Project: Design of a Zero Energy (Near Zero Carbon House) CHRISTINA ANTONELLI (Reg. NO. 120185540) ARC 6780_BUILDING ENVIRONMENTAL SIMULATION & ANALYSIS | MSC IN SUSTAINABLE ARCHITECTURAL STUDIES |
UNIVERSITY OF SHEFFIELD | 14.03.2013
Introduction This project focus on a real programme (TAO – N House) in which the developer intends to produce these type of houses on several sites across the UK. It is their intention to make these houses zero energy and near zero carbon emitters. To do this, it will be necessary to reduce the design heat losses to a minimum but also to maintain a good and healthy environment. In overall, they aim at developing a house the reach the highest levels of the Code for Sustainable Homes (CfSH) standards for environmental sustainability. Therefore, a careful analysis of the site and the climatic conditions should be carried out in order to be able to understand how the basic plan of the house should be adapted in every location and which are the best strategies to be followed. For the scope of this project it was first selected the use of Ecotect as a simulation package. There are a number of existing softwares that can be used for environmental analysis and simulation (Ecotect, Design Builder,Ecodesigner etc), each one having specific advantages and drawbacks/limitations. Design builder may be the most powerful in terms of the range of analyses that supports, however its complexity does not make it the most suitable software for early design decisions making. Ecotect is a simple tool that gives the user the possibility of testing how the thermal and lighting performance of a building is related to its orientation, the materials used, the heating-ventilation systems used etc. Thus, it is preferable to use Ecotect to understand in depth which parameters of the design are the most affective in the environmental performance of the building, and then continue using other softwares that enable you to explore these parameters further. Thus, after analyzing the models in Ecotect and bearing in mind all these parameters, the models redesigned in Design Builder in order to optimize them in terms of energy performance. Finally, they were generated the CFD results for both sites.
Design Process The analysis follows the steps below: 1. Site Analysis (Sheffield and Brighton) 2. Modeling of the house in Ecotect 3. Lighting, Thermal and Energy Consumption analysis of the house using the basic plan-orientation given by the developer 4. Analysis of the results 5. Modifying the model to improve its performance 6. Lighting, Thermal and Energy Consumption analysis again 7. Comparing the results before and after the modifications 8. Redesigning the model in Design Builder 9. Modifying the model to improve its performance 10. Final Lighting, Thermal and Energy Consumption analysis 11. Final comparing and conclusions 12. Generating CFD results using Design Builder 13. Proposal of renewable energy sources and strategies for meeting Zero Energy (Near Zero Carbon)
1. Site Analysis Sheffield Altitude: 11.0m , Latitude: 53.5째, Longitude: -1.0째
Summary of climatic data
Psychrometric Chart indicating the Comfort Zone
Monthly Diurnal Averages in Temperature
Total Annual Solar Radiation
Prevailing Winds: Whole Year
Prevailing Winds: Dec – Feb
Prevailing Winds: Mar - May
Prevailing Winds: Jun - Aug
Prevailing Winds: Sept - Nov
Brighton Altitude: 12.0m, Latitude: 51.1째, Longitude: 0.0째
Summary of climatic data
Psychrometric Chart indicating the comfort zone
Monthly Diurnal Averages in Temperature
Total Annual Solar Radiation
Prevailing Winds: Whole Year
Prevailing Winds: Dec – Feb
Prevailing Winds: Jun – Jul
Prevailing Winds: Mar - May
Prevailing Winds: Sep - Nov
From the diagrams above it can be demonstrated that Sheffield has a better solar radiation regarding to Brighton. Moreover, Sheffield accepts winds coming from West and Southwest directions for the whole year. In conjunction, the prevailing winds in Brighton are insignificant. Important is also the fact that in Sheffield the temperature differences between day and night are much bigger that in Brighton. Apart from that, the climate of the two cities does not show big variations, as they belong in the same climatic zone with slight differences in latitude and longitude.
