CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
JEAN MCKENDRY NEIGHBOURHOOD CENTRE – ENVIRONMENTAL AND ENERGY MODELLING REPORT TABLE OF CONTENTS PART 1. INITIAL INVESTIGATIONS 1.1 1.2 1.3 1.4 1.5
page 3
page 4
page 5
page7
page 8
page 9
Site Description Existing Building Existing Construction Existing Systems Main Flaws
PART 2. LIMITATIONS
2.1 Assumptions 2.2 Base Model 2.3 Results 2.4 Disclaimer PART 3. BUILDING FABRIC 3.1 External Walls 3.2 Internal Partitions 3.3 Ceiling 3.4 Roof 3.5 Windows 3.6 Doors PART 4. SYSTEMS
4.1 Labyrinth 4.2 Underfloor Air Distribution 4.3 HVAC Active System PART 5. THERMAL COMFORT
5.1 Temperature Band 5.2 Base Model – systems off 5.3 Base Model – systems on 5.4 Accurate Model – systems off 5.5 Accurate Model – labyrinth on 5.6 Accurate Model – all systems on 5.7 Carbon Dioxide levels PART 6. LIGHTING
6.1 Artificial Lighting 6.2 Natural Lighting
1
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
PART 7. ENERGY
7.1 Lighting 7.2 Space Conditioning 7.3 Total Energy 7.3.1 Base Model 7.3.2 Insulation 7.3.3 Labyrinth 7.3.4 HVAC 7.3.5 CO2 Bypass 7.4 Summary 7.5 Renewables
page10
page 11
page 12
PART 8. CONCLUSION AND FURTHER IMPROVEMENTS 8.1 Conclusion 8.2 Costs Analysis 8.3 Further Improvements PART 9. APPENDIX
9.1 Temperature Graphs 9.2 Energy Totals 9.3 HVAV Schematic TERMS AND UNITS The building: refers to the Jean McKendry Neighbourhood Centre Modelling: refers to environmental and energy simulations run on the building HVAC: Heating Ventilation Air Conditioning Systems: refers to conditioning equipment used for space conditioning CO2: carbon dioxide ppm: parts‐per‐million, a measure of concentration R‐value: measure of insulation, the higher the value, the better the insulation U‐value: measure of insulation, reciprocal of R‐value. The lower the value, the better the insulation. Usually used for windows SHGC: Solar Heat Gain Coefficient Tvw: Visible Light Transmittance IEQ: Internal Environment Quality l/s: litres per second, measure of rate of air flow kW: kilowatts, measure of equipment power MWh: megawatt‐hour, measure of energy used PV: photo‐voltaic This report is meant to be read in colour.
2
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
PART 1. INITIAL INVESTIGATIONS 1.1 Site Description The site is located at 91‐111 Melrose Street, North Melbourne. It covers an area of approximately 1200 m2 and is oriented 7.9° due north. The site is bordered by the street on one side (east) and a child care centre on the other (west) and the two shorter sides (north and south) are lined with adjacent buildings. Surrounding trees and two large social housing towers provide a considerable amount of shading. 1.2 Existing Building The building is described as a neighbourhood centre aimed mainly at older people for purposes of recreation and social activities. It fits a hall that can accommodate up to 100 people, a commercial kitchen, a small stage area and several smaller rooms. There is also an exterior open terrace along the western wall. 1.3 Existing Constructions External brick walls Ceiling tiles Vinyl on concrete floor Single glazed windows in timber frames Spandrel panels under windows in the hall Fully glazed entrance door/wall inside aluminium frame Unknown roof construction
1.4 Existing Systems 45kW gas‐powered split system air conditioning in the main hall Gas‐fired radiant heater inside the main hall (no longer used) Individual split system air conditioning units (estimated 5kW each) at some of the smaller rooms Evaporative cooler inside kitchen Fluorescent lighting 1.5 Main Flaws The main flaw of the building lies in the building fabric – the constructions used do not provide sufficient levels of thermal insulation, with no insulating material being installed. The windows are single glazed and allow heat transfer heat very easily. Permanently open gridded vents (initially installed as exhausts for the gas radiant heaters) also leak heat into and from the building without serving any purpose any more. The consequences are: In the summer: the heat from the outside air is easily transferred into the building by conduction through the walls, windows and roof, and by radiation through the glazed surfaces (solar heat gain). In the winter: the heat from the inside is easily lost similarly through conduction, and the warm air itself rises moves out of the building through the open vents (convection).
