation Artificial lighting Higher energy consumption Higher running costs Lower capital cost

3.2 Building structure: short span system The reference building consists of three wings, as illustrated in Figure 17. Of those, two are regarded as narrow plan (12m wide) and two are deep plan (17m).

The short span system is based on the use of slim floor (WQ) beams in which services are located below the beams. The WQ beams span 8.1m along the axis of the building and the chamber floor system is orientated across the building with a maximum span of 7m.

The WQ beams can be perforated to align with the chambers.

N

A 12m clear span solution without intermediate columns uses a shallower fabricated beam version of the 17m span case (considered below).

As mentioned in the previous chapter, narrow plan areas (or buildings) offer a good potential for implementing natural ventilation as a main strategy for cooling and ventilation. However within the present study, the development of the innovative long-span and integrated floor structure has resulted in adopting the same HVAC system (including thermal zoning, serviced areas etc..) for both long and short span cases.

Figure 17. Top view of the reference building, with indication of narrow plan and deep plan wings

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3.3 Building structure: long span system Long span construction eliminates internal columns, and creates more usable space both at the office level and also in the basement car parking.

In this design, illustrated in Figure 18, the primary beams span 17m (16.4m between columns), and support secondary beams of 8.1m span. The primary beams are fabricated tapered sections that lead to an overall construction depth of 900m (without a raised floor). The beams reduce (taper) to a minimum depth of 300 mm at the columns, which means that the structure is perceived to be minimal depth at the façades.

Regular 400 mm diameter openings are provided in the fabricated section in the middle part of the span, to allow for effective routings in longitudinal direction for ventilation ducts, cable bundles and heating, cooling and sprinkler plumbing.

At the building façade, IPE 300 beams with welded bottom plate support the chamber floor. These beams are perforated by 200 mm diameter openings, aligned with the floor steel chambers, to allow air in and through the chamber, to achieve night-time cooling. Alternatively, WQ slim floor beams may be used.

The top flange of the steel beam is chosen as 220 mm width so that it occupies the width of one chamber.

Shear connectors are welded to the top flanges of the beam to provide composite action with the concrete topping over the beam and so the composite beams are sufficiently stiff for low vibration response over 16.4m span. The structural steel weight of the long span system is compatible with efficient design, due to the use of tapered beams and composite action of the beams with the slab.

The double layer steel-concrete composite floor panels enable routings and heating and cooling systems to be integrated into the floor structure in the transverse direction (facade to facade). The chamber floor system is orientated across the building so that the chambers may be linked to the façade to permit air to be draw in through the chambers, which potentially may be used to provide night-time cooling of the floor slab, as well as housing services, radiant panels and pipes.

IPE 300 IPE 330

UC305

IPE 330

3.6m 5.5m

6.0m

car park

8.1m 5.5m Figure 18. Three-dimensional view of the long span steel frame for one structural bay

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Building frame and depth of plan

This possibility is considered later in the development of the façade systems. The chamber floor system is designed so that one chamber in five or six is in-filled with concrete and two reinforcing bars in order to provide the required structural and fire resistance. Composite action with a thin concrete topping ensures the slab is sufficiently stiff for spans up to 6m . The long span tapered beam system provides the added benefits of integration of ducts in the central part of the building, which are used to provide cooling of the internal space, as well as providing a minimal structural depth at the facade lines. Although not considered directly in the Design Guide, the freedom of internal planning that the long span system provides is an additional valuebenefit that clients recognise. The column spacing is also selected to facilitate efficient basement car parking.

The chamber floor system can also be delivered with its integrated services, and in future developments, even with its concrete topping in the form of wide pre-cast concrete units.

The main service routings through the perforated beams and the chamber flooring system are shown in Figure 19. The main ducts run along the axis of the building, and the radiant panels are incorporated into the chambers.

Figure 19. Modular service routing to be integrated with the floor slab

Three service zones are created in the long span system, as shown in Figure 20: • Two perimeter zones are cooled via the chamber floor system and have a taller floor-ceiling height in order to maximise the levels of daylight and reduce the need for artificial lighting.

• An internal zone with a shallower floor-ceiling height, which is serviced centrally, and this space is intended to be used for meeting rooms and ‘break out’ space. Air ducts pass through the service openings in the beams in this zone. In both cases, a raised floor system can be provided as an option.

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

A. Passive zone

B. Serviced zone

Permanent workspace

Meeting rooms, break out, temporary workspace

27

A. Passive zone

Permanent workspace

3.3m

6m

5m

6m

Figure 20. Diagram of office section/use for the long span option Table 5. Advantages and disadvantages of long span system

Advantages

Disadvantages

Internal columns are eliminated giving greater usable space Car park space with is provided in the basement Large openings in the beam are provided for services Minimum structural depth at the façade

Slightly higher use of steel than in the short span system Deeper floor system (although services are within the beam depth)

Energy simulations were performed to assess the effect of different floor depths on energy use, particularly in relation to building orientation and window size. Two layouts, the first with wall-to-wall depth of 12m accommodating 8 desks (at a density of ca. 6m2/person), the second with a depth of 17m accommodating 12 desks (at a slighty higher density). For each iteration the a N-S orientation and a E-W orientation were tested, together with two alternative in terms of window sizes.

The results illustrated in Figure 21 show that the floor depth is arguably the main factor affecting energy demands for buildings designed with very good fabric efficiency. Since heat losses and solar gains (leading to cooling demands) are very low, the reduction of daylight availability for the deep plan office (17m) results in higher lighting energy use, which makes a significant difference in the total energy figures. kWh/m2y

LIGHTING

VENTILATION

COOLING

40

17m

35 30

HEATING

17m

17m 12m

12m

17m

17m

17m 12m

12m

12m

Big N Small S

Big E Small E Small W Big W

17m

17m 12m

12m

12m 17m

12m

25 20 15 10 5 0

Big N Big S

Big E Big W

Small N Small N Big S Small S

Small E Small W

Baseline

Figure 21. Energy use (heating, cooling, fans and lighting) for floor depth of 12m and 17m, Helsinki

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

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29

4 FLOOR SYSTEM

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Floor system

4.1 Pre-fabricated steel floor system and integration with MEP system The pre-fabricated chamber floor system is based on a 1.35m wide module in order to be consistent with a column spacing of 8.1m along the building façade. This module could be reduced to 1.25m for 7.5m column spacing. As shown in Figure 22, a total of 6 chambers of 225 mm width are provided in each 1.35m wide module of which one chamber is filled as a reinforced ‘beam’. The chamber is manufactured in cold formed steel of 1 to 1.2mm thickness and is 200 mm deep to achieve un-propped spans of up to 6m. The chamber depth can be increased to 250 mm to achieve un-propped spans of 7.5m.

6m

1.35 m 2.7 m Figure 22. Prefabricated composite floor system

Figure 23. Modular service routing can be integrated with the flooring system

The concrete layer placed over the chamber floor is taken nominally as 100 mm thick for R90 or R120 minutes fire resistance, although it could be reduced to 70 mm for R60. Two T20 bars are provided in the 300mm deep ribs, and this reinforced section is combined with the composite action of the chamber system, so the floor is very stiff. The reinforced section is also required for fire resistance as the chamber system is considered to be ineffective in fire.

As previously discussed, the integration of modular service routings through the perforated beams and with the chamber flooring system is a significant advantage for the chosen solution. While the main ducts run along the axis of the building,ventilation terminals, radiant panels, the sprinkler system and electrical wiring can be incorporated into the chambers (Figure 23).

Advantages and disadvantages of the integrated steel floor system are listed in Table 6 below.

Table 6. Advantages and disadvantages of long span system

Advantages

Disadvantages

Chamber system incorporates cooling pipes and electrics Chamber system may be used for night cooling The floor can be fully pre-fabricated

Deeper floor system (although services are integrated within the beam depth)

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4.2 Radiant ceiling (heating and cooling) 4.2.1. Description of technology The system is based on the flooring element presented in WP 3.1. The chambers can be used for air and cabling, additionally the three chambers in the middle of each half-module are equipped with a piping system for heating and cooling purposes (Figure 24). The lower steel sheet of the chambers is important for the distribution of heat/cold from the pipes in the horizontal direction, and furthermore the steel sheet acts as heat exchanging surface. This form of construction effectively acts as a radiant ceiling.

KEY

2750mm 1350mm

MEP Steel chamber 225x200mm Mineral wool insulation 20-40mm PCM

Supply air duct Extract air duct Htg/Clg pipes Sprinkler Electric cabling

Figure 24. Steel floor system with MEP routing and pipes for radiant heating and cooling

4.2.2. Working principle The cold or heat from the pipes is transferred into the steel sheet and to the room. A numerical study has shown, that an additional steel profile (“Ω profile”) is needed for a better transmission and uniformity of heat transfer. This effect is shown in Figure 25.

The numerical results lead to a cooling capability of 35 W/m² expressed per unit floor area at a temperature difference between the room and water of 8°K (i.e. 4.4 W/m²K of deck surface). The heating capability reaches 56 W/m² at a 17°K temperature difference (i.e. 3.3 W/m²K of total deck surface). For the cooling case, the heat transfer is supported by the natural convection, therefore the heat transfer coefficient of the surface is better than for the heating case, where the heat transfer is working against the natural convection.

case 1 - radiant ceilings ΔΔT= 17 K qH= 56 W/m2

ΔT= -8 K qC= 35 W/m2

Tp = 30 °C

TOP = 21 °C

Winter Day Office hours (08:00)

Tp = 21 °C

TOP = 25 °C

Summer Day Office hours (14:00) TOUT= -5 °C

Figure 25. Working principle of case 1: radiant ceilings for heating and cooling

TOUT = 30°C

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Floor system

22.5 30.0 20.0 27.5 35.0 17.5 HELSINKI 25.0 32.5 15.0 22.5 30.0 12.5 20.0 27.5 10.0 17.5 25.0 0 15.0 22.5 12.5 20.0 10.0 17.5 15.0 12.5 35.0 10.0 32.5

0

24

48

time [h]

72

96

24

48

time [h]

72

96

25 35 20 30 15 40 25 10 35 20 5 30 15 0 25 120 10 20 5 15 0 120 10

96

5 40 0 120 35

TOP [°C]

TOUT [°C]

LONDON 0

24

48

Temp [°C]

Temp [°C]

Temp [°C]

30.0 27.5 35.0 25.0 32.5

15.0 12.5 35.0 10.0 32.5

time [h]

72

24

48

time [h]

72

96

24

48

time [h]

72

96

30 40 25 35 20 30 15 40 25 10 35 20 5 30 15 0 25 120 10 20 5 15 0 120 10

96

5 40 0 120 35

LONDON

22.5 30.0 20.0 27.5 35.0 17.5 LONDON 25.0 32.5 15.0 22.5 30.0 12.5 20.0 27.5 10.0 17.5 25.0 0 15.0 22.5 12.5 20.0 10.0 17.5

QC [W/m²]

0

BUCHAREST 0

24

48

30.0

time [h]

72

radiant cooling radiant [W/m²] cooling radiant [W/m²] cooling [W/m²]

HELSINKI

25.0 32.5

radiant cooling radiant [W/m²] cooling radiant [W/m²] cooling [W/m²]

Temp [°C]

Temp [°C]

Temp [°C]

Figure 25 shows the working principle with two snapshots for an average winter / summer day, including room (operative) temperature, outside temperature and heating / cooling capability. The cooling is switched on TOP [°C] [°C] QC [W/m²] OUT which a mean when the room temperature exceeds 24 °C,Tat water temperature of 18 °C circulates through 40 35.0 the coolingHELSINKI pipes. While this provides sufficient cooling for a moderate summer climate, the system capability is not32.5 sufficient for the hot summer in Bucharest: as Figure 26 shows while cooling is35active the whole day, the room30.0 temperature still exceeds 27 °C. Nevertheless the system is very efficient for both London and Helsinki as TOP [°C] TOUT [°C] QC [W/m²] 30 27.5 summer night-time conditions are cooler.

40 35.0

radiant cooling radiant [W/m²] cooling radiant [W/m²] cooling [W/m²]

Temp [°C]

Temp [°C]

Temp [°C]

30 40 25 BUCHAREST 35 20 22.5 30.0 30 20.0 27.5 15 40 35.0 25 17.5 BUCHAREST 25.0 32.5 10 35 15.0 20 22.5 30.0 5 30 12.5 20.0 27.5 15 10.0 0 25 17.5 25.0 0 24 48 72 96 120 10 time [h] 15.0 20 22.5 5 Figure12.5 26.

Temperatures and cooling power (W/m²) of radiant ceiling for warmest summer week for the three locations 20.0 15 10.0 0 TOP =17.5 room operative temperature; TOUT = outdoor air temperature; QC = cooling power of radiant ceiling 0 24 48 72 96 120 10 time [h] 15.0 5 12.5 27.5 35.0 25.0 32.5

10.0

0 0

24

48

time [h]

72

96

120

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

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4.2.3. System requirements The solution with radiant cooling is sufficient for the climate in central and northern Europe (considering normal office use and external shading). For the hotter climates, the cooling capability is insufficient, and therefore it has to be combined with an additional cooling (such as mechanical ventilation with cooling coil).

A mean water temperature of 18 °C can be reached with an inlet temperature of 17 °C and a volume flow of about 15 litres/h per m² area through the deck elements. The practical tests have shown that thermal contact from the pipe to the lower steel sheet hat to be manufactured very carefully, otherwise the thermal performance of the deck elements will be lower than expected.