2. Modelling the House in Ecotect The house consists of two floors and the part of vertical circulation. It has been modeled in three separate thermal zones in Ecotect: - House - ground floor zone - House - floor zone - Green house The ground floor includes the bedroom and a bathroom. The floor includes the living room, the kitchen and a bathroom. In the green zone there are the stairs which serve for accessing the two floors, and also for accessing the rooftop of the house. There is also another layer called rooftop, but it is not a thermal zone. It only includes some elements of the roof of the house. For the first analysis the house has been placed in the site in the proposed orientation from the developer.
PrintScreen of the Model in Ecotect
Sheffield: Annual Sun Path
Brighton: Annual Sun Path
Sheffield: Average Annual Solar radiation
Brighton: Average Annual Solar radiation
Sheffield: Annual Shadow Range
Sheffield: Annual Wind Frequency in site
Brighton: Annual Shadow Range
Brighton: Annual Wind Frequency in site
3. Lighting, Thermal and Energy Consumption analysis of the house They were carried out three different types of analysis. The first was lighting analysis. It looked at daylight factors (DF) % and daylight illuminance levels (LUX) in every zone. The second was thermal analysis. It looked at annual temperature distribution and monthly heating - cooling loads. The analysis was applied in every thermal zone separately and for the whole building as well. The reason behind this is that a better understanding of which areas are more vulnerable could not be assessed only from the general analysis. Finally, the third analysis was about energy consumption and it looked at daily energy use. (Energy shown as CO2 emissions). All of the analyses are shown as graphs. However, in some of them there were also generated reports with quantitative data. These reports are useful for thorough comparisons between the initial analysis and the analysis after the applied modifications. (see file: Complementary Analyses Data in CD-Rom) It should be mentioned here that the CfSH (Code for Sustainable Homes) covers nine categories of sustainable design:
Energy and CO2 emissions (M), Water (M), Materials (M), Surface Water Run-off (M), Waste (M), Pollution, Health and Wellbeing (M), Management, Ecology.
There are mandatory performance requirements in 6 categories (denoted by an M above). All other performance requirements are flexible. It is possible to achieve an overall level of between zero and six depending on the mandatory standards and proportion of flexible standards achieved. In order to check if the building meets the requirements for each one of the nine categories, assessments are carried out in two phases: 1. An initial assessment is carried out at the design stage. This is based on detailed documentary evidence and commitments which results in an interim certificate of compliance. 2. Final assessment and certification is carried out at the post construction stage. Based on the design stage review, this includes a confirmation of compliance, including site records and visual inspection, and results in a final certificate of compliance. The scope of this project is to show that the designer who takes into consideration, at the early design stage, as many of these nine factors, is capable of achieving low carbon designs. This project will focus on two of the nine categories (Energy and CO2 emissions) at the early design. The others are partly referred to the strategies that are proposed at the end. Therefore the Ecotect analyses are the most important at this early stage of design because they can produce results which inform us for the target areas of this project: 1. Which are the heat gains and losses of the building? 2. Which are the energy consumptions of the building?
3. Which are the overheating periods? 4. Does the building need to follow a ventilation, heating or an integrated approach? 5. Does the building complete the CfSH requirements for Daylight Factors and Daylighting Illuminance Levels? Requirements according to CIBSE Guide A: Environmental Design
Room Type Living Room Kitchen Dining Room Bedroom Bathroom
Average Daylight Factor (DF)% 1.5 2 1.5 1 -
Room Type Living Room Kitchen Dining Room Bedroom Bathroom
Maintained Illuminance Level (lux) 50-300 150-300 50-300 100 100
The materials that were used for this analysis are the following: External walls: DoubleBrickCavityRender (U-Value: 1.740W/m2.K – Thickness: 29 cm) (image 1) Interior walls: Brick TimberFrame (U-Value: 1.770W/m2.K – Thickness: 19.5 cm) (image 2) Roof: Plaster_Insulation_Suspended (U-Value: 0.500W/m2.K – Thickness: 21 cm) (image 3) Floors: ConcSlab_Timber_OnGround (U-Value: 0.860/m2.K – Thickness: 12.5 cm) (image 4) Windows: DoubleGlazed_Low E_TimberFrame (U-Value: 2.260W/m2.K – Thickness: 15 cm) (image 5) Doors: SolidCore_Pine Timber (U-Value: 2.310W/m2.K – Thickness: 4 cm) (image 6)
Image 1: DoubleBrickCavityRender
Image 2: Brick TimberFrame
Image 3: Plaster_Insulation_Suspended
Image 4: ConcSlab_Timber_OnGround
Image 5: DoubleGlazed_Low E_TimberFrame
Image 6: SolidCore_Pine Timber All the materials are taken from Ecotect’s material library and they have not been modified in this analysis. The thermal properties of each zone have been modified according to the images below. The modifications for the UK PART L – SBEM PROFILE can be shown to the chart below. However, they were not applied any further modifications to the details of each section of the modified parts. The details remained as default by the program.