3
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
PART 2. LIMITATIONS 2.1 Assumptions The entire process of modelling involves a certain level of assumption in the way the building is used. The main assumption and the one having the most impact on the results is the occupancy. The level of occupancy will determine when and how much conditioning will be required and when lights and equipment will be used. All of the above will impact on the thermal performance and the overall energy use. For purposes of modelling, the assumptions made for occupancy will be during weekdays, from 8am to 6pm. These will be referred to as the Occupied Hours. 2.2 Base Model The process of modelling started with modelling the building with the existing to obtain a series of results that would be used as a benchmark. These results will be referred to as the Base Performance. All the subsequent results are compared against the base case in order to show progression. It is important to use the same assumptions when running subsequent models so that the comparison of results is significant. 2.3 Results The results that will outcome from the most optimal model will be based on the assumptions made about the occupancy of the building. In this report the results from this model will be referred to as the Accurate Performance. The results of the building as it would perform in reality after the interventions have been applied will be referred to as the Actual Performance. The most accurate these assumptions, the closer will the Accurate Performance be to the Actual Performance. A specific set of information obtained from benchmarking bodies such as GreenStar or NABERS can be fed into the model as a substitute for the assumptions. The results obtained from this model will be referred to as the Benchmark Performance. Benchmarking is used for obtaining ratings and Benchmark Performance will most of the time be different from Accurate Performance. Benchmark Performance cannot be used as a measure of how the building will perform, and Accurate Performance cannot be used for rating purposes. 2.4 Disclaimer The results obtained from the modelling (Accurate Performance) will be the direct result of the information provided by the client. The modelling process will not be responsible should major discrepancies arise between the Actual and Accurate Performances as a result of the spaces being used in a way widely different from intended. Nevertheless, regardless of how the building will be used, comparing the Accurate Performance and the Base Performance will be an indication of the improvements made to the buildings.
4
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
PART 3. BUILDING FABRIC The first intervention made onto the base model was to improve the insulation of the building fabric. The spandrel panels were removed and the vents were permanently closed. 3.1 External Walls
One feature of the building fabric that is very desirable is the thermal mass in the form of bricks. The thermal mass will help lower undesirably high temperatures, and raise undesirably low temperatures. In the new construction, the brick wall is retained and is also insulated on the OUTSIDE to prevent temperature transfers, while still leaving the thermal mass in contact with the inside air. Layers from inside to outside: brick leaf, cavity, brick leaf, polyurethane board, rendering. Total R‐value: R5.6.
3.2 Internal Partitions The internal partitions are also made brick to provide still more thermal mass. The partitions are not insulated. 3.3 Ceiling
Much of the heat is lost through the ceiling/roof spaces, this is why it was important to have proper insulation there. For the accurate model, having high insulation on the ceiling level did have a significant impact on the thermal performance of the building. Layers from inside to outside: ceiling tiles, plywood, polyurethane insulation, plywood. Total R‐value: R17. 3.4 Roof With the glazing introduced at the ceiling partition, it was important to have a properly insulated roof so that most of the heat/cold is already blocked at the roof before it gets to the ceiling partition. Layers from inside to outside: Polyurethane insulation, plywood, asphalt coating. Total R‐value: R12. To be discussed further in Part 6. Lighting (section 6.2) 3.5 Windows 3.6 Doors
To obtain a maximum insulation from the windows, triple glazed windows inside timber frames are used. Windows are low‐emissivity to avoid solar heat gain. The windows are also equipped with internal shades that automatically lower at an incident radiation of 500W/m2. Internal glazing at the ceiling and saw tooth roof use similar constructions (except for the shading device.) The window system is modelled to match the properties of the best performing Paarhammer triple‐glazed window. SHGC: 0.19, Tvw: 0.29, Air Infiltration: 0.05. WERS rated U‐value: 0.9
5
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
PART 4. SYSTEMS 4.1 Labyrinth The building is sitting on a void that serves no purpose. Using that space to fit a labyrinth can have several benefits (refer to section 5.3.) The labyrinth’s purpose is to passively condition the air using the temperature of the ground. It is made from large masses of concrete that is used to ‘store’ the temperature of the ground and transfer it to the air. Above ground, the labyrinth is insulated on the outside to prevent external air temperature from affecting the temperature of the air inside. Distribution fans are used to circulate the air through the labyrinth and into the rooms. The labyrinth has an above ground wall R‐value of R8 and a ceiling R‐value of R8 (between occupied level and labyrinth.) 4.2 Underfloor Air Distribution System The air from the labyrinth is distributed into the rooms through an underfloor distribution system. The advantage of the underfloor system is that as the air rises, it carries away all the contaminants up and is flushed out through the ceiling.