4.2.4. Advantages and disadvantages The advantages of this integrated radiant cooling system are presented below.

Advantages Fully integration of heating/cooling system Low additional material costs Heating / cooling capability sufficient for most temperate climate cases Good control of room temperature Very fast reaction of the system

Disadvantages Limited cooling power (35 W/m² at 8 K temperature difference) Sufficient thermal contact from pipe to steel sheet has to be ensured in manufacture

34

WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Floor system

4.3 Radiant ceiling embedded in a PCM layer 4.3.1. Description of technology This variant of the system is based on the described radiant ceiling. Since the solution with radiant cooling is not sufficient for the hotter climates, the radiant cooling system can be combined with an additional PCM layer where the pipes are embedded in the PCM in the middle of each half-module as shown in Figure 5.

KEY

MEP Steel chamber 225x200mm Mineral wool insulation 20-40mm PCM

Supply air duct Extract air duct Htg/Clg pipes Sprinkler Electric cabling

Figure 27. Steel floor system with MEP routing and heating/cooling pipes embedded into a PCM layer

4.3.2. Working principle The PCM is able to absorb the heat when the temperature in the room increases. The cooling energy from the pipe passes not only into the steel sheet and it can also be used for a re-charging of the PCM around the pipe.

The PCM between the pipes leads to a reduction of the maximum temperature peaks (Figure 29). With the help of PCM, the system is still not able to keep the temperatures below 25 °C for warmer climates, but it reduces the cooling peaks and it could help reducing the additional energy demand.

case 2 - radiant + PCM ΔT= -8 K qc= 35 W/m2

TCE = 21 °C

TCE = 20 °C

TOP = 25 °C

Summer Day Office hours (14:00)

TOP = 22 °C

Summer Nght OOF hours (04:00) TOUT = 30 °C

Figure 28. Working principle of case 2: radiant ceilings for heating and cooling embedded in a PCM layer

TOUT = 16 °C

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS TOP [°C] 35.0

TOUT [°C]

TCE [°C]

QC [W/m²]

QA [W/m²]

HELSINKI

32.5

TOP [°C]

TOUT [°C]

TCE [°C]

QC [W/m²]

QA [W/m²]

40 25 35 20 30 15 25 10 20 5 15 0 24

48

72

time [h]

96

120

15.0

10 5

12.5 10.0

0 0

35.0

24

48

72

time [h]

96

120 40

LONDON

32.5

35

30.0

Temp [°C]

30

27.5 35.0 25.0 LONDON 32.5 22.5 30.0 20.0 27.5 17.5 25.0 15.0 22.5 12.5 20.0 10.0 17.5 0

30 40 25 35 20 30 15 25 10 20 5 15 0 24

48

72

time [h]

96

120

15.0

10

radiant coolingradiant [W/m²]cooling [W/m²]

Temp [°C] Temp [°C]

27.5 35.0 25.0 HELSINKI 32.5 22.5 30.0 20.0 27.5 17.5 25.0 15.0 22.5 12.5 20.0 10.0 17.5 0

radiant coolingradiant [W/m²]cooling [W/m²]

35

30.0

Temp [°C]

35

40

Figure12.5 29. Temperatures and cooling power (W/m²) of radiant ceiling for warmest summer week5 for Helsinki and London TOP =10.0 room operative temperature; TOUT = outdoor air temperature; TCE = ceiling temperature; 0 0 24 72 of inlet water.96 120 QC = cooling power of radiant ceiling; Q48 = cooling time [h] power A TOP [°C]

35.0

Tout [°C]

Tce [°C]

QC [W/m²]

QA [W/m²]

BUCHAREST 4.3.3.

System requirements 32.5

40 35

Temp [°C]

OP

C

A

20.0 27.5

15

radiant coolingradiant [W/m²]cooling [W/m²]

The solution with radiant cooling and PCM is slightly better than the radiant ceiling alone, at which temperature 30.0 30 Tce [°C] Q [W/m²]strategy.

Q [W/m²] T [°C]can beTout peaks27.5 or cooling power peaks cut,[°C]depending on the control It is sufficient for the climate 35.0 25For the hotter climates in central northern Europe (considering normal office use and external shading).40 25.0 and BUCHAREST 32.5 Bucharest), the cooling capability is still too weak, therefore it has to be combined 35 (example with an additional 20 22.5 30.0 option (mechanical ventilation with cooling coil). cooling 30 Temp [°C]

A mean °C and a volume flow 17.5 water temperature of 18 °C can be reached with an inlet temperature of 17 25 25.0 10 of about 15 l/h per m² area of deck elements.

The PCM mass can be quite small and in the calculation a PCM 15.0 20 the thermal inertia 22.5 layer12.5 of 14 kg/m² was considered for embedding of the pipes. However, regarding only 5 20.0 requirement, half of this amount would be enough.

15 10.0 17.5 0

0

24

48

time [h]

72

96

120

15.0 Advantages and disadvantages 4.3.4.

10 5

12.5

The advantages of this integrated radiant cooling system with a PCM layer are presented below.

10.0

0

0

Advantages

24

48

time [h]

Similar benefits as radiant ceiling Reduction of temperature peaks through PCM Recharging of the PCM through the pipes Reduction of cooling power peaks and shift of energy demand in off-peak hours

72

96

Disadvantages

120

Slightly lower capability of the radiant cooling PCM has no direct contact to the room Limited area for the PCM

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WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

Floor system

4.4 PCM without radiant ceilings - air based system with free cooling at night 4.4.1. Description of technology The system uses the chambers of the flooring system for air or cabling but not for cooling of the room. During the day, an additional centralised Air Handling Unit (AHU) is used to avoid temperatures in the room reaching an uncomfortable level. Night ventilation is used to cool down when the room is not occupied. Additionally a PCM layer is placed below the deck, and is therefore directly in contact with the room (Figure 30).

KEY

MEP Steel chamber 225x200mm Mineral wool insulation 20-40mm PCM

Supply air duct Extract air duct Htg/Clg pipes Sprinkler Electric cabling

Figure 30. Steel floor system with MEP routing and air ducts for supply/extract + PCM mounted on the underside of the floor slab

4.4.2. Working principle Figure 31 shows the temperatures (operative room temperature, outside temperature and the supplied temperature of the ventilation) of the described variation. Since the PCM is located directly to the room, it can interact with the room temperature efficiently and avoid temperature peaks during the day. If the temperature in the room exceeds 22 °C, the AHU is used for cooling of the supplied air when the room is occupied. After work, cooling through AHU is not necessary. Night ventilation with an increased air exchange about 4 ach ensures that the room is cooled down, and recharging of the PCM is achieved when the outside temperature is lower than the room temperature. The PCM and the AHU helps to avoid to high temperatures in the room but the system reaches its limits if the outside temperature is high, which is the case in hotter climates.

case 3 - air system + PCM TCE = 23 °C

TCE = 22 °C

TOP= 25 °C

TOP= 21 °C

Summer Day Office hours (14:00)

Summer Night OOF hours (04:00) TOUT= 30 °C

Figure 31. Working principle of case 3: PCM layer inside the steel chambers, without radiant ceilings

TOUT= 16°C

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS TOP [°C]

TIN [°C]

QC [W/m²] 8

30.0

TOP [°C]

35.0 27.5

TOUT [°C]

TCE [°C]

TIN [°C]

QC [W/m²]

8 2

30.0 22.5

6 0

27.5 20.0

4 -2

25.0 17.5

2 -4

22.5 15.0

0 -6

20.0 12.5

-2 -8 -4 -10 120 -6

17.5 10.0 0

24

48

time [h]

72

96

-8

12.5

-10 120

10.0 0

35.0

24

48

time [h]

72

96

10

LONDON

32.5

8 6

30.0 35.0 27.5

10 4

LONDON

32.5 25.0

8 2

30.0 22.5

6 0

27.5 20.0

4 -2

25.0 17.5

2 -4

22.5 15.0

0 -6

20.0 12.5

-2 -8 -4 -10 120 -6

17.5 10.0 15.0

0

24

48

time [h]

72

96

PCM coolingPCM [W/m²] cooling [W/m²]

15.0

Temp [°C] Temp [°C]

6 10 4

HELSINKI

32.5 25.0

37

10

HELSINKI

32.5

Temp [°C] Temp [°C]

TCE [°C]

PCM coolingPCM [W/m²] cooling [W/m²]

35.0

TOUT [°C]

-8

12.5

Figure 32. Temperatures and cooling power (W/m²) of PCM ceiling for warmest summer week for Helsinki and London -10 10.0 TOP = room operative temperature; TOUT 48 = outdoor air temperature; TCE =96ceiling temperature; 0 24 72 120 time [h] TIN = inlet (air supply) temperature; QC = cooling power of radiant ceiling.

TOP [°C] TOP [°C]

35.0

Tout [°C] Tout [°C]

Tce [°C] Tce [°C]

Tin [°C] Tin [°C]

QC [W/m²] QC [W/m²]

BUCHAREST 4.4.3.

System requirements 32.5 TOP [°C] above were TOP [°C]

10 8

Tce air-change [°C] Tin [°C] Tout [°C]with an achieved rate Tout [°C] Tce [°C] Tin [°C]

toQQ3C [W/m²] ACH [W/m²] C

PCM coolingPCM [W/m²] cooling [W/m²]

Temp [°C] Temp [°C]

6 The results presented up during working hours and an 30.0 inlet 35.0 temperature of 21 °C. These are moderate values, and are termed “supported ventilation”.

The ceiling has 10 4 27.5 BUCHAREST with 32.5 8 kg/m² of PCM, which is sufficient for a 24-h temperature cycle.

The air-change rate at night for cooling 8 2 25.0 down30.0 the PCM is set to 4 ACH, if the air flow is mechanically driven or naturally by 06operable windows.

22.5 4 by a higher air change -2 If the27.5 temperature conditions and/or the cooling loads are higher, this can be covered 20.0 rate 25.0 during the working hours and a lower air inlet temperature (e.g. 19 °C or 18 °C, 2 depending on position -4 17.5 and characteristic of the supply air diffusers.

0 22.5 -6 15.0 -2 -8

20.0 12.5

4.4.4.

17.5 10.0 Advantages and disadvantages The

0 15.0 advantages

24

48

time [h]

72

96

of this integrated PCM and air based system with free cooling

12.5

-4 -10 120 -6 at night

are presented below.

-8

Advantages

Disadvantages

High amount of PCM is possible 0 24 48 72 time [h] Routings for cooling pipes not necessary Easy integration of AHU in ventilation concept Recharging of PCM through night ventilation without additional cooling energy Variation of the parameters of AHU allows to cover a wide range of demands

Not as effective as radiant 120 cooling 96 Temperature of AHU limited for reasons of comfort Recharging of PCM dependent on night temperatures

10.0

-10

Investment costs and energy consumption for AHU

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Floor system

4.5 Air based system with mixed ventilation of PCM within chambers (no radiant cooling) 4.5.1. Description of technology A “mixed” ventilation is the combination of natural ventilation, typically by operable windows, and mechanical ventilation, with ambient air or pre-cooled air. For this design case, shown in Figure 33, natural ventilation of the room is provided together with mechanical ventilation of the chambers, which have an additional PCM layer on the inside.

KEY

MEP Steel chamber 225x200mm Mineral wool insulation 20-40mm PCM

Supply air duct Extract air duct Htg/Clg pipes Sprinkler Electric cabling

Figure 33. Steel floor system with MEP routing and air ducts for supply and extract, with PCM located into the steel chambers

4.5.2. Working principle The mechanical ventilation for the chambers allows a good control of the air flow rate and the temperature of the PCM, at which the ambient temperature and the avoidance of condensation are the limiting conditions.

The concrete in the floor slab and the additional PCM mass provide the thermal inertia of the system, which is cooled at night by air, and during the day the ceiling provides cooling for the inlet air. The cooling capability of the ceiling could be increased by additional pre-cooling of the air, and this might be interesting for climatic zones with high temperatures during the night.

case 4 - air system + night vent PCM in chamber TCE = 22 °C

TOP = 25 °C

Summer Day Office hours (14:00)

TOP = 22 °C

Summer Night OOF hours (04:00) TOUT = 30 °C

Figure 34. Working principle of case 3: PCM layer inside the steel chambers, without radiant ceilings

TOUT = 16 °C

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4.5.3.â&#x20AC;&#x2021; System requirements An air-change rate of about 4 ACH (related to the room volume) will be sufficient. Due to the large crosssection areas of the chambers the pressure losses are small. Pre-cooling of the air increases the range of suitable buildings and climate zones. Nevertheless, if the temperature of the ambient air is too high, the performance is limited, but for northern and central Europe this solution offers a significant improvement with much less additional energy demand.

4.5.4.â&#x20AC;&#x2021; Advantages and disadvantages The advantages of this integrated air based system are presented below.

Advantages

Disadvantages

Building users can control their indoor conditions Low additional investment costs Low additional energy demand Good control of thermal state of PCM

Limited cooling performance Suitable for moderate summers (northern, central Europe)

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Floor system

4.6 PCM without radiant ceilings, considering natural ventilation of office room 4.6.1. Description of technology In this solution, the ventilation of the room and the regeneration of the PCM is achieved by natural ventilation, based on operable windows or louvres. During the night, sufficient air change rate is needed, so that the air temperature in the room reduces, and in consequence, the PCM cools down for regeneration. Only the contact of the room air and the PCM is responsible for the performance of the PCM, and in this solution, there is no additional water-based or air-based system for the regeneration of the PCM (Figure 35).