Ground Floor: Thermal Properties and General Settings
Floor: Thermal Properties and General Settings
Green House: Thermal Properties and General Settings
Zone
Activity Level
SBEM CHP System
Fuel Type
SBEM Hot Water System
Ground Floor Floor
Dweling: Bedroom Dwelling: Dining Room Dweling: Circulation
Combined Heat and Power System Combined Heat and Power System Combined Heat and Power System
Natural gas
Dedicated hot water boiler Dedicated hot water boiler Dedicated hot water boiler
Green House
Natural gas Natural gas
Ventilation Method Natural Supply Natural Supply Mechanical
Before proceeding to the thermal analysis a check of the surface normals and the thermal zones has been done in order to check if exist any discrepancies that would lead to false outcomes.
It has been appeared this error, but it is because of the two voids that exist in the envelope of the building. The voids have been placed where the non-normal windows are. (See Ecotect file)
Normals check for each zone
Sheffield: Daylight Factor Percentage – Ground Floor (Average: 1.59%)
Sheffield: Daylighting Levels – Ground Floor (Average: 13.35 lux)
Sheffield: Daylight Factor Percentage – Floor (Average: 2.64%)
Sheffield: Daylighting Levels – Floor (Average: 224.18 lux)
Sheffield: Daylight Percentage Factor – “Green House” (Average: 54.92%)
Sheffield: Daylighting Levels – “Green House” (Average: 4667.94lux)
Brighton: Daylight Factor Percentage – Ground Floor (Average: 1.59%)
Brighton: Daylighting Levels – Ground Floor (Average: 140.49 lux)
Brighton: Daylight Factor Percentage – Floor (Average: 2.64%)
Brighton: Daylighting Levels – Floor (Average: 224.18 lux)
Brighton: Daylight Factor Percentage – “Green House” (Average: 55.01%)
Brighton: Daylighting Levels – “Green House” (Average: 4667.94 lux)
Sheffield: Temperature Distribution – Ground Floor
Sheffield: Temperature Distribution – Floor
Sheffield: Temperature Distribution – Green House
Brighton: Temperature Distribution – Ground Floor
Brighton: Temperature Distribution – Floor
Brighton: Temperature Distribution – Green House
From the diagrams above, it is shown that for all the different zones the requirements for thermal comfort have been achieved.
Sheffield: Monthly Heating – Cooling Loads (Whole Building)
Sheffield: Monthly Heating – Cooling Loads (Ground Floor)
Sheffield: Monthly Heating – Cooling Loads (Floor)
Sheffield: Monthly Heating – Cooling Loads (Green House)
Brighton: Monthly Heating – Cooling Loads (Whole Building)
Brighton: Monthly Heating – Cooling Loads (Ground Floor)
Brighton: Monthly Heating – Cooling Loads (Floor)
Brighton: Monthly Heating – Cooling Loads (Green House) From the diagrams above it is shown that there is no need for cooling, apart from the green zone of the house in Sheffield which will require a cooling load for the period of April – August. However, this load still remains insignificant.
Sheffield: Gains Breakdown (Whole Building)
Sheffield: Gains Breakdown (Ground Floor)
Sheffield: Gains Breakdown (Floor)
Sheffield: Gains Breakdown (Green House)
Brighton: Gains Breakdown (Whole Building)
Brighton: Gains Breakdown (Ground Floor)
Brighton: Gains Breakdown (Floor)
Brighton: Gains Breakdown (Green House) From the diagrams above it is shown that for both sites the green house receives almost the total amount of its gains directly from the sun or through conduction. This is explained by the fact that its material is glazing.