Stratospheric zone
Occupied zone
Another advantage of the underfloor distribution is that the conditioned air is delivered right where it is needed – i.e. at the occupied zone. In this way, a lesser volume of air needs to be conditioned (the volume of air at the stratospheric zone does not need to be conditioned since it is not occupied.) Both fresh air and conditioned air (which is the same most of the time) are distributed through the underfloor and up into the spaces.
Underfloor zone
4.3 HVAC Active Systems Unlike the Base Case that had different conditioning systems for every room, the Accurate Model makes use of the same HVAC system throughout the entire building. The system is used in conjunction with the labyrinth and is responsible for both conditioning and fresh air distribution. The system consists of two 5000l/s distribution fans for heating and cooling and a 3000l/s distribution fan for fresh air distribution. The cooling component is a 30kW direct expansion cooling system and the heating component is a 28kW air‐to‐air pump. A high efficiency 0.25 kW tube heat exchanger is also used to recover most of the heat leaving the building. Temperature and carbon dioxide sensors are used to control the air flow and the heating and cooling coils so that they run only when required. Heating fan and coil are triggered at 18C° and cooling fan and coil are triggered at 25°C. Carbon dioxide fan is triggered at 600ppm of CO2. The entire system is set to operate only during Occupied Hours (Refer to appendix 9.3 for HVAC schematic.)
6
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
PART 5. THERMAL COMFORT 5.1 Temperature Band The temperature range that is set in this model as the comfortable range is between 18°C and 25°C. 5.2 Base Model – systems off For the base model, the average room temperature ranges for Occupied Hours during the year, without conditioning are as follows: < 18°C 49.2%
18°C to 25°C 31.1%
> 25°C 19.7%
5.3 Base Model – systems on The HVAC system for the base model is set to run without any limit on the power requirement, and during that time the temperature is 100% of the time between 18°C and 25°C, but at the cost of higher power requirements. 0%
100%
0%
5.4 Accurate Model – systems off With the added insulation and without conditioning, the temperature ranges during the Occupied Hours during the year are as follows: 24.8%
45.4%
29.8%
5.5 Accurate Model – labyrinth on With the added insulation and with the air being drawn into the building from the labyrinth, the temperature ranges for the Occupied Hours during the year are as follows: 2.2%
87.2%
10.5%
The temperature of the air from the labyrinth is naturally conditioned by the ground and the thermal mass and is closer to the average 20°C of the ground. As reference, when the outside air temperature is at 39°C in the peak of summer, the labyrinth air temperature is at 26°C, and when the outside air temperature is at 0°C in the low of winter, the labyrinth air temperature is at 6°C. The labyrinth is therefore much more efficient at cooling, with the only power requirement being for the fans distributing the air into the spaces. 5.6 Accurate Model – all systems on With added insulation, labyrinth and active systems on, the temperature ranges for the Occupied Hours during the year are as follows (only for conditioned spaces): 0.4%
97.9%
1.6%
7
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
The above results show that the Base Performance is better than the Accurate Performance under the same conditions (active systems running during the Occupied Hours). An important energy component of the results that will justify this slight drop in performance will be discussed in Part 7. The graph above shows the temperature of a typical conditioned space of the accurate model with all space conditioning systems ON. The blue band represents the 18‐25 comfort zone. The peaks outside this band happen mostly outside the Occupied Hours. 5.7 Carbon Dioxide Levels Since the heating and cooling is distributed through air from the labyrinth, the air entering the spaces is always fresh air. Paired with dedicated distribution fans that run only to bring in fresh air, the heating/cooling system assures that carbon dioxide levels always remain to a minimum. The dedicated carbon dioxide prevention fan is activated when the interior carbon dioxide levels reach 600ppm. The blue graph shows the typical CO2 levels in the Base Model with windows closed. The red graph shows the typical CO2 levels in the Accurate Model (never exceeds 600ppm). A simulation was run on the base model with window profiles opening at 600ppm CO2 levels to try to achieve similar 600ppm levels – in terms of CO2 levels it was successful, but considerably increased the amount of energy required for conditioning (see Part 7.)