4.6.2. Working principle The openings in the façade lead to a natural air flow in the room respectively in larger parts of the building.

During the day, this air change is mainly needed to provide the building users with fresh air. In the summer period, the air change at night is needed to remove excess energy from the building, at which the room temperature should be sufficiently low that the regeneration of the PCM is possible. In consequence, this technique is useful for climate zones with low temperatures during the night (northern or central Europe, and in warmer climates potentially for spring/autumn).

4.6.3. System requirements Also for this solution, an air change rate of about 4 h-1 will be sufficient, and this has to be considered for the sizing of the window openings. There are mathematical models available that allow the air change rate to be determined as a function of the window geometry, the external and internal temperatures and the wind speed.

On the other hand, air change should be terminated, when specific conditions occur: • the room temperature is reaching the minimal acceptable values (e.g. 18 °C at night) • the ambient temperature is higher than the room temperature • the weather conditions do not allow the windows to be opened (driving rain, etc..)

case 5 - PCM with natural ventilation TCE = 24 °C

TCE = 22 °C

TOP = 26 °C

Summer Day Office hours (12:00)

TOP = 20 °C

Summer Evening OOF hours (20:00) TOUT = 30 °C

Figure 35. Working principle of case 3: PCM layer inside the steel chambers, without radiant ceilings

TOUT = 16 °C

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Therefore, an automatic system for opening and closing the windows (or other openings) in the façade is needed. The actuators have to be linked with a central building control system, that gives the correct instructions according the conditions listed above.

The amount of PCM is mainly required to act over a daily temperature cycle, and about 10 kg/m² floor area is recommended

4.6.4. Advantages and disadvantages The advantages of the PCM based systems with natural ventilation are presented below.

Advantages

Disadvantages

Automation of openings in the facade is needed (e.g.: motor drive for windows) Openings in the façade at night might cause safety Building users like natural ventilation and operable windows problems (weather, break-in) No additional energy demand

Direct coupling of room temperature and state of PCM Limited cooling capability

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5 BUILDING ENVELOPE

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Building envelope

5.1 Environmental considerations and design criteria For most buildings, the facade strongly affects the building’s energy performance and the comfort of its occupants. To provide occupants with a comfortable and safe environment, a facade must fulfil many functions, such as providing views to the outside, resisting wind loads, supporting its own dead-load, allowing daylight to the interior spaces, preventing unwanted solar heat gain, protecting occupants from outside noise and temperature extremes, and resisting air and water penetration. Designers need to consider the external environment, building orientation, space dimensions, and occupants’ comfort expectations. Thermal, visual, and acoustic comfort are influenced by several factors, such as air temperature, humidity, solar radiation, wind speed, noise and external obstacles which can provide shading [14] .

The relative importance that is placed on the aforementioned criteria impacts design decisions, such as: • the properties of opaque materials: thickness and density of wall layers, thermal insulation, reflectivity; • the properties of transparent materials: number and thickness of layers, heat transmission, solar heat gain coefficient, visible light transmittance, light reflection.

5.2 Fenestration and glazing parameters Fenestration is a significant element of envelope design, from both aesthetic and performance perspectives, as it affects a building’s overall energy consumption, as well as its occupants’ well-being, health, comfort, and productivity. Technology advances have triggered the development of fenestration products that combine transparent yet energy-efficient façades. Standard glazing units now comprise two, three, or more layers of glass, while cavities can be filled with inert gases or aero-gel insulation to achieve very low U-value for the whole unit. Low-emissive, reflective, or ceramic frit coatings can be applied to the glass to reduce transmission of solar heat gain (as shown in Figure 36).

In Table 7, the main physical parameters for glazing are listed: Ug, g and TV are the most important ones as they maintain a direct relationship with energy demands for heating, cooling and lighting. Choosing between these sets of parameters is not simple and requires a definition of design priorities not only in terms of desired energy performance, but also with regards to such aspects as aesthetic appearance, cost and visual comfort.

Different climatic zones require different sets of characteristics for the building envelope. Triple glazing systems with argon-filling (as shown in Table 9) and low-e coating seem the most appropriate choice for buildings in a Northern climatic zone, as minimizing heat losses is of main importance. For southern climates, higher U values may be used, whilst lower g values are required to reduce summer heat gains.

Figure 36. Schematic energy flows through glazing Table 7. Main physical parameters for glazing elements

Parameter Ug

Unit

Term

W/m2K Heat transfer coefficient

g (SHGC)

--

Solar Heat Gain Coefficient,

b (N; SC)

--

Shading Coefficient =g/0,87

τe (DET)

%

Direct Energy Transmission

ρe (DER)

%

Direct Energy Reflection

αe (DEA)

%

Direct Energy Absorption

τV or TV (LT)

%

Light Transmission

ρV (LR)

%

Light Reflection

Ra(D65) (CRI)

%

Colour Rendering Index

S (LSGR)

---

Light to Solar Gain Ratio TV /g

TRA

NS

MIS HEAT SIO N

SO EN LAR ERG Y

R

EC EFL

TIO

LE REF

N

CTI

LE REF

CTI

ON

HE EN ATIN ERG G Y SO EN LAR ERG Y

ON

SECONDARY TRANSFER

SECONDARY TRANSFER

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Table 8. Facade design strategies for different climate zones.

Climate

Design strategies for sustainable façades

Heating- Solar collection and passive heating: collection of solar heat through the building envelope. dominated Heat storage and heat conservation. climates (Helsinki) Daylight: large glazed areas of the facade acceptable if combined with the use of high-performance glass.

Solar control: protection from direct solar radiation through self-shading (building form) or shading devices Cooling- Reduction of external heat gains: protection from solar heat gain by thermal insulation or by shading devices dominated climates Cooling: use of natural ventilation where environmental characteristics and building function permit.

Daylight: minimizing solar heat gain.

Mixed climates (London)

Solar control during warm seasons.

Solar collection and passive heating during cold seasons.

Daylight: generous glazed areas, combined with shading devices to keep summer solar gains low.

5.2.1. Commercial triple-glazing assemblies for nZEBs Table 9. List of main physical properties for selected commercial triple-glazing systems nZEB building applications Note: all glazed constructions are 6 - 16 - 4 - 16 - 4 mm, with argon filled cavities.

Manufacturer / Product

Tv

Saint-Gobain Cool-Lite SKN 174+Float (Planilux) Guardian Sun-Guard HP Green 64 #2+Float Glass Clear AGC / Glaverbel Stopray Clearvision 50 #2+Planibel Clear Guardian ClimaGuard D+Float Glass ExtraClear #5 Low-E AGC / Glaverbel Float (Planibel) Clear #3,5+Float (Planibel) Low-E Saint-Gobain Cool-Lite KN 169+Planitherm #5 Saint-Gobain Cool-Lite KB 159+Planitherm #5 AGC / Glaverbel Sunergy Clear #2+Planibel Low-E #3,5 AGC / Glaverbel Stopsol Supersilver Clear #1+Planibel Low-E #3,5 AGC / Glaverbel Float (Planibel) Dark Blue #3,5+Float (Planibel) Low-E AGC / Glaverbel Stopsol Clear #1+Planibel Low-E #3,5 Saint-Gobain Float (Planilux)+Planitherm #3,5 Guardian ClimaGuard Premium+Float Glass ExtraClear #5 Low-E Saint-Gobain Cool-Lite SKN 174+Planitherm #5 Guardian Sun-Guard HS SuperNeutral 62+Float Glass ExtraClear Low-E AGC / Glaverbel Stopray Elite on Clearvision #2+Planibel Low-E #3,5 AGC / Glaverbel Stopray Safir on Clearvision #2+Planibel Low-E #3,5 Saint-Gobain Cool-Lite ST 150+Planitherm #3,5

62 56 47 64 58 55 47 44 43 38 26 72 70 62 55 50 1.0 46 g 42

0.8

0.38 0.31 0.30 0.51 0.59 0.40 0.37 0.42 0.47 0.31 0.34 0.62 0.51 0.38 0.31 0.4 0.6 0.35 0.30 0.36

Ug

0.2

0.80 0.80 0.80 0.70 0.70 0.70 0.70 Ug 1.0 0.70 0.9 0.70 0.8 0.7 0.70 0.6 0.70 0.5 0.4 0.60 0.3 0.2 0.60 0.1 0.60 0 0.2 0.60 0.60 0.60 0.60

Ug

Ug 1.0

1.0

0.9

0.9

0.9

0.8

0.8

0.8

0.7

0.7

0.7

0.6

0.6

0.6

0.5

0.5

0.5

0.4

0.4

0.4

0.3

0.3

0.3

0.2

0.2

0.2

0.1

0.1 0

0.4 0.6 0.8

Tv > 0.6

1.0

1.0

Tv

g

Ug

Ug 1.0

0.9

0.9

0.8

0.8

0.7

0.7

0.8 1.0

g

0.8 1.0

1.0

Tv

g

0.4

0.4 0.6

0.6 0.8

0.8

0.4 < Tv < 0.5

Figure 37. Radial chart showing glazing systems from the table above, according to Ug, g and Tv values 1.0

0.4 0.6

0.2

0.6 0.8

0.5 < Tv < 0.6

0

0.4 0.6

0.8

0.8

0.2 0.4

0.6

0.6

1.0

0.2

0.4

0.4

0.4

1.63 1.81 1.57 1.25 0.98 1.38 1.27 1.05 0.91 1.23 0.76 1.16 1.37 1.63 1.77 0.6 1.43 0.8 1.53 1.0 Tv 1.17

0.1 0

0.2

0.2

LSG = g/Tv

Ug

1.0

0.2

g

g

1.0

1.0

Tv

g

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Building envelope

5.3 Facade orientation As discussed in the previous chapter, different parts of a building have different solar access, and that requires façades with different orientations to be treated differently in order to achieve optimal environmental behaviour.

For example, north-facing windows generally have good access to daylight and little direct solar gain; southfacing window receive direct solar gains both in winter, when it can be beneficial in order to reduce the heating loads, and in summer, when it is problematic as it adds to the cooling loads. East facing windows receive low angle solar radiation, leading to risks of glare, while west-facing windows present both risks of glare and excessive solar heat gains when outdoor air temperatures are high, resulting in very critical conditions (summer afternoon scenario).

The impact of different facade orientations on ADIABATIC WALLS energy demand can be assessed by means of energy ADIABATIC FLOORS/CEILINGS simulations. A 8.1m wide, 6m deep and 3.3m high office room was modelled, to represent a slice of the reference office building.

The room bounding surfaces (internal walls, ceiling, floor) were considered adiabatic, to exaggerate and highlight the contribution of the external facade in full.

The curtain walling facade includes glazed elements up to ceiling height and spandrel panels up to sill level of 0.9m (WWR=73%), as shown in Figure 38.

Thermal simulations show (Figure 39) that if a south facing room is taken as a reference, different orientations result in a trend towards a progressive increase of lighting demand (up to 127% for the north orientation) and a rapid decrease of cooling demand (down to 45% for the north orientation).

kWh/m2 y

HEATING

GLAZING Uw=1, g=0.5, Tv=0.6 WALL / SPANDREL U=0.4

Figure 38. Test room used for assessing the effect of orientation on energy demands

COOLING

LIGHTING

55 102%

50

104%

110% 45

127%

113%

121%

40

99%

90%

80% 55%

30 45% 25 108%

70%

REFERENCE

35

20

121%

107%

104%

51%

105%

102%

102%

107%

Figure 39. Variation in the test room’s energy demands (heating, cooling and lighting) for different orientations, London

NORTH-EAST

EAST

SOUTH-EAST

SOUTH

SOUTH-WEST

0

WEST

5

NORTH

10

NORTH-WEST

15

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5.4 Fenestration and window-to-wall ratio An important metric for the characteristics of a building’s façade’s is the window-to-wall ratio (WWR), that is the proportion of glazed to opaque area. This ratio is a significant contributor to a façade’s heat loss, solar heat gain, daylight levels. Because the thermal resistance of even a well-insulated glazed facade is typically lower than that of an opaque facade, higher WWRs normally result in greater energy consumption.

Following on the previous section, having fixed the dimensions of the ‘dummy’ room, the internal loads (from occupancy, equipment and lighting) and the thermal properties of the building envelope (Figure 38) the passive balance between heat gains and losses that derive from the progressive reduction of WWR can be assessed.

The chart shows how the reduction of WWR results in a significant decrease of solar heat gains, as well as and increase in heat losses, which both contribute to an overall increase of energy consumption.

AH1

AV0

WWR 73%

AH3

AV1

WWR 64%

WWR 48%

AV4

WWR 45%

WWR 27%

Figure 40. Schematic representation of alternative options for reducing the WWR

SOUTH-EAST

A0_73%

AH1_64%

AV1_48%

AH3_45%

AV4_27%

SOUTH

A0_73%

AH1_64%

AV1_48%

AH3_45%

AV4_27%

Solar Heat Gains (kWh/m2)

8 7 6 5 4 3 2 1

Heat Losses (kWh/m2)

0

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

-1 -2 -3 -4 -5 -6 A0_73%

AH1_64%

AV1_48%

AH3_45%

AV4_27%

Figure 41. Solar gains and heat losses for different WWR, for south-east (solid lines) and south (dashed) orientations, London

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Building envelope

However it is interesting to note how the difference in solar heat gains during the summer is significantly higher than the increase of heat losses in winter, and this is true for both Helsinki (Figure 41) and London (Figure 42).