Sheffield: Daily Energy Use (energy shown in CO2 emissions)
Brighton: Daily Energy Use (energy shown in CO2 emissions) From the diagrams above it is shown that for both sites the energy consumption of the house is highest during the period of November – April. This is due to the heating demands for this period.
4. Results from first analysis The lighting analysis indicates that for both sites the Daylight Factor and the Daylighting Levels meet the standards required for all the different room types. However, it can be seen from the graphs that the daylight is not distributed smoothly in the interior of the house, fact that might affect the visual comfort of the occupants. Thus, in the next step, it is proposed a redesign of them, in order to achieve better distribution of daylight in the whole area of the floors. However, as long as the windows are the number one thread of heating loses, their design-size-materials should be carefully examined. For the part of circulation (green house) there are no specific standards in terms of Daylight Factor rates. Since this zone accommodates only the stair for the vertical circulation it has not been added any floor apart from the ground floor. The walls of this part of the building are from glass and thus it is ensured that daylight is penetrated adequately to the whole zone, as the analysis shows. Moreover, in the next phase, it will be considered a daylight strategy for the bathrooms which currently do not have any openings and therefore do not receive any daylight at all. Room Type
Average Daylight Factor (DF)%
Sheffield
Brighton
Living Room Kitchen Dining Room Bedroom Bathroom Circulation
1.5 2 1.5 1 -
2.64 2.64 2.64 1.59 55.01
2.64 2.64 2.64 1.59 55.01
Room Type
Maintained Illuminance Level (lux)
Sheffield
Brighton
224.18 224.18 224.18 135.35 4675.92
224.18 224.18 224.18 140.49 4675.92
Living Room Kitchen Dining Room Bedroom Bathroom Circulation
50-300 150-300 50-300 100 100 100
Requirement Achieved
Requirement Achieved
The thermal analysis shows that for both sites the annual internal temperature meets the requirements of comfort (18-22° C), as set. The heating – cooling loads show us that there is almost no need for cooling, because of the climate. The analysis was based on mixed heating and cooling system. Therefore, in the next step this can be changed only to heating, in order to minimize the energy consumption. Additionally, the thermal analysis informs about the periods that the buildings need heating. These are approximately from October – March for both sites. However, the heating loads for Sheffield are higher than these of Brighton. This is due to the overall solar radiation which is higher in Sheffield. For that reason, in the next step is explored a different orientation of the buildings, aiming at maximizing the heating gains from sun and minimizing in that way the additional needs for heating during October- March. Finally, the energy consumption analysis shows again that the period with the highest use of energy is from October to March. During the summer the consumption is minimized. The two sites do not appear big variations in their outcomes, which can be explained by the fact that their climatic conditions are very similar.
5. Modifying the model After considering the results from the analyses, there have been some modifications in the Ecotect models for both sites. The modifications have been the same because as explained above the sites’ conditions are almost the same. The first modification was to change the orientation of the buildings in order to maximize the solar heat gains. The new orientation stems from the optimum orientation for the sites, which can be found on the Ecotect weather tool. The second modification was to change the size and position of the windows of the SouthEastern façade. There were proposed three vertical windows that could improve the distribution of daylight inside the house and in the meantime could increase the heat gains. The third modification was to change the Heating system of the ground and first floor, from “Mixed Mode system” to “Heating only”. The Heating system of the green house was set to “Ventilation”, as the analysis indicated ventilation need for this part of the building during the summer season. Finally, the last modification was to add some insulation layers in the materials used, so as to decrease their UValue and improve the overall energy performance of the building. More specifically, it has been added Polystyrene Foam High Density Type 45 (thickness: 5cm) to the external walls and the roof, in order to minimize the heat losses of the house. Below are shown the new U-Values that have been achieved.