8
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
PART 6. LIGHTING 6.1 Artificial Lighting Fluorescent lights are less efficient than LEDs, which means that for the same amount of light, more energy is ‘wasted’ in the form of heat. While this might be a desirable feature in the winter, in the summer, when the space needs cooling, fluorescent lights do use more energy to achieve the same levels of lighting, while still producing heat. For the Accurate Model, LED lights were used because of their energy benefits. The energy analysis is made in Part 7. 6.2 Natural Lighting According to some research, the quality of natural light is better for the occupants because it changes throughout the day and therefore allows people to connect better with their natural environments. People also tend to perform better under natural light, and from an energy perspective, natural light is free. Currently the building has very limited access to natural light (only through the windows). The hall will be used as a case study to analyse light levels and compare the affected thermal performance. The above diagrams show the base case and the natural light infiltration. The sides having windows have fairly high lux levels, dropping very quickly towards the centre of the room – a large proportion of the room has a lux level of between 100 and 300. With the addition of the green roof over the terrace to minimise solar gain, the natural light infiltration further decreased and the overall lux levels consequently dropped as well – a large proportion of the room has a lux level of between 50 and 150.
9
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
A strategy was to introduce light through the roof using a saw tooth roof. Introducing glass into the roof and ceiling construction considerably lowered their thermal performance. For this reason, triple layers of glass are used to the outside, and between the room and the ceiling space. Windows face south to minimise solar heat gain and provide a north facing sloping surface to accommodate the solar panels. The lowest glass layer is translucent to diffuse the light into the space.
Outside space Sloping surface to accommodate PVs
Triple‐glazed south facing windows
Ceiling space
Translucent layer to diffuse light
Room space
With the sawtooth roof, a much higher level of natural light is allowed into the space. The average lux level across most of the space is between 300 and 700, levels suitable for offices and classrooms. The introduction of the glass did affect the thermal performance of the model, but the benefits outweighed the cost of additional conditioning. PART 7. ENERGY 7.1 Lighting As mentioned previously, changing the lighting from fluorescent to LED had an impact on both the direct energy consumption of the lights themselves, and also for the heating. The modelling has shown that fluorescent lights saved 0.5MWh of heating during the winter, but overall consumed 3MWh more electricity than LEDs. The LEDs were therefore a better option. The saw tooth roof introduces plenty of natural light, thus diminishing the required amount of artificial lighting. However the glazing affected the building’s fabric thermal performance, resulting in more required active conditioning. The overall additional energy required, taking into account these two factors, is 0.2MWh per year.
10
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
7.2 Space Conditioning In the modelling process, there were many factors that could affect the amount of space conditioning required. To keep track of the process more efficiently, these elements were broken into four distinct components (insulation, labyrinth, HVAC, CO2 bypass) that would be controlled separately to observe their effect onto the thermal performance. 7.3 Total Energy 7.3.1 Base Model The total energy used by the base model was 88 MWh, but with no openings, always had an excess of CO2. Having window profiles opening at a specific CO2 level resulted in acceptable levels of CO2, but required 40MWh of additional energy annually to condition the space. 7.3.2 Insulation With better insulation, the amount of conditioning required to condition the same closed space was reduced by 65MWh annually. 7.3.3 Labyrinth The labyrinth, like the insulation, acts as a passive system. The only energy required for the labyrinth is for the distribution fans (3.1 MWh/year.) 7.3.4 HVAC The combination of the labyrinth, proper insulation and efficient heat exchange means that the HVAC does not actually need to operate excessively. In the most efficient model, the HVAC (including distribution fans) uses 16MWh of energy annually to keep the building to comfortable levels. 7.3.5 CO2 Bypass Since the fresh air is brought in by the space conditioning, the CO2 bypass system only operates when the system is not active – the only energy used then is for the distribution fan (0.7MWh/year.) 7.4 Summary The table below shows the different total annual energy uses at various stages of improvement. Thermal comfort and carbon dioxide are given as a percentage of Occupied Hours within the acceptable limits. Thermal comfort: between 18°C and 25°C Carbon dioxide levels: below 600ppm Stage Base model, all systems on Base model, with CO2 window profile Accurate Model, generic 35kW HVAC Accurate Model, insulation only Inclusion of Labyrinth Inclusion of HVAC Inclusion of CO2 Bypass (all systems on) Inclusion of LED lights Inclusion of Saw Tooth Roof
Thermal comfort 100 % 100% 100 % 45.4 % 87.2 % 98.4 % 98.0 % 98.0 % 97.9 %
Carbon dioxide 0 % 92.2 % 0 % 0 % 43.1 % 43.1 % 97.8 % 97.8 % 97.8 %
Total energy 88.3 MWh 127.9 MWh 23.0 MWh 8.1 MWh 11.2 MWh 26.7 MWh 27.4 MWh 24.9 MWh 25.1 MWh
It is tempting to believe that ‘Inclusion of LED lights’ stage is a better option, but the degree of natural light allowed through the saw‐tooth roof justifies the additional 0.2 MWh of energy required and the drop of 0.1% of the occupied time outside the comfort band.