Hence, rather than depending on climatic conditions, this is due to the fact that the performance of the test room, which is modelled with adiabatic boundary surfaces, is mainly influenced by that of its glazed facade.

With a low U-value and a moderately good solar factor, solar heat gains overweight heat losses, even for cold climate zones. While the values here presented show a qualitative pattern and they are not representative of the reference buildingâ&#x20AC;&#x2122;s performance, these trends highlight an importance issue: careful design should consider the consequences of introducing triple and quadruple glazing without solar control, as solar heat gains might add to already high internal gains (which are typical for office buildings), leading to overheating or significant increase of cooling demands.

SOUTH-EAST

A0_73%

AH1_64%

AV1_48%

AH3_45%

AV4_27%

SOUTH

A0_73%

AH1_64%

AV1_48%

AH3_45%

AV4_27%

9

Solar Heat Gains (kWh/m2)

8 7 6 5 4 3 2 1

Heat Losses (kWh/m2)

0

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

-1 -2 -3 -4 -5 -6 A0_73%

AH1_64%

AV1_48%

AH3_45%

AV4_27%

Figure 42.â&#x20AC;&#x192; Solar gains and heat losses for different WWR, for south-east (solid lines) and south (dashed) orientations, Helsinki

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5.5 Solar shading Solar shading devices are a very effective passive design strategy to control solar heat gain and achieve positive influence on energy performance. Shading devices are normally divided into three main types: internal, intermediate or integral and external.

Internal shading

Internal shading, i.e. blinds, have a very low installation cost and are adopted largely as a simple tool for solar control in office buildings. However they offer very low sun protection, allowing ca. 50% of solar gain inside the room.

Mid-pane blinds

Mid-pane blinds are more effective, transmitting on average only 30% of solar gain. They present increased initial costs, but require relatively low maintenance and offer performances that are constantly increasing thanks to a receptive market.

External shading

Of all shading devices external devices are the most effective at controlling solar heat gains, as they intercept the incident solar radiation before it reaches the façade of the building. The size and shape of the shading elements vary according to the latitude and orientation of the building. As a general rule of thumb southfacing façades are best protected with horizontal elements whilst east and west façades benefit from the use of vertical elements.

The several solutions for external shading can be classified into four main types, most of which are shown in Figure 43 below: 1. Overhang, horizontal canopy, window reveals; 2. Horizontal louvres; 3. Vertical louvres; 4. External curtain / roller blinds.

Figure 43. External shading alternatives

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Building envelope

5.5.1. Solar shading for the reference building Horizontal geometries

The different shading systems and their impact in terms of energy use are illustrated in Figure 44. The energy demand for cooling is clearly most affected and this reduces by 64% from the base case to SH3 and SH4 geometries. Because of a slight increase of lighting energy, due to lower daylight levels, the total energy use reduces to approximately 74% of the base case for the more effective shading systems.

A0

A0 SH1

AH3

A0 SH2

AH3 SH1

LIGHTING

NAME

TYPE

A0 A0 SH1 A0 SH2 A0 SH3 A0 SH4 A0 SH5

Unshaded - WWR 73% Horizontal shading H. shading + fixed louvres (top pane) H. shading + moveable louvres (top pane) H. shading + moveable louvres (top pane) Multiple horizontal shading

AH3 AH3 SH1 AH3 SH2

Unshaded - WWR 45% Horizontal shading Horizontal shading - deeper

A0 SH3

A0 SH4

A0 SH5

AH3 SH2

VENTILATION

COOLING

HEATING

50 45 40 35 30 25 20 15 10 5 0 A0

A0 SH1

A0 SH2

A0 SH3

A0 SH4

A0 SH5

A3

A3 SH1

A3 SH2

Figure 44. Annual energy demands (kWh/m2/year) for rooms with horizontal shading for south-east orientation

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External shading - vertical geometries

The different vertical shading systems and their resulting energy use are illustrated in Figure 45. Again, the energy demand for cooling reduces significantly as a result of shading, achieving a 54% reduction from the base case for WWR of 73% (option A0), and 40% reduction from base case for WWR of 48% (option AV1). For the more effective shading systems, the overall energy use reduces to 82% of the base case for option A0 and 89% for option AV1, where the moderate reduction in cooling demand is partly compensated by the increased demand for artificial lighting.

Although simulations show that the best energy performance is achieved with the smallest window-to-wall ratios, recent developments in nano-technologies applied to glazing allow increasingly lower U-values and G-values to be achieved, while maintaining acceptable visible light transmission. Due to this, areas of glazing can be extended without serious consequences on the building energy demand.

A0

A0 SV1

A0 SV2

AV1

AV1 SV1

AV1 SV2

LIGHTING

NAME

TYPE

A0 A0 SV1 A0 SV2 A0 SV3 A0 SV4 A0 SV5

Unshaded - WWR 73% Vertical shading - 1m centres Vertical shading - 0.75m centres V. tilted shading - 0.5m centres V. tilted shading - 0.75m centres Vert. tilted shading - 1m centres

AV1 AV1 SV1 AV1 SV2

Unshaded - WWR 48% Vertical shading - window reveals Vertical shading - 1.5m centres

AV2 AV2 SV1

Unshaded - WWR 48% Vertical shading - window reveals Vertical shading - tilted window reveals

AV2 SV2

A0 SV3

A0 SV4

AV2

VENTILATION

51

A0 SV5

AV2 SV1

COOLING

AV2 SV2

HEATING

50 45 40 35 30 25 20 15 10 5 0

A0

A0 SV1

A0 SV2

A0 SV3

A0 SV4

A0 SV5

AV1 AV1 SV1

AV1 SV2

AV2 AV2 SV1

Figure 45.â&#x20AC;&#x192; Annual energy demands (kWh/m2/year) for rooms with vertical shading for south-east orientation

AV2 SV2

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6 HVAC STRATEGIES AND ON-SITE RENEWABLE ENERGY GENERATION

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HVAC strategies and on-site renewable energy generation

6.1 Baseline and nearly zero-energy HVAC systems overview 6.1.1. Baseline case - system diagram The energy system for the baseline case represents a typical, yet fairly energy efficient solution for office buildings in Northern and Central Europe, and it is illustrated in Figure 46.

The main heating energy supply has been identified as district heating, while cooling runs on electricity from the grid. The heating and cooling systems are based on radiant ceiling panels. The building is equipped with mechanical ventilation with heat recovery, with air handling units (AHU) supplying fresh air to meet standard indoor comfort conditions.

Space heating and domestic hot water (DHW) are supplied by district heating, while conventional electrical chillers are used for space cooling, both through the radiant panels and the supply of cool fresh air.

As mentioned, the building relies entirely on the electricity grid to match its electricity demand.

6.1.2. Nearly Zero Energy case - system diagram Compared to the baseline system, three sources for on-site renewable energy generation are introduced: • Photovoltaic panels, located on the roof or integrated with the façade, generate electricity; • Energy piles are used to exchange heat with the ground, with ground-source heat pumps (GSHP) providing heating and cooling energy to meet the building’s demands; • Solar thermal collectors provide heating energy that meets the demands for domestic hot water (DHW) plus they serve as a backup energy source (through the heat buffer tanks) for space heating.

ENERGY SUPPLY

ENERGY DEMAND

kWh/m2

kWh/m2

District Heating

DHW kWh/m2

Radiant Panels

Space heating kWh/m2

AHU

Space cooling kWh/m2

Chiller

Supply air kWh/m2

Lighting kWh/m2

Electricity Grid

Figure 46. System diagram for the base line design

kWh/m2

Equipment

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS ENERGY SUPPLY

55 ENERGY DEMAND

The electricity generated on-site by the PV system is mainly used within the building and a surplus or a lack of PV generation, which are likely to occur in summer and winter respectively, are absorbed by the external grid, whichkWh/m is effectively used as a ‘buffer’. The PV system is sized to achieve an annual “nearly-zero” balance kWh/m between energy demand and generation.

2

2

District Heating

DHW

The key elements for achieving high levels of energy efficiency is the heat pump, which are fed by PV-generated electricity. As the efficiency of the heat pumps increases notably if an adequate heat source is available,kWh/m the integration with energy piles is of capital importance.

Radiant Panels Space heating 2

As it is discussed in the next chapter, during the heating season, energy piles extract heat from the ground kWh/m to feed the heat pumps, which is equivalent to ‘storing cold’ in the ground. That ‘stored cold’ is important Space cooling for the system balance, as it would then serve as a source of free AHUground cooling over the cooling season Additionally, the cooling of the building results in ‘recharging’ the ground for the next heating season, with different intensity and duration depending on the geological characteristics of the building site, so thatkWh/m a Chiller Supply air seasonal buffering is achieved. The system offers optimal benefits if the differences between the room operative temperature and heating/cooling plant running temperature are low; as such, an integrated radiant system is kWh/m the best choice.

2

2

2

Lighting

An AHU is installed to pre-condition the supply air for heating and cooling. An electrical chiller is provided to support the free ground cooling during the summer period, in order to ensure the system can match peaks in kWh/m kWh/m cooling demand. Buffer tanks for DHW, heating and cooling are implemented for storing heat/cold for a few Electricity Grid Equipment days, to help matching peak loads and in order to maximise the efficiency of the different system components.

2

2

ENERGY SUPPLY

ON-SITE RENEWABLE ENERGY GENERATION

ENERGY DEMAND

kWh/m

2

Photovoltaic

Energy Piles

Solar thermal

kWh/m2

DHW Buffer Tank

Heat Pumps

Heating Buffer Tank

DHW kWh/m2

Radiant Panels

Space heating kWh/m2

Cooling Buffer Tank Chiller

Space cooling AHU kWh/m2

Supply air kWh/m2

Lighting kWh/m2

Electricity Grid

Figure 47. System diagram for the nearly-zero energy case

kWh/m2

Equipment

56

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HVAC strategies and on-site renewable energy generation

6.2 On-site renewables: energy piles and ground source heat pumps 6.2.1. Description of technology The most important role of the steel pile is the loadbearing capacity, since the type of the pile is chosen based on the ground properties and the building loads. The heat demand of the building determines the design of the pipes placed inside the steel pile (e.g. U or double U setting).

In winter time, heat energy stored in the ground can be used for heating and in summer time low temperature of soil can be utilized for cooling.

The energy pile system is based on steel piles with additional heat collector pipes installed into the piles, connecting pipes via manifolds to heat pump, heat-transfer liquid and heating-cooling distribution system. It is also possible to utilize energy piles without a heat pump by simple circulation pump especially in cooling periods (free ground cooling).

Normally heat-collecting pipes are made from high density polyethylene (PE) and the diameter usually varies from 20 - 40 mm. A typical collector pipe in steel energy piles has been PE-Xa 25x2,3. Steel pile diameters used in buildings normally enable only one or two loops with U-shape collecting system.

After installation, check valves are connected into the both ends of all loops and pipes are pressurized to secure the tightness.

Figure 49. Concept diagram of integration of energy pile with heating/cooling system (left) and concept scheme of an energy pile (right).

6.2.2. Working principle Collecting pipes are connected to manifolds from where it is possible to control desired number of energy piles. From manifolds, the heat-transfer liquid flows via ring mains to heat pump and then back to the piles. A water - ethanol mixture is most common heat-transfer liquid used in energy piles. In the PE pipes, heat carrier fluids circulate for energy extraction in winter and for energy storage in summer. The heat content of the fluid is extracted by heat pumps since the temperature of the fluid is lower than the temperature of the soil, in addition during the coldest days this value can reach 0 °C. The thermal conductivity of the soil is the most important characteristic factor, the extractable energy is directly proportional to its thermal conductivity. Compact rocks have a higher thermal conductivity than loose sediments, and in addition the thermal conductivity below groundwater table is higher than above. In most cases, the thermal conductivity of a location is known before designing the ‘system’.

The steel pile and thermal grout can increase the efficiency of the heat extraction and storage, since the temperature decrease is lower for the same energy extraction. The dimensions and type of steel pipes and PE pipes have also significant effect on the extractable energy per pipe length.

Figure 48. Manifold collection of pipes from the energy piles

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

57

Double U pipes have approximately 20 % higher efficiency with than single U pipes, but the cost is approximately double. This effect derives from the fact that near the PE pipes, the temperature decreases rapidly and the horizontal heat flow cannot supply the extraction rate.

In double U systems, the zones closer to the pipes are cooled down rapidly but the size of these zones are not higher than in the case of single U type systems.

6.2.3. Sizing and configuration of piles The effect of the steel pile size and pipe configuration on annual heat peak power of a single 20m pile in a Central-European climate is shown in Figure 50. Analysis is based on typical heat demand distribution of typical office building with yearly utilization hours of 2069 h. The figure show peak power per m length of pile and total power of the 20m pile. Yearly heating energy yield may be determined by multiplying the maximum power with 2069 h. In the following figures, a single pile of 170x10 with double U 25x2,3 collector is shown as “reference case”.

If the temperature balance of the soil is kept stable in a long run by suitable ratio of extracted and recharged heat energy, the influence of the energy pile field and distance between the piles is negligible on the heating power in the studied cases, as shown in the following figure. In this case, the heating energy extracted and recharged are equal, but this not a requirement of the system.

It should be noted that, especially for large and dense energy pile fields, the long term behaviour can decrease dramatically without soil charging during the summer. The difference the between short term (3 years) and long term (50 years) performance for the case without any soil charging can be as high as 30% for large pile groups, but is about 10% for smaller pile groups.