Roof External Walls
Before 0.500 W/m2.K 1.740 W/m2.K
After 0.130 W/m2.K 1.240 W/m2.K
6. Second Analysis
Sheffield: Optimum Orientation for Solar Gains
New orientation of the house
Brighton: Optimum Orientation for Solar Gains
New orientation of the house
Sheffield: Daylight Factor Percentage – Ground Floor (Average: 3.89%)
Sheffield: Daylighting Levels – Ground Floor (Average: 330.54 lux)
Sheffield: Daylight Factor Percentage – Floor (Average: 5.17%)
Sheffield: Daylighting Levels – Floor (Average: 439.58 lux)
Brighton: Daylight Factor Percentage – Ground Floor (Average: 3.81%)
Sheffield: Daylighting Levels – Ground Floor (Average: 323.48 lux)
Brighton: Daylight Factor Percentage – Floor (Average: 5.17%)
Brighton: Daylighting Levels – Floor (Average: 439.58 lux)
Sheffield: Temperature Distribution (Whole Building)
Brighton: Temperature Distribution (Whole Building) From the diagrams above it is shown that with the applied modifications the spaces of the house still remain in the temperature comfort zone for both sites.
Sheffield: Monthly Heating – Cooling Loads (Whole Building)
Sheffield: Monthly Heating – Cooling Loads (Ground Floor)
Sheffield: Monthly Heating – Cooling Loads (Floor)
Brighton: Monthly Heating – Cooling Loads (Whole Building)
Brighton: Monthly Heating – Cooling Loads (Ground Floor)
Brighton: Monthly Heating – Cooling Loads (Floor) From the diagrams above it is shown that the heating demands for both sites have been reduced. The buildings do not need energy for cooling the green house zone after the applied modifications.
Sheffield: Gains Breakdown (Whole Building)
Sheffield: Gains Breakdown (Ground Floor)
Sheffield: Gains Breakdown (Floor)
Sheffield: Gains Breakdown (Green House)
Brighton: Gains Breakdown (Whole Building)
Brighton: Gains Breakdown (Ground Floor)
Brighton: Gains Breakdown (Floor)
Brighton: Gains Breakdown (Green House) From the diagrams above it is shown that for both sites the green house gains have been reduced after the modifications applied.
Sheffield: Daily Energy Use (energy shown in CO2 emissions)
Brighton: Daily Energy Use (energy shown in CO2 emissions)
From the diagrams above it is shown that after the applied modifications the total energy consumption of the building has been reduced for both sites. The energy use in Brighton is less than that of Sheffield.
7. Comparing the Results Below are shown the results of the lighting analysis. It can be seen that after the applied modifications the spaces receive a higher amount of daylight than the required rates. Sometimes is useful to think out of minimum numbers and evaluate also the human factor in creating pleasant and livable environments. The psychological aspect of daylight in residencies is not to be disregarded in this case. Room Type
Average Daylight Factor (DF)%
Sheffield
Brighton
Living Room Kitchen Dining Room Bedroom Bathroom Circulation
1.5 2 1.5 1 -
5.17 5.17 5.17 3.89 -
Room Type
Maintained Illuminance Level (lux)
Sheffield
Brighton
439.58 439.58 439.58 330.54 -
439.58 439.58 439.58 323.48 -
Living Room Kitchen Dining Room Bedroom Bathroom Circulation
50-300 150-300 50-300 100 100 -
5.17 5.17 5.17 3.61 -
Requirement Achieved
Requirement Achieved
The second analysis shows that the overall energy consumption rates have been decreased. They still remain at high levels which mean that further actions should be taken at a next step. The analysis indicates that the change of orientation for the site of Sheffield had tremendous results in increasing the heating gains and thus reducing the heating demands. For the site of Brighton it did not work, because of the solar radiation factor which is much lower than that of Sheffield. The modification in materials’ properties improved the performance on both sites and this is what should be taken out of this analysis. There is a need of exploration of all the available materials in building industry that every designer should carry out for every single project. The proper selection of the materials can affect dramatically in the environmental performance of the building. For example, in the case of Sheffield maybe should be considered materials that have a high level of thermal lag. That is why in Sheffield the differences between day’s and night’s temperature are high. When the material gains solar heat during the day it can be stored in its volume and released at night when there is an increased need of heating. Green houses should also be considered in the design as a way to channel heated air into the domestic building. In the scheme of the TAO – N house there is the idea of greenhouse, but it should be incorporated better into the whole design strategy for low carbon emission success.