11
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
7.5 Renewables The building has been fitted with photovoltaic cells onto the roof to generate electricity onsite. Today solar panels developed by Sharp can be as efficient as 44.4% of energy conversion. More realistically, for commercial purposes, solar panels along the lines developed by SunPower X‐series can have efficiencies up to 21.5%. The solar system used for modelling purpose is as follows: Monocrystalline panels Efficiency: 20% Shading factor: 0.7 Azimuth: 0° (North facing, see diagram in section 6.2) Inclination: 30° Area covered: 125 m2 (approximately 30% of total roof area) Total energy generated: 26.0MWh per year – more than the energy used by the building. PART 8. CONCLUSION AND FURTHER IMPROVEMENTS 8.1 Conclusion The Base Model achieved slightly better thermal comfort levels, but the rest of the IEQ, in terms of air quality and lighting, was compromised. The final performance of the Accurate Model shows that the building can achieve very high levels of thermal comfort, low carbon dioxide levels and good levels of natural light infiltration during Occupancy Hours with a much lower energy requirement (71.6% reduction.) 8.2 Costs Analysis Several systems had to be set up in order for the building to perform better. Without doubt, the better performing building will cost more money to build (or cost a fair amount to retrofit the systems). This being mentioned, with the improved performance of the building, a fair amount of energy is saved every year. At current buying and selling rates of 25c/kWh and 8c/kWh respectively, the potential savings are as follows: With PVs Without PVs
Initial energy 88.3 MWh 88.3 MWh
Final energy ‐0.9 MWh 25.1 MWh
Difference 89.2 MWh 63.2 MWh
Money saved/year $ 22 147 $ 15 800
8.3 Further Improvements The model can be further improved by the implementation of better systems – better insulation, more efficient HVAC systems, more surface contact on the thermal mass inside the labyrinth. However, these additions can be very expensive, without an equally significant enhancement in one aspect of the building performance. A more thorough cost‐benefit analysis has to be made in order to better understand at what point it is no longer financially worth improving. The analysis could go further by analysing not only from a cost perspective, but from an environmental/carbon one – for example, the inclusion of more concrete could cheaply have a significant impact on the performance of the building, but heavily affect its carbon footprint (concrete has a very high carbon footprint). Similarly, more efficient PVs could be imported from Japan or Europe, but again adding to the carbon footprint in the form of travel.
12
CHU SIN CHUNG Adrian 332874 Complex Building Energy Modelling ABPL90153 Final Report Chris Jensen
PART 9. APPENDIX For reference, some additional information has been included in this appendix. 9.1 Temperature Graphs
Base model with all systems on
Accurate model with all systems
9.2 Energy Totals Month January‐February March‐April May‐June July‐August September‐October November‐December Total
Base Model 7.8 MWh 8.1 MWh 22.3 MWh 28.1 MWh 14.2 MWh 7.8 MWh 88.3 MWh
Accurate Model 2.7 MWh 3.4 MWh 5.2 MWh 5.7 MWh 4.6 MWh 3.5 MWh 25.1 MWh
9.3 HVAC Schematic
air in active system
labyrinth
rooms conditioned
air out
13