50 45 40

heat per m

900

extracted heat (total)

reference

reference

600

30 450

25 20

300

15 10

150

5 0

0 single U 25x2,3 pile 170-10

single U 25x2,3 pile 170-10

2U 25x2,3 pile 170-10

2U 25x2,3 pile 220-10

2U 25x2,3 pile 400-12,5

single U 25x2,3 pile 115-6,3

Figure 50. Extracted heat for different configuration of pipes and piles for heating and cooling. Length of the single pile 20m

70 ambient air 60

W/m

50 40 30 20

base plate

W

W/m

35

750

20

58

15 WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS 10 HVAC strategies and on-site renewable energy generation

300 150

5 0

0

The models presented pile Ufield. The single U previously singlehave U not taken 2 Uinto account 2the U building above 2 U the energy single building improves the heating25x2,3 energy extraction because heat losses to ambient air are eliminated 25x2,3 25x2,3 25x2,3 25x2,3 25x2,3 and pile 170-10 pile the 170-10 220-10 furthermore, heat losses from buildingpile into170-10 the soil willpile also improve pile the 400-12,5 heat balancepile of 115-6,3 the soil. The following figure gives an example of the influence of the building above to the different sizes of energy pile fields. In these cases, the heating energy extraction and recharging was in balance.

70 ambient air

base plate

60

W/m

50 40 30 20 10 0 7 boreholes 6m distance

19 boreholes 6m distance

100 boreholes 6m distance

Figure 51. Effect of building above the energy pile field instead of ambient air Results as a function of the number of energy piles and running time – only heating, pile distance 6m

6.2.4. System requirements Achieving a proper working energy pile system requires careful planning of the whole building energy system.

Firstly, the long term behaviour is optimised depending on a suitable ratio between extracted and recharged heating energy. If the annual cooling energy demand of the building is very low, soil charging can be arranged for example by solar heat collectors or by utilizing heat energy of the ventilation waste heat during the summer.

If the heating energy extraction is the main purpose of the energy pile system, the ratio between recharged and extracted heat energy may be as large as possible (even equal). For cases where energy pile field is utilized for heating and free ground cooling, control the long term soil temperature development is required by changing the am ratio.

System temperature levels should be designed in such a way, that the outlet temperature is not lower than 0 °C in order to avoid possible problems in the structural behaviour of the foundations. In order to maximize performance of the ground energy usage, the heating and cooling systems should be designed based on low exergy principle, meaning that heating should be realized with low temperature systems and cooling with high temperature systems. For example, radiant panels usually fulfil these requirements.

Heat pumps can work in reverse mode in the summer for cooling purposes, or alternatively different chillers for cooling purposes that also utilize low ground temperatures by condensing. Cooling energy can be extracted also by so called ‘free cooling’ when fluid is circulated only with circulation pumps to the cooling devices without compressors. If the free ground cooling energy is maximized, it might be reasonable to use separate energy pile fields for cooling purposes while another field will be charged by solar heat in the spring.

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

59

6.2.5. Design examples The extractable power is based on three different parameters: the maximum temperature difference between soil and fluid which is allowed in the system, the total length of the energy piles and the energy demand in heating and cooling phase. In the following tables, the most important design values are shown with average thermal conductivity of 1.9 W/(mK) and a maximum temperature difference of ΔT=11 °C corresponding Central-European conditions, based on initial natural soil temperature of 11 °C and minimum fluid temperature of 0 °C. The tabulated values are based on the modelled utilization hours (2069h /year) for an office building. If the maximum temperature difference is lower, the specific power values should decrease proportionally. Values are based on the assumption that soil charging during summer is equal to heating energy extracted during winter and without influence of the building above. Values are valid for any size of energy pile field where the minimum distance between piles is 4m.

Table 10. Recommended design values for the reference building, ΔT=11 °C

Steel pile / collector

115x6,3

170x10

170x10

400x12,5

U-25x2,3

U-25x2,3

2U-25x2,3

2U-25,3

Specific power

30 W/m

31 W/m

39 W/m

43 W/m

Yearly energy yield

62 kWh/m

64 kWh/m

81 kWh/m

89 kWh/m

If the ground thermal conductivity is 1.1 W/(mK), these values should be reduced by a factor of 0.85. For Nordic conditions, ΔT=7 °C may be used.

The heat injection in the summer period is a key-point in the regeneration of the ‘system’. In this way, the temperature of the sub-surface near the energy piles becomes higher than the original temperature, moreover, the continuous energy loss of the subsurface is prevented. The energy balance of the ground is based on not only the climate, but the demands of the building. Furthermore, the extra heat (from solar energy) in summer may be stored in the ground to be used as heating in the winter.

Based on the models, an energy pile 170/10 of 20 m length and with double U collectors can extract about 800 W if the maximum temperature difference is about 11 °C in non-continuous operations. Considering 40 W/m (rounded output) average specific power and energy pile field (square mesh) with distance between the piles 4 m to 7.5 m, and three different energy pile length, the extractable heating energy could be calculated to building area.

The presented results are indicative values, and the general effects on the performance are explained above.

Nevertheless an accurate design of each building project with ground heat exchangers in combination with heat pump and cooling (free ground cooling and/or chiller) is essential.

Table 11. Power values per building footing size, ql=39 W/m, ΔT=11 °C*

Pile field,

Pile field,

Pile field,

d= 4m

d= 6m

d= 7.5m

400 W

25.0 W/m2

11.11 W/m2

7.11 W/m2

15 m

600 W

37.5 W/m2

16.67 W/m2

10.67 W/m2

20 m

800 W

50.0 W/m2

22.22 W/m2

14.22 W/m2

Length of pile

Power / pile

10 m

60

WP 6.4 DESIGN GUIDE FOR STEEL INTENSIVE NEARLY-ZERO ENERGY OFFICE BUILDINGS

HVAC strategies and on-site renewable energy generation

6.3 On-site renewables: solar thermal 6.3.1. Description of technology Solar thermal systems collect and store heat from solar radiation. Heat is collected by roof-top panels and then transferred via a dedicated pipe and pumped to a water tank. From the water tank, the heated water can be used for Domestic Hot Water (DHW) and for space heating, when the heating system is water-based (radiant ceilings or floors). Water tanks are designed differently for the hot water use.

6.3.2. Advantages and disadvantages Solar thermal systems operate best in low temperatures, and as such they are very advantageous for water preheating or as a support for the main heating system, such as electrical immersion heater, boiler (gas, oil, wood) or ground/air heat pump.

The availability of solar energy is not consistent on a daily or monthly basis, and as such, providing sufficient storage capacity is essential for making this technology viable. Similarly, the annual energy yield is limited to the available cumulative amount of sunshine hours, a limitation that does not exist for other types of heating energy sources.

On the positive side, solar thermal pumps consume little electricity as they usually have input/output energy ratio of 1:3, whereas solar has normally less than 1:20 ratio.

6.3.3. Water tanks Solar thermal systems are usually connected to the heat exchange circuit of the water tank, or alternatively to an external heat exchanger. As already mentioned, the structure of the water tank determines the possible use of the heated water.

Two main types of water tanks are available: 1. single-compartment for DHW; 2. double compartment tank for DHW and space heating.

Single compartment water tanks are used for domestic hot water. Space heating is then provided with a different system, such as by direct electric heating, or by a small heating circulation tank in a separate boiler, which goes direct to the space heating system, not via the water tank. The required size of the tank depends on hot water consumption, in detached houses an appropriate size is from 200 to 500 litres depending on the number of residents.

Figure 52. Single (left) and double (right) compartment water tanks for DHW and space heating

Double compartment (i.e. Hybrid) water tanks are used for both DHW and space heating. They are built as a “tank within a tank”, as shown in Figure 52, with the outer tank for DHW and the inner one for space heating.

The solar circuit is connected to the outer tank, which then heats up the inner tank. Hybrid water tanks are usually larger than single compartment ones, and typically 700-1000 litre tanks are needed for a system serving a detached house.

Hybrid water tanks are equipped with a second heat exchange circuit, used for any other water-based heating sources, and a separate socket for an electrical immersion heater located within the water tanks.

ZEMUSIC ZERO ENERGY SOLUTIONS FOR MULTI-USE STEEL INTENSIVE COMMERCIAL BUILDINGS

6.3.4. Solar Thermal Solutions Many solar thermal systems are nowadays available, offering different collector technology, efficiency and component solutions.

Classic Solar is a fully integrated solution for Ruukki Classic steel standing seam roof. It is available with collector field size unit of 4 m², which can be installed in series. The system is illustrated in Figure 53.

61

Collector panels

Pump station with control unit

Alternative heat source

Expansion vessel

Heat transfer pipe Storage tank

Figure 53. Solar thermal system with DHW from Ruukki

6.3.5. Selecting and sizing solar thermal solutions The solar system is selected or designed according to the planned use and energy output needs.

The selection of solar thermal solutions depends on a number of factors, such as the type of building, the DHW and heating energy demand, the size of solar collectors and the presence of a heat transfer system.

The application area of solar collectors can be associated with their size, as collectors of up to 8 m² normally supply DHW for a detached house, and collectors of 10–14 m² are used to supply both DHW and space heating water for the same building type. Collector larger than 16 m² are normally needed for larger non-domestic buildings (e.g. hotels, schools, offices) or for some process applications in agriculture or manufacturing.

The sizing of solar collectors for DHW is generally a simple process, as the quantity of daily DHW demand and the roof orientation (which determines the absorption capacity) are the only parameters that are needed. In borderline cases however, the yield and the operating temperature of the system might need to be calculated with computer modelling.

In non-residential buildings with a low DHW use, solar collectors may be integrated with space heating systems.

The integration of solar panels with ground source heating (e.g. energy piles) increases the efficiency of the piles: by recharging the ground with solar heating energy during the summer, when space heating is not needed, the medium and long term performance of the ground source heating system can be significantly improved. As the recharging of the ground is achieved with some relatively low temperatures (if compared to DHW for instance), the annual efficiency of the solar heat system increases to 85%.

Collector sizing is based on hot water need and placement and orientation of collector field. The ability of collectors to absorb sunlight depends on parameters like azimuth, inclination and overshadowing.

In addition to these factors, the heat transmission and storage losses have to be considered. In this respect, collectors should be located as close as possible to the water tanks in order to minimise heat transfer losses.

The main limitation of solar thermal systems is the operating temperature, as the vector fluid should not exceed 100 °C for long periods of time, to avoid vaporizing, which would prevent its circulation. Occasional overheating is acceptable, as an expansion vessel can accommodate the vapour until the liquid returns into its optimal operating temperatures.

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6.4 On-site renewables: solar photovoltaic 6.4.1. Solar potential: Photovoltaic Geographical Information System (PVGIS) A solar radiation database was developed from climatological data, and made available in the European Solar Radiation Atlas. It is therefore possible to estimate solar irradiation [Wh/m2] on horizontal or inclined surfaces for most European locations on a monthly and yearly basis.

Figure 54. Photovoltaic solar electricity potential in European countries PVGIS © EU2008 * Global irradiation: yearly sum of global irradiation incident on optimally-inclined south-oriented photovoltaic modules ** Solar electricity: yearly sum of solar electricity generated by optimally-inclined 1 kWp system with a performance ratio of 0.75

6.4.2. PV generation: effect of tilt and orientation for different locations The Solar electricity utility application allows to calculate the monthly and yearly potential electricity generation E [kWh] of a PV configuration with defined panel inclination (or tilt) and orientation, based on the peak power installed, the system performance ratio and the monthly or yearly average of daily global irradiation of a PV configuration: E = 365 Pk rp Hh,I Where Pk (kW) is the peak power installed rp is the system performance ratio (typical value for C-Si roof mounted system is 0.75) Hh,i is the monthly or yearly average of daily global irradiation on the surface where the PV is installed.

The performance characteristics of PV relative to the orientation are presented in the next page for the three chosen locations. It can be seen that the specific annual yield (annual yield/peak power installed) is fairly similar for Helsinki and London, while it increases dramatically for Bucharest. The value also appears to be relatively insensitive to the tilt angle and orientation of up to 30° from the optimum.