8. Redesigning the model in Design Builder In order to continue with a CFD analysis, the house was remodeled in Design Builder, allowing further exploration of materials and openings’ combinations. The house consists of two floors and the zone of the vertical circulation. The ground floor consists not only from the bedroom and the bathroom, as in the previous model, but also from a living room. The first floor consists of the dining area and the kitchen (as a single open plan space) and the bathroom. The orientation of the building remains the optimum (as stated on the second analysis of the Ecotect model). The first difference in relation to the previous model can be found on the openings. As it is shown below, the windows on the Eastern South façade are now smaller. Openings have been added to the Western South façade in order to provide daylight to the bathrooms and the Kitchen work bench that are located on this side of the building. The block of the vertical circulation has not been modeled as a green house (as before), so as to minimize the overheating of the glazing.
Ground Floor Plan
First Floor Plan
9. Modifying the model to improve its performance The second difference lies on the materials that have been applied at this stage of the analysis. Part L of the Building Regulations defines, amongst other things, the maximum U-values that various components of a dwelling must adhere to. These are limited to low values to prevent excessive heat loss, and thus reduce the amount of mechanical heating that must be supplied to the house. The requirements as set out in the 2010 version of the document are outlined below:
Several combinations of different materials have been tried out in an attempt to achieve the required U-Value limits for all the different element types. However, one main constraint which played a crucial role on the selection process was not to maximize the overall thickness of each element. This is due to the fact that increased thickness is translated into increased occupation of floor area, minimizing in that way the clear-usable area of the spaces. In addition, it was also taken into account the environmental impact of the materials used. For example, use of earth products, lime mortars and organic insulation: Mineral fibre/wool – fibre, textile organic bonded at 10, Brick-mud at 50° C , Lime sand render). These materials are low impact and healthy. Below are demonstrated the U – Values of all the elements of the building (required and achieved). Limiting U – Value (W/m2.K) Achieved U - Value External Wall 0.30 0.195 Partition 0.20 0.199 Internal Floor 0.25 0.178 Ground Floor 0.25 0.150 Roof 0.2 0.095 Window 2 0.652
-
External Wall (Thickness: 40cm) 120.00 mm Brick-mud, at 50° C 200.00 mm (Mineral fibre/wool – fibre, textile, organic bonded at 10) 60.00 mm Brick-mud, at 50° C 20.00 mm Plasterboard
-
Partition (Thickness: 30cm) 60.00 mm Brickwork, Outer Leaf 150.00 mm MW Glass Wool (high performance panels) 60.00 mm Brickwork, Outer Leaf 13.00 mm Gypsum Plastering
Internal Floor (Thickness: 40cm) -
30.00 Timber Flooring 70.00 Floor/Roof Screed 100.00 mm Cast Concrete(Dense) 150.00 mm MW Glass Wool (high performance panels) 20.00 mm Lime sand render -
Ground Floor (Thickness: 45cm) -
30.00 mm Timber Flooring 70.00 mm Floor/Roof Screed 100.00 mm Cast Concrete 239.30 mm Urea Formaldehyde Foam
Roof (Thickness: 45cm) -
20.00 mm Gravel (RG01) 80.00 mm Asphalt Mastic Roofing 150.00 mm MW Glass Wool (high performance panels) 50.00 Air gap 150.00 mm MW Glass Wool (high performance panels) 13.00 mm Plasterboard
Window (Thickness: 7.2 cm) -Trp LoE (e2=e5=1) Clr 3mm/13mm Arg
10. Final Lighting, Thermal and Energy Consumption Analyses Before proceeding to the analyses that were carried out it should be mentioned that the Design Builder library did not include weather data for Sheffield and Brighton. Consequently, there were selected available locations with the closest latitude-longitude in order to run the simulations properly. More specifically, for Sheffield it was selected Nottingham WX CTR (lat: 53.00°, long:-1.25°) and for Brighton it was selected London WEA CTR (lat: 51.50°, long:-0.12°). The first analysis was the lighting analysis and the results for every space of the building are shown below. Bathrooms and circulation spaces have not been analyzed as they do not exist specific requirements to meet.