70° 80° 62% 67% 71% 74% 77% 80% 81% 82% 83% 83% 83% 82% 81% 80% 77% 74% 71% 67% 63% 60% 63% 69%SOLUTIONS 71% 72% FOR 73%MULTI-USE 74% 74% STEEL 74% INTENSIVE 73% 73% COMMERCIAL 71% 69% 67% 63% 60% 56% 90° 56% ZEMUSIC ZERO66% ENERGY BUILDINGS

WEST map for SOUTH-WEST SOUTH-EAST EAST Table 12. Efficiency PV potential: specific annual SOUTH yield (kWh/kWp) for different orientations and tilt, Helsinki TILT

TILT 0° 87% 90° 10° 87% 0° 775 20° 85% 10° 769 30° 83% 20° 756 40° 80% 30° 750 50° 76% 40° 731 60° 71% 50° 700 70° 65% 60° 663 80° 58% 70° 616 90° 50% 80° 558

80° WEST 87% 80° 88% 775 88% 781 86% 781 84% 781 80% 769 75% 744 69% 713 62% 663 54% 604

493

536

90°

90°

70°

30°

20°

87% 70° 88% 775 89% 794 88% 806 87% 813 84% 806 79% 788 73% 750 66% 706 58% 644

60° 50° 40° SOUTH-WEST 87% 87% 87% 60° 50° 40° 90% 91% 91% 775 775 775 91% 93% 95% 806 813 825 91% 94% 96% 831 850 863 90% 93% 96% 844 869 888 87% 90% 93% 838 869 894 83% 86% 88% 825 856 881 77% 80% 83% 794 825 850 69% 72% 75% 744 775 800 61% 64% 66% 681 713 738

87% 30° 92% 775 96% 831 97% 875 97% 900 95% 913 91% 900 85% 869 77% 825 68% 756

87% 20° 93% 775 96% 838 98% 888 99% 913 96% 925 93% 913 87% 888 79% 838 69% 769

574

608

675

688

638

656

10°

0° 10° SOUTH 87% 87% 87% 10° 0° 10° 93% 93% 93% 775 775 775 97% 97% 97% 838 844 844 99% 100% 99% 894 894 894 100% 100% 100% 919 925 925 97% 98% 97% 931 938 931 94% 94% 94% 925 925 925 88% 88% 88% 894 900 894 80% 80% 80% 844 850 850 70% 70% 70% 775 781 781

694

694

694

20°

30°

87% 20° 93% 775 96% 838 98% 888 99% 919 96% 925 93% 919 87% 888 79% 838 69% 775

87% 30° 92% 775 96% 831 97% 875 97% 906 95% 913 91% 906 85% 875 77% 825 68% 763

40° 50° 60° SOUTH-EAST 87% 87% 87% 40° 50° 60° 91% 91% 89% 775 775 775 95% 93% 91% 825 819 806 96% 94% 91% 869 850 831 96% 93% 90% 888 869 844 93% 90% 87% 894 875 844 88% 86% 82% 888 863 831 83% 80% 76% 856 831 800 75% 72% 69% 806 781 750 66% 64% 61% 744 719 688

688

681

663

644

615

70°

90

87% 70° 88% 775 89% 794 88% 813 87% 819 84% 813 79% 794 73% 763 66% 713 58% 656

80° EAST 87% 80° 88% 775 87% 781 86% 788 83% 788 80% 775 75% 756 69% 719 62% 669 54% 613

87% 90 86% 775 85% 769 83% 763 80% 756 76% 738 71% 713 64% 675 58% 625 50% 567

583

544

502

WEST map for SOUTH-WEST SOUTH-EAST EAST Table 13. Efficiency PV potential: specific annual SOUTH yield (kWh/kWp) for different orientations and tilt, London TILT

90° TILT 0° 88% 90° 10° 87% 0° 813 20° 86% 10° 806 30° 84% 20° 788 40° 81% 30° 769 50° 77% 40° 738 60° 72% 50° 700 70° 66% 60° 650 80° 59% 70° 589 90° 52% 80° 523 90°

451

80° WEST 88% 80° 88% 813 88% 819 87% 813 85% 800 81% 775 76% 738 70% 694 63% 631 55% 565 490

70°

30°

20°

88% 70° 90% 813 90% 831 90% 831 88% 825 85% 806 80% 775 74% 731 67% 675 58% 604

60° 50° 40° SOUTH-WEST 88% 88% 88% 60° 50° 40° 91% 92% 92% 813 813 813 92% 94% 95% 838 850 856 92% 95% 97% 856 869 888 91% 93% 96% 856 875 900 88% 91% 93% 838 869 894 84% 86% 89% 813 844 869 77% 80% 82% 769 800 831 70% 72% 74% 713 744 775 61% 63% 65% 644 675 700

88% 30° 93% 813 97% 863 98% 900 97% 913 95% 913 91% 894 84% 856 76% 800 66% 725

88% 20° 93% 813 97% 869 99% 906 99% 925 97% 925 92% 906 85% 869 76% 813 67% 744

527

561

638

650

591

617

10°

0° 10° SOUTH 88% 88% 88% 10° 0° 10° 93% 94% 93% 813 813 813 98% 98% 98% 875 875 875 100% 100% 100% 913 913 913 100% 100% 100% 931 938 931 97% 97% 97% 938 938 938 93% 93% 93% 919 919 919 86% 86% 86% 881 888 881 77% 77% 77% 825 831 825 67% 67% 67% 750 756 750 656

663

663

20°

30°

88% 20° 93% 813 97% 869 99% 906 99% 925 97% 925 92% 906 86% 875 77% 819 67% 744

88% 30° 93% 813 97% 863 98% 900 98% 913 95% 913 91% 894 84% 856 76% 800 67% 731

40° 50° 60° SOUTH-EAST 88% 88% 88% 40° 50° 60° 92% 92% 91% 813 813 813 95% 94% 92% 856 850 844 97% 95% 93% 888 875 856 96% 94% 92% 900 881 856 93% 92% 89% 894 869 844 90% 87% 84% 875 844 813 83% 81% 78% 831 806 769 75% 73% 71% 775 750 713 65% 64% 62% 706 675 644

656

638

620

594

564

70°

90

88% 70° 90% 813 91% 831 90% 838 89% 831 86% 813 81% 781 75% 731 67% 675 59% 608

80° EAST 88% 80° 88% 813 88% 819 88% 813 85% 800 82% 775 77% 744 71% 694 64% 638 56% 568

88% 90 88% 813 86% 806 84% 794 82% 769 78% 738 73% 700 67% 650 60% 529 53% 526

530

493

453

Table 14. Efficiency map for PV potential: specific annual yield (kWh/kWp) for different orientations and tilt, Bucharest TILT 0°

WEST 90°

80°

SOUTH-WEST 70°

60°

50°

40°

SOUTH 30°

20°

10°

0°

SOUTH-EAST 10°

20°

30°

40°

50°

60°

EAST 70°

80°

90

1088 1088 1088 1088 1088 1088 1088 1088 1088 1088 1088 1088 1088 1088 1088 1088 1088 1088 1088

10° 1075 1094 1106 1119 1131 1144 1150 1156 1163 1163 1163 1163 1156 1150 1138 1125 1113 1100 1081 20° 1050 1081 1106 1131 1156 1175 1194 1206 1213 1213 1213 1206 1200 1188 1169 1144 1119 1094 1063 30° 1019 1056 1094 1131 1163 1188 1206 1225 1238 1238 1238 1231 1219 1200 1175 1150 1113 1081 1038 40°

975 1025 1069 1113 1144 1175 1200 1219 1231 1238 1238 1231 1213 1194 1163 1131 1094 1050 1000

50°

925

975 1025 1069 1106 1144 1169 1188 1206 1213 1206 1200 1188 1163 1131 1094 1050 1006 950

60°

856

913

963 1013 1050 1088 1113 1138 1150 1156 1156 1150 1131 1106 1075 1038 994

944

888

70°

781

838

888

931

975 1006 1038 1056 1069 1075 1075 1069 1056 1031 1000 963

919

869

813

80°

694

750

800

838

881

906

931

950

963

969

969

963

950

931

906

869

825

781

725

90°

599

650

694

731

763

788

813

819

825

831

831

831

825

813

788

763

725

681

631

63

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HVAC strategies and on-site renewable energy generation

6.4.3. Strategies for integrating PV Two different strategies for integrating PV cells into the building envelope were employed depending on the architectural solutions that may be considered to be relevant to different market conditions. In all cases, inclined PV panels were placed on as much as the roof area as feasible, as this is the primary source of electricity generation.

Helsinki

In Helsinki, the PV cells were integrated into the metallic facade system on the south-east and south-west facing spandrel panels, as well as on the flank walls which do not have windows, as illustrated in Figure 55. Table 15 presents the electricity generation on the roof and façade, which leads to a yearly generation with respect to the building’s Net Floor Area (NFA). The total generation is 18.53 kWh/m2 NFA.

PV on ROOF Orientation Tilt PV Area PV yield (kWh/m2/y) Yearly Generation (kWh/y)

S 35° 408 147.4 60222

PV on South-East façade Orientation Tilt PV Area PV yield (kWh/m2/y) Yearly Generation (kWh/y)

SE 90° 458 102.8

Figure 55. Location of PV panels on different parts of the reference building

50998

Table 15. Areas, PV yield per unit of surface area and yearly energy generation for different PV systems on the building - Helsinki

PV on South-West façade Orientation Tilt PV Area PV yield (kWh/m2/y) Yearly Generation (kWh/y)

SW 90° 613 102.4 62970

PV location

PV yield PV Area Area % (m2) (m2) area (kWh/ m2/y)

Roof SE Façade cladding SW Façade cladding

1036 1156 1130

408 458 613

39% 43% 54%

Total PV energy (kWh/y)

Total PV energy (kWh/ m2,NFA/y)

147.4 102.8 102.4

60222 50998 62970

6.41 5.43 6.70

TOTAL

174190

18.53

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London

In London, a different strategy was adopted because of the market preference for highly glazed curtain walling systems. In this case, a vertically-orientated shading system is used on both the south-east and south-west façades and the PV cells are bonded to the shading system, which are in their optimum orientation. In addition, PV is placed on the flank walls which do not have windows, as illustrated in Figure 56. Table 16 presents the electricity generation on the façade, shading and roof, which is converted to yearly generation with respect to the building’s Net Floor Area (NFA). The total generation is 12.35 kWh/m2 NFA.

PV on ROOF Orientation Tilt PV Area PV yield (kWh/m2/y) Yearly Generation (kWh/y)

S 35° 408 148.2 60525

PV on South-West facade Orientation Tilt PV Area PV yield (kWh/m2/y) Yearly Generation (kWh/y)

SW 90° 306 96.1 29400

Figure 56. Location of PV panels on different parts of the reference building

PV on SE ext. shading Table 16. Areas, PV yield per unit of surface area and yearly energy generation for different PV systems on the building - London

PV location

PV yield PV Area Area % (m2) (m2) area (kWh/ m2y)

Roof SW Façade cladding SE External shading SW External shading

1065 1130 264 264

408 306 110 204

38% 27% 42% 77%

Total PV energy (kWh/y)

Total PV energy (kWh/ m2,NFA/y)

148.2 96.1 94.1 72.2

60525 29400 10391 15638

6.44 3.13 1.12 1.66

TOTAL

115954

12.35

Orientation Tilt PV Area PV yield (kWh/m2/y) Yearly Generation (kWh/y)

S 90° 110 94.1 10391

PV on SW ext. shading Orientation Tilt PV Area PV yield (kWh/m2/y) Yearly Generation (kWh/y)

W 90° 204 72.2 15638

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6.5 Study of integrated modular façades Both façade systems are developed around the general principle of allowing good daylight levels while balancing heat losses in winter and solar gains in summer. For this reason, the façade system that is adopted for the nearly-zero building in Helsinki is focused on allowing good daylight while keeping heat losses low. The option studied for London aims at reducing the requirement for summer cooling.

The facade systems also integrate energy generation through photovoltaic panels, in line with the nearly-zero balance concept.

6.5.1. Study of a façade system for the nZE building in Helsinki The façade system proposed for Helsinki is based on the use of PV panels used as rain-screen cladding that is placed vertically between the windows and horizontally in front of a light-steel wall construction. The WWR ratio is 0.48 in this case.

The modular facade system using PV cells bonded to metallic panels is illustrated in Figure 57, which also shows the light steel spandrel wall system and perimeter edge beams with perforated webs. Structurally, the spandrel panels and vertical panels use perforated thin steel C sections (225mm deep ‘thermal studs’), and the maximum length of the spandrel is about 3m when supported by the vertical C sections that span 3.3m between the floors. The glazing system spans between the spandrel panels.

Louvres may be introduced into the spandrel panel which are hidden behind the PV units attached to them. This not only has a visual benefit but provides the possibility that the PV panel may pre-heat the air behind it that is drawn into the building on cool but sunny days in the spring and autumn.

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helsinki Figure 57. Façade system for the nZE building in Helsinki

GL

9

L1 3600

3 4 5 7

8

6

1

2

KEY 1. Gypsum board 12.5mm 2. Mineral wool insulation 50mm 3. Rigid insulation on thermal studs 175-225mm 4. External weathering board 10mm 5. PV modules fixed on studs - ventilation gap 25mm

6. Air ducts with fans and external insulated dampers 7. Cellular beam (IPE 300) 8. Steel chamber flooring system - 225mm+75mm concrete topping 9. Aluminium/timber windows with gas filled triple glazing - U <0.8W/m2 K

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6.5.2. Study of a façade system for the nZE building in London The façade system proposed for London is based on the use of horizontal and vertical shading combined with PV bonded to vertical shading, where the potential for energy generation is greatest. The two facade systems are illustrated in Figure 58.

The façade system adopted for London follows the architectural vogue to provide full height glazing combined with vertical opaque panels in high quality (Grade A) commercial buildings. The tapered floor beams allows the glazing to extend to the underside of the 300mm deep edge beam, which minimises the apparent depth of the structural system.

To control solar gains, a shading system is designed with vertical fins on the south east and south west facing walls for the reference building. Vertical shading is combined with horizontal shading which provides support and it is part of the architectural solution.

Thin film (or poly-crystalline) PV is bonded to the vertical shading elements, as illustrated in Figure 58. External louvres are hidden behind the shading system and allow air to be drawn in to the chamber floor system via a peripheral manifold next to the edge beam in order to provide night-time cooling. The edge beam is perforated by 180mm diameter circular openings at 225mm longitudinal spacing that align with each chamber. The manifold houses a small fan to draw air into the chambers and filters to control external pollution. One fan is required between the peripheral columns at 7.5 to 8.1m spacing . The manifold can be accessed from the floor above to allow for maintenance.

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helsinki Figure 58. Façade system for the nZE building in London

GL

GL

2 1

L1

FF 1 3750 L1 3600

3600

9 3 8 6 7

10 5 4

KEY 1. Unitised curtain walling system: 2. Triple glazing U<1 W/m2 K 3. Spandrel panel 4. Weathering louvres infill panel 5. Air ducts with fans and external insulated dampers 6. Cellular beam (IPE 300)

7. Steel chamber flooring system - 225mm+75mm concrete topping 8. Raised floor system 150mm 9. External fixed shading with metallic finish 10. PV modules bonded into metallic shading fin

londo

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7 FINAL OPTIMUM SOLUTIONS

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7.1 Main design features for the nearly Zero Energy case The upgrade of the reference building to the nearly Zero levels was made possible through the implementation of energy efficiency measures, starting with the building fabric, then addressing space conditioning, ventilation and lighting strategies, and ultimately by means of renewable energy generation and storage, as shown below.

Measure

Helsinki

London

Bucharest

21°C 25°C 60% (to EN 12464-1)

21°C 23°C 60% (to EN 12464-1)

21°C 25 °C 60% (to EN 12464-1)

< 0.12 W/m2 K < 0.09 W/m2 K < 0.10 W/m2 K < 0.8 W/m2 K < 0.24 > 0.45 < 0.6 m3/h·m2 Minimised Yes No

< 0.15 W/m2 K < 0.10 W/m2 K < 0.15 W/m2 K < 1 W/m2 K < 0.35 > 0.62 < 2 m3/h·m2 Minimised Not required Yes

< 0.15 W/m2 K < 0.15 W/m2 K < 0.25 W/m2 K < 1 W/m2 K < 0.35 > 0.62 < 2 m3/h·m2 Minimised Not required Yes

to Building Regs 85%

10 l/s/person (CIBSE) 85%

to Building Regs 80%

Yes

Yes

Yes

Radiant (low-temp.)

Yes Yes Yes Yes (8.4 W/m2) Yes 1,2 kW/m3s Presence + Daylight >100 lm/W < 9 W/m2

Radiant (low-temp.)

Yes Yes Yes Yes (8.4 W/m2) Yes 1,2 kW/m3s Presence + Daylight >100 lm/W < 9 W/m2

Radiant (low-temp.)

Yes Yes Yes Yes (8.4 W/m2) Yes 1,2 kW/m3s Presence + Daylight >100 lm/W < 9 W/m2

Yes Yes Yes

Yes Yes Yes

Yes Yes Yes

Yes Yes Possible No (grid-connected)

Yes Yes Possible No (grid-connected)

Yes Yes Possible No (grid-connected)

Indoor comfort standards Heating Setpoint Temperature Cooling Setpoint Temperature Max Indoor Relative Humidity Lighting levels

Building fabric Wall: U-value Roof: U-value Floor: U-value Window: U-value Glazing: g value(-) Glazing: Visible Light Transmission Air tightness @50 Pa Thermal bridges Integrated window blinds External solar shading

HVAC + Lighting System Ventilation minimum Air Flow Ventilation Heat Recovery Demand-controlled Variable Air Volume (VAV) ventilation Space heating and cooling Night cooling HVAC unoccupied setback / night setback Room-level comfort control (user-adaptive) High efficiency appliances Efficient HVAC pumps Ventilation Specific Fan Power (SFP) Sensors for lighting control Luminous efficacy of a light source Typical lighting installed power

Energy Generation Heat pump / chiller connected to the energy piles Photovoltaic Solar Thermal

Energy Storage Heating distribution buffer tank Cooling distribution buffer tank Solar heating seasonal storage (water tank) PV-electricity

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7.2 Hierarchy of measures for the nearly Zero Energy case The measures / design features that have been developed in order to reach nearly-zero energy levels reflect the hierarchical approach that is illustrated in Table 3 on page 12.

The ‘hierarchy triangle’ can be populated by the passive measures, starting with fabric efficiency and following with solar shading (for London and Helsinki). The use of thermal mass is both a passive measure, when Phase Change Material (PCM) installed at ceiling level to store heat from the room below, and active for the alternative option where the PCM layer ‘embeds’ pipework as it becomes effectively part of the heating and cooling system. The use of highly efficient building services, including daylight dimming and presence control for the lighting system, contributes towards optimising the energy efficiency of the whole building system.

The next step towards the nearly-zero energy targets is the on-site energy generation from renewable sources.

The current research has studied that aspect in detail, providing valid strategies for the design of energy piles, as well as exploring the potential for the integration of solar thermal and, most importanly, photovoltaic panels.

Guidance is provided on the preliminary sizing and design of a Building Integrated Photo-Voltaic (BIPV) system for the building used as a reference.

ALLOWABLE SOLUTIONS (outside the scope) Ground Source

ENERGY GENERATION

ENERGY PILES Heat Pumps

SOLAR THERMAL Solar collectors PV on roof & PHOTOVOLTAIC BIPV (facades + shading) pump efficiency BUILDING SERVICES Heat Heat recovery

ENERGY EFFICIENCY

LIGHTING, High-efficiency lighting, EQUIPMENT daylight dimming AND CONTROLS presence controls

ACTIVE MEASURES

PCM+heating/cooling coils

THERMAL MASS PCM at ceiling level

PCM within steel chambers

Integral shading

SOLAR SHADING External Shading

(horizontal and vertical geometries)

PASSIVE MEASURES

Window-to-Wall Ratio

BUILDING FABRIC Wall Insulation

Optimal glazing properties (Uvalue, gvalue, VLT)

Figure 59. The ‘hierarchy triangle’ adopted for ZEMUSIC to meet nearly-zero energy levels for the reference building

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Final optimum solutions

7.3 Simulations with optimum solutions: total energy demand and consumption As a result of the implementation of the measures illustrated in the previous page, a substantial reduction in energy demands was achieved for the three locations. Table 17 and Figure 59 show a comparison between the final demands for the base case and the nearly-zero energy case: these include space conditioning (heating and cooling), fans, lighting and equipment electricity. It can be noted that the greatest reductions were achieved in the heating demand, with saving ranging from 81 to 88%. The impact of energy efficiency measures, however, is generally significant, allowing a decrease in the energy demands for each category considered.

The positive benefits of implementing the sets of measures previously described can be appreciated from a final energy consumption perspective, for all locations that have been considered. The combination of an effective strategy to reduce heating loads in winter and cooling loads in summer, with the highly efficient comprising energy piles plus Ground Source Heat Pumps (GSHP), permits a remarkable reduction in the energy consumption for space heating + hot water (DHW) and for cooling. This is true for all climate zones considered, although some differences exist in the electricity use for chillers, with Bucharest needing more than three times more electricity than Helsinki (Table 18).

However, achieving a net zero balance is outside the scope of this project, as the main focus was to identify and develop nearly-zero energy solutions within the cost-optimality framework. A final balance between delivered and generated energy on-site is represented in Figure 62, in order to show how the chosen reference building can be upgraded to nearly-zero balance.

Table 17. Energy demands for base case and nZE, for Helsinki, London and Bucharest

Helsinki

London

Bucharest

Energy demand (kWh/m2 y)

Base Case

nZE Case

%

Base Case

nZE Case

%

Space heating Domestic hot water Cooling Ventilation fans electricity Lighting Equipment

80.3 8.3 9.0 15.8 22.3 25.7

15.1 8.3 13.0 11.0 9.4 18.0

-81% +44% -30% -58% -30%

71.8 8.3 14.5 15.8 22.3 25.7

14.0 8.3 7.5 11.0 8.1 18.0

Total energy demand

153.1

74.7

-51%

160.7

66.8

120

Base Case

nZE Case

%

-81% -48% -30% -64% -30%

112.4 8.3 56.8 16.4 23.1 25.7

13.8 8.3 23.8 11.1 7.5 18.0

-88% -58% -32% -68% -30%

-58%

242.6

82.4

-66%

Helsinki- BC Helsinki- nZE

100

London - BC London - nZE

80

Bucharest- BC Bucharest - nZE

60 40 20 0

HEATING

DHW

COOLING

FANS

LIGHTING

EQUIPMENT

Figure 60. Chart showing the breakdown of energy demand for BC and nZE buildings, for all locations

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Table 18. Electricity use for the Optimum nZEB Solutions for Helsinki, London and Bucharest

HELSINKI

LONDON

Electricity Use

kWh/m y 2

Electricity Use

BUCHAREST kWh/m y 2

Electricity Use

kWh/m2 y

GSHP Heating + DHW Auxiliary Heating + DHW Ventilation Cooling (chillers) GSHP Cooling Circulation Pumps Ventilation Lighting Equipment

6.2 1.9 1.5 0.1 1.1 11.0 9.4 18.0

GSHP Heating + DHW Auxiliary Heating + DHW Ventilation Cooling (chillers) GSHP Cooling Circulation Pumps Ventilation Lighting Equipment

5.8 1.5 2.0 0.2 0.9 11.0 8.1 18.0

GSHP Heating + DHW Auxiliary Heating + DHW Ventilation Cooling (chillers) GSHP Cooling Circulation Pumps Ventilation Lighting Equipment

5.2 1.1 4.9 1.1 1.0 11.1 7.5 18.0

TOTAL ELECTRICITY

49.2

TOTAL ELECTRICITY

47.3

TOTAL ELECTRICITY

49.9

energy supply [kWh]

12.6%

11.8%

3.9% AUX

GSHP

EQUIP.

4.1% 0.4% 1.8%

36.6% EQUIP.

net zero balance line

22.4%

36.6% EQUIP.

16.5%

Net ZEB

LIGHT.

LIGHT.

energy supply

10.0%

CHILLERS

2.2% 2.0%

22.6%

VENT.

19.1%

AUX

GSHP

22.4%

VENT.

2.2%

10.6%

AUX

GSHP

3% 0.2% 2.2%

36.6%

3.0%

VENT.

15.2% LIGHT.

reference building

CIRCULATION PUMPS VENTILATION COOLING (CHILLERS)energy demand [kWh] VENTILATION GSHP (COOLING)

GSHP (HEATING + DHW) AUXILIARY (HEATING + DHW)

LIGHTING EQUIPMENT

20

line

HELSINKI LONDON

alanc e

15

ero b

BUCHAREST

10

net z

ENERGY GENERATION (kWh/m2 y)

energy breakdown efficiency for the nearly-zero energy case, for Helsinki, London and Bucharest Figure 61. Pie charts showing the energy

5 0 0

10

20

30

40

50

60

70

80

90 100 110 120 130 140 150 160 170 180 190 200 210 220

FINAL ENERGY DEMAND (kWh/m2 y) Figure 62. Final energy demand and generation for base case and nearly zero energy case for Helsinki, London, Bucharest.

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7.4 Life Cycle Cost analysis Broadly, life cycle costs (LCC) are those associated directly with constructing and operating the building; while whole life costs include other costs such as land, income from the building and support costs associated with the activity within the building, as described below:

Figure 63. Diagram showing aspects considered in a Life Cycle Costing, as opposed to a Whole Life Costing analysis

7.4.1. Net Present Value (NPV) The energy savings per year (CE) from the various measures introduced in the nZE building are aggregated over ‘ n’ years based on Net Present Value (NPV) principles using the following formulae:

Where iE = inflation factor in energy cost (normally taken as 3.5% or 4%)

r = discount rate (normally taken as 7%, but can be as high as 12%)

CE = annual energy cost (or saving)

n = number of years.

For the overall economic assessment over n years, it is important that the revenue from the building exceeds the construction and other capital costs plus the operational energy and maintenance costs, as follows: NPVI > NPVE + NPVO + C where NPVI = NPV of Income (rental income for office buildings); NPVO = NPV of Operational and Maintenance Costs; NPVE = NPV of Energy Costs;

C = construction and other capital costs.

When comparing the ‘Base Case’ with the ‘Zero Energy’ Case, the differences in costs, savings and income, denoted by Δ, are considered rather than their absolute values: ΔC < ΔNPVE - ΔNPVO - ΔNPVI

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7.4.2. Capital cost of developed technologies through the use of simplified models The Base Case (BC) and nearly Zero Energy (nZE) office building designs of the office buildings are described in detail within Report 6.1 and 6.2. Capital Costs (CapEx) of different parts of the building where assumed in order to carry out a comparative LCC analysis. The simplified models of the reference building used to perform energy simulations and LCC estimates are shown in Figure 64 and Figure 65.

Simplified model parameters: Helsinki

BUILDING PARAMETERS Gross floor area, GFA: Net floor area, NFA: Total façade area, E: Façade to floor ratio, E/F:

9800 m2 9400 m2 4960 m2 0.53

Typical floor area (L0-5): Top floor area (L6): Glazed area, G: Average WWR, (G/E) WWR (open plan area) WWR (gable elevations)

1630 m2 1250 m2 1815 m2 36.6% 47.2% 2.3%

Figure 64. Axonometric view of the simplified model for Helsinki

Simplified model parameters: London BUILDING PARAMETERS Gross floor area, GFA: Net floor area, NFA: Total façade area, E: Façade to floor ratio, E/F:

9800 m2 9400 m2 4960 m2 0.53

Typical floor area (L0-5): Top floor area (L6): Glazed area, G: Average WWR, (G/E) WWR (open plan area) WWR (gable elevations)

1630 m2 1250 m2 1815 m2 36.6% 47.2% 2.3%

Figure 65. Axonometric view of the simplified model for London

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7.4.3. Difference in capital costs The same building form was used for both the base-line and nearly zero energy designs in Helsinki and London, however the facade design was different to reflect different architectural trends.

A standard solution with wall and ‘strip’ windows was costed for Helsinki. In London, however, curtain walling systems are considered to be the standard for contemporary design, particularly for city centre office buildings.