Sheffield: Daylight Factor Percentage and Daylighting Level – Ground Floor - Bedroom
Sheffield: Daylight Factor Percentage and Daylighting Level – Ground Floor –Living Room
Sheffield: Daylight Factor Percentage and Daylighting Level – First Floor – Dinning-Kitchen
Sheffield: Daylight Factor Percentages and Daylighting Levels
Brighton: Daylight Factor Percentage and Daylighting Level – Ground Floor – Bedroom
Brighton: Daylight Factor Percentage and Daylighting Level – Ground Floor – Living Room
Brighton: Daylight Factor Percentage and Daylighting Level – First Floor – Dining-Kitchen
Brighton: Daylight Factor Percentages and Daylighting Levels These are the final results Room Type Living Room Kitchen Dining Room Bedroom Bathroom Circulation Room Type Living Room Kitchen Dining Room Bedroom Bathroom Circulation
Average Daylight Factor (DF)% 1.5 2 1.5 1 -
Sheffield
Brighton
1.491 2.208 2.208 1.567 -
1.540 2.247 2.247 1.636 -
Maintained Illuminance Level (lux) 50-300 150-300 50-300 100 100 -
Sheffield
Brighton
125.06-205.97 4.38-444.9 4.38-444.9 87.16-317.27 -
124.68-208.66 3.74-444.96 3.74-444.96 89.89-316.74 -
Requirement Achieved
Requirement Achieved
For the thermal and energy consumption analysis it was selected the following HVAC Template for both sites:
Sheffield: Comfort Analysis
Brighton: Comfort Analysis From the above diagrams it is shown that the Air Temperature for both sites remains within the comfort zone (18-22째C) for the whole year, apart from July and August which is slightly higher from the maximum level, but yet not unacceptable for the occupants.
Sheffield: Internal Heat Gains Analysis
Brighton: Internal Heat Gains Analysis From the above diagrams it is shown that for both sites the internal heat gains are almost the same, which is obvious because the two buildings are exactly the same with the same function and HVAC system.
Sheffield: Fabric and Ventilation Analysis
Brighton: Fabric and Ventilation Analysis From the above diagrams it is shown that for both sites the main fabric element for heat loss are the external walls.
Sheffield: Fuel Breakdown Analysis
Brighton: Fuel Breakdown Analysis From the diagrams above it is shown that the main energy requirement is for heating the house during the period November – March. This means that the heat gains for that period do not exceed the heat loads and thus indicates that the overheating periods are crucially minimized.
Sheffield: Fuel Totals Analysis
Brighton: Fuel Totals Analysis From the above diagrams it is shown that the house in Brighton requires fewer amounts of gas and electricity.
Sheffield: CO2 Production Analysis
Brighton: CO2 Production Analysis From the above diagrams it is shown that in Brighton the house produces less CO2 emissions.
11. Final comparing and conclusions Below are summarized the results from the analyses for both sites. These are useful to make comparisons and draw possible conclusions.
Sheffield
Brighton
As it can be demonstrated the same design can perform in a different way on different sites. In this case, the house in Sheffield produces more C02 emissions than in Brighton, which can be explained by the fact that in Sheffield the total Heating Zone requires much more energy. Moreover, the loses from glazing are almost the double in Sheffield, which is might related to the fact that in Sheffield the prevailing winds are high, in contrast to the nonexistent winds in Brighton. Thus, making the building more air tight makes sense for Sheffield. Finally, the fuel totals diagram gives information about the energy consumption. It is shown that the majority of the energy is associated with gas consumption, not electricity. The HVAC system that has been used is a gas-powered boiler that heats the water used for heating purposes. It is sure that using a gas boiler is more energy efficient than using a common one. However, it may be possible to provide water heating using solar thermal panels and reduce the demands for gas consumption more.
12. Generating CFD results using Design Builder Sheffield
Brighton
The EPC assessment indicates a rating of B for both sites. This indicates a relatively high level of performance, however it should be possible to improve the home’s performance towards an A rating.
14.Proposal of renewable energy sources and strategies for meeting Zero Energy (Near Zero Carbon) One part of designing a zero carbon building is to minimize the needs of energy consumption. However, when this target becomes unrealistic, the energy sources that will be used should be considered very carefully. For the case of Sheffield were the amount of prevailing winds is enough, it might be a solution to consider wind turbines to generate power for domestic use. Wind turbines vary from small domestic appliances capable of generating 5 W to large turbines with outputs of over 1.5 MW. Wind energy is particularly important when fossil fuels are not available (e.g. on islands) or when electricity supply is intermittent. It is also useful as a complement to solar energy on the assumption that windy grey days occur when the sun is not shining. PV and local windgenerated electricity provide a wider range of self-sufficiency than solar power alone. However, it is generally known that wind turbines operate better on large scale projects. Another point to consider, when dealing with domestic areas, is the noise and the glare noise that is being generated by the wind turbines. Thus, it requires careful design and planning before taking a decision to move forward to that direction. As already cited, one possible approach to the integration of renewable energy in the building for both sites, would be the Solar thermal System. However with almost the same cost it could be installed a PV system. The advantage of the PV system is that the type of power generated (electricity) is essential for most modern appliances in a domestic building (lights, computers, TVs, microwave ovens, electric cookers and refrigerators). Modern PV panels have a module efficiency of 15 per cent. That is, they convert 15 per cent of the primary energy of the sun directly into electricity. As a rough guide, 8-10 m2 of PV modules generate 1kW of electricity all the time over a year, or put another way, the annual output in the UK is 750-800kWh. On the examined building the total amount of the flat roof is roughly 35m2. This means that if PVs are installed on 30m2 of the roof, they can generate up to 2400kWh per year. This amount covers and provides also a surplus to the demands of electricity use in the building (as shown before the demand is roughly 1950kWh). Any PV-generated electricity that has not been consumed in the building can be fed into the national grid, which acts as an “energy store”. Another solution would be to use a simple ground source heat pump (GSHP).This system can possibly provide heating and cooling for a building by exploiting the energy store underground (geothermal energy). In the UK, the below-ground temperature is fairly constant at 9°C-13°C. GSHPs can extract this heat, either via horizontal or vertical “collectors” respectively exploiting near-surface warmth derived from sunlight, or deeper heat from molten rock well below ground level. Geothermal energy can be employed to offset seasonal variations by acting as a heat reservoir in the winter and a heat sink in the summer. As such, it reduces primary energy consumption for winter heating and summer cooling. Finally, it is always advisable to follow a holistic approach towards sustainability in every project. That is to say, the integration of renewable energy sources is only one part of this approach. There are a lot of aspects to consider. For instance: the water consumption plays a crucial role. In every project should be considered rainwater harvesting strategies, sustainable urban drainage systems (SUDS) and treatment of grey water for reuse on site. It is a fact that only 20-25% of the daily water consumption of a residence is actually for drinking purposes. The rest is used for flushing toilets and irrigation, which means that without treatment and reuse it is wasted a tremendous amount of drinking water. Another important aspect is the embodied energy of the building and how the design promotes the minimization of it, contributing to a better environment for the whole globe and not only on the scale of the project and its occupants.
From all of the above, it is clearly demonstrated that meeting a Zero Carbon house requires a number of several actions. Architects, Engineers and Designers should work together in order to achieve the best solution. Environmental Tools are proved to be really useful for targeting at more eco-friendly buildings. They have a number of potentials, and as designers we should take advantage of them from the early design stage to the final proposal of a Level 6 of CfSH homes.
References Edwards, B.(2010) Rough Guide to Sustainability.London, Riba Publishing. Hyde, R. – Watson, S. – Cheshire, W. – Thomson, M. (2007) The environmental Brief. Abingdon: Taylor & Francis. Guides •CIBSE SLL Daylighting and window design LG10 1999 •BRE Designing buildings for daylight •BRE Designing with innovative daylighting Standards •BS 8206-2 2008 Code of Practice for daylighting