The design of PV systems was also different for the two locations, consistently with what is shown in the previous section. In Helsinki, the PV cells were integrated into the facade system on the south-east and southwest facing spandrel panels and the flank walls. In London, PV is placed on the flank walls which do not have windows, and additional PV cells are bonded to the vertically-orientated shading system on both the south-east and south-west façades. The costs resulting from the two design approaches are listed in Table 19 below.

Table 19. Summary of uplift in capital construction costs (CapEx) between Base Case and nearly Zero Energy, including cost of PV installation for Helsinki and London

Base Case

nZero Energy

STRUCTURE AND FLOORS Steel frame Hollow core slabs + topping concrete

HELSINKI

LONDON

+52.0

+52.0

-13.0

-13.0

Steel frame Steel chamber floor Concreting and reinforcement

FOUNDATIONS, PILES Piling + ground slab + pile caps Ground floor slab + pile caps

ΔCapEx (€/m2)

Energy piles Ground floor slab + pile caps

BUILDING ENVELOPE Roof + façade (inc. windows) Roof + curtain walling façade

Roof + façade (inc. windows) Roof + curtain walling façade + solar shading

MEP SERVICES (Extra costs) Radiant ceiling panels Ventilation system Pipework Chiller unit (refrigeration) Ventilation heat recovery Additional site installation costs Sprinkler system

TOTAL ΔCAPEX (€/m2)

+19.3 +65.3 +54.3

+53.2

MEP SERVICES (Integration)

-52,0

-52,0

nZero Energy + PV (roof) + PV (roof) + BIPV (façade) + PV (roof) + BIPV (façade & shading)

+60.6 +7.8 +25.5

+105.5 +7.8 +12.7 +25.5

Additional costs, as below: Ventilation system (VAV) Energy pile pipework Chiller unit (reduced in size) Ventilation heat recovery (addition) Heat pump etc.

Water tanks Solar thermal system Daylight control on lighting Electricity/district heat connection

Cash Flow €/m2,NFA

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-250

7.4.4. -300 Life Cycle Costs over 25 years -350 Helsinki

A LCC -400 assessment for Helsinki shown in Figure 66 presents the NPV of the energy generation through the PV installations on the roof and facade in comparison to the energy costs for the nearly Zero Energy Case (nZE) -450 without PV installations. The plotted values express the NPV as a difference from the Base Case (BC), that is ΔNPV = NPVnZE - NPVBC . The payback period is 8.5 years, based purely on energy cost savings.

-500

London

(1) HEL_BC _0

(2) HEL_nZE _0

(3) HEL_nZE_PVr _0

(4) HEL_nZE_PVr+fa

Cash Flow €/m2,NFA Energy Saving €/m2,NFA

The LCC assessment for London, shown in Figure 67 presents the NPV of the energy generation through the PV Year installations0 on1 the roof, on the facade (limited to the flank walls) and on the external shading in comparison 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 0 energy costs of the nearly Zero Energy case (nZE) without PV installations. The plotted values express the NPV as a difference from the Base Case (BC), i.e. ΔNPV = NPVnZE - NPVBC . The payback period is 10.5 years, based -50 purely on energy cost savings, which is slightly higher than for Helsinki because of the higher capital cost of the facade,-100 including the external shading and its PV-integrated system.

-150 -200 250

nZE CASE nZE CASE with PV on roof + facade

-250 200

-300 150 -350 100 -400

50 -450 -5000

0 1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Year

-50 -100

Figure 66. LCC chart for Helsinki, showing the cost savings over 25 years for nZE case (with and without PV) relative to Base Case.

This includes capital costs, shown as negative, and energy savings shown as positive.

Energy Saving €/m2,NFA

250

nZE CASE nZE CASE, with PV on roof + facade + external shading

200 150 100 50 0 -50

0 1

2

3

4

5

6

7

8

9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

Year

-100

Figure 67. LCC chart for London, showing the cost savings over 25 years for nZE case (with and without PV) relative to Base Case.

This includes capital costs, shown as negative, and energy savings shown as positive.

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REFERENCES 1. European Union (EU). Directive 2010/31/EU of the European Parliament and of the Council of 19 May 2010 on the energy performance of buildings (recast). s.l. : Official Journal of the European Union.

2. Torcellini P., Pless S., Deru M., Crawley D. Zero energy buildings: a critical look at the definition. s.l. : National Renewable Energy Laboratory and Department of Energy, US, 2006.

3. Sartori I., Napolitano A., Voss, K. 2012, Net zero energy buildings: A consistent definition framework. Energy and Buildings, Vol. 48, pp. 220-232. ISSN-03787788.

4. Voss K., Musall E. Net Zero Energy Buildings – International Projects on Carbon Neutrality in Buildings. Munich : DETAIL, 2011. ISBN-978-3-0346-0780-3.

5. Peel, M. C., Finlayson, B. L., and McMahon, T. A.: Updated world map of the Köppen-Geiger climate classification, Hydrol. Earth Syst. Sci., 11, 1633-1644, doi:10.5194/hess-11-1633-2007, 2007.

6.

Buso T., Corgnati S., Kurnitski J., 2014. NZEB definitions in Europe. REHVA Journal

7. Kurnitski J. 2014, FInZEB – nZEB targets and methodology development in Finland. Tallinn University of Technology, Aalto University 8. Max Fordham, 2010. Decoding Sustainability - Green Offices Sustainability Matrix. Architects Journal. September 2010.

9. Zero Carbon Hub, 2014. Zero Carbon Homes and nearly Zero Energy Buildings - UK Building Regulations and EU Directives.

10. Garde, F., Lenoir, A., Scognamiglio, A., Aelenei, D., Waldren, D., Rostvik, H.N., Ayoub, J., Aelenei, L., Donn, M., Tardif, M., Cory, S., 2014. Design of Net Zero Energy Buildings: Feedback from International Projects. Energy Procedia, International Conference on Applied Energy, ICAE2014 61, 995– 998. doi:10.1016/j.egypro.2014.11.1011 11. Voss, K., Musall, E., 2011. Net zero energy buildings: international projects of carbon neutrality in buildings. EnOB, Munich.

12. P Depecker, C Menezo, J Virgone, S Lepers, Design of buildings shape and energetic consumption, Building and Environment, Volume 36, Issue 5, June 2001, Pages 627-635, ISSN 0360-1323, http://dx.doi.org/10.1016/S0360-1323(00)00044-5.

13. Warren, E., 2008. Principles of Low Carbon Design and Refurbishment. Royal Institute of British Architects.

14. Aksamija, A., 2013. Sustainable façades: design methods for high-performance building envelopes. John Wiley & Sons, Inc, Hoboken, New Jersey.

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LIST OF TABLES Table 1. Overview of the nZEB definitions, in quantitative terms, currently available in Europe [6] Table 2. Current and proposed E-values for nZEB in Finland [7] Table 3. Max Fordham Green Office Sustainability Matrix [8] Table 4. Environmental considerations related to building depth (adapted from [13] ) Table 5. Advantages and disadvantages of long span system Table 6. Advantages and disadvantages of long span system Table 7. Main physical parameters for glazing elements Table 8. Facade design strategies for different climate zones.

Table 9. List of main physical properties for selected commercial triple-glazing systems nZEB building applications Table 10. Recommended design values for the reference building, ΔT=11 °C Table 11. Power values per building footing size, ql=39 W/m, ΔT=11 °C* Table 12. Efficiency map for PV potential: specific annual yield (kWh/kWp) for different orientations and tilt, Helsinki Table 13. Efficiency map for PV potential: specific annual yield (kWh/kWp) for different orientations and tilt, London Table 14. Efficiency map for PV potential: specific annual yield (kWh/kWp) for different orientations and tilt, Bucharest Table 15. Areas, PV yield per unit of surface area and yearly energy generation for different PV systems on the building - Helsinki Table 16. Areas, PV yield per unit of surface area and yearly energy generation for different PV systems on the building - London Table 17. Energy demands for base case and nZE, for Helsinki, London and Bucharest Table 18. Electricity use for the Optimum nZEB Solutions for Helsinki, London and Bucharest Table 19. Summary of uplift in capital construction costs (CapEx) between Base Case and nearly Zero Energy, including cost of PV installation for Helsinki and London

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LIST OF FIGURES Figure 1. Balance methodology between energy demand and supply for a reference building, compared to a NetZEB Figure 2. ECOFYS climate zones set for comparison of building performance [6] Figure 3. Hierarchical approach for Zero Carbon Buildings in the UK [9] Figure 4. Map of the Net ZEB projects worldwide Figure 5. Analysis of solution sets by type of climate, employed on a benchmark set of NZEBs (IEA Task 40) [10] Figure 6. Bird-eye view of the reference building Figure 7. Solar radiation and shadowing masks for the reference building Figure 8. Intensity of solar radiation on vertical façades, Helsinki Figure 9. Intensity of solar radiation on vertical façades, London Figure 10. Intensity of solar radiation on vertical façades, Bucharest Figure 11. Two office building by Bennetts Associates Architects. New Street Square in central London (left) and Hampshire County Council HQ in Winchester, (right) Figure 12. Type of atria Figure 13. Benefits of atria for heating, cooling and daylighting purposes Figure 15. Alternative building forms for the reference building Figure 16. Sketch showing the original building and the alternative version with a courtyard atrium Figure 14. Chart showing annual solar gains and heat losses Figure 17. Top view of the reference building, with indication of narrow plan and deep plan wings Figure 18. Three-dimensional view of the long span steel frame for one structural bay Figure 19. Modular service routing to be integrated with the floor slab Figure 21. Diagram of office section/use for the long span option Figure 20. Energy use (heating, cooling, fans and lighting) for floor depth of 12m and 17m, Helsinki Figure 22. Prefabricated composite floor system Figure 23. Modular service routing to be integrated with the floor slab Figure 24. Steel floor system with MEP routing and pipes for radiant heating and cooling Figure 25. Working principle of case 1: radiant ceilings for heating and cooling Figure 26. Temperatures and cooling power (W/m²) of radiant ceiling for warmest summer week for the three locations Figure 27. Steel floor system with MEP routing and heating/cooling pipes embedded into a PCM layer Figure 28. Working principle of case 2: radiant ceilings for heating and cooling embedded in a PCM layer Figure 29. Temperatures and cooling power (W/m²) of radiant ceiling for warmest summer week for Helsinki and London Figure 31. Steel floor system with MEP routing and air ducts for supply/extract + PCM mounted on the underside of the floor slab Figure 30. Working principle of case 3: PCM layer inside the steel chambers, without radiant ceilings Figure 32. Temperatures and cooling power (W/m²) of PCM ceiling for warmest summer week for Helsinki and London Figure 34. Steel floor system with MEP routing and air ducts for supply and extract, with PCM located into the steel chambers Figure 33. Working principle of case 3: PCM layer inside the steel chambers, without radiant ceilings

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Figure 35. Working principle of case 3: PCM layer inside the steel chambers, without radiant ceilings Figure 36. Schematic energy flows through glazing Figure 37. Radial chart showing glazing systems from the table above, according to Ug, g and Tv values Figure 39. Variation in the test room’s energy demands (heating, cooling and lighting) for different orientations, London Figure 38. Test room used for assessing the effect of orientation on energy demands Figure 40. Schematic representation of alternative options for reducing the WWR Figure 41. Solar gains and heat losses for different WWR, for south-east (solid lines) and south (dashed) orientations, London Figure 42. Solar gains and heat losses for different WWR, for south-east (solid lines) and south (dashed) orientations, Helsinki Figure 43. External shading alternatives Figure 44. Annual energy demands (kWh/m2/year) for rooms with horizontal shading for south-east orientation Figure 45. Annual energy demands (kWh/m2/year) for rooms with vertical shading for south-east orientation Figure 46. System diagram for the base line design Figure 47. System diagram for the nearly-zero energy case Figure 49. Concept diagram of integration of energy pile with heating/cooling system (left) and concept scheme of an energy pile (right).

Figure 48. Manifold collection of pipes from the energy piles Figure 50. Extracted heat for different configuration of pipes and piles for heating and cooling. Length of the single pile 20m Figure 51. Effect of building above the energy pile field instead of ambient air Results as a function of the number of energy piles and running time – only heating, pile distance 6m Figure 52. Single (left) and double (right) compartment water tanks for DHW and space heating Figure 53. Solar thermal system with DHW from Ruukki Figure 54. Photovoltaic solar electricity potential in European countries

PVGIS © EU2008

Figure 55. Location of PV panels on different parts of the reference building Figure 56. Location of PV panels on different parts of the reference building Figure 57. Façade system for the nZE building in Helsinki Figure 58. Façade system for the nZE building in London Figure 59. The ‘hierarchy triangle’ adopted for ZEMUSIC to meet nearly-zero energy levels for the reference building Figure 60. Chart showing the breakdown of energy demand for BC and nZE buildings, for all locations Figure 61. Pie charts showing the energy breakdown for the nearly-zero energy case, for Helsinki, London and Bucharest Figure 62. Final energy demand and generation for base case and nearly zero energy case for Helsinki, London, Bucharest.

Figure 63. Diagram showing aspects considered in a Life Cycle Costing, as opposed to a Whole Life Costing analysis Figure 64. Axonometric view of the simplified model for Helsinki Figure 65. Axonometric view of the simplified model for London Figure 66. LCC chart for Helsinki, showing the cost savings over 25 years for nZE case (with and without PV) relative to Base Case.

Figure 67. LCC chart for London, showing the cost savings over 25 years for nZE case (with and without PV) relative to Base Case.