D4FC Swim4Exeter Thermal Modelling Assessment
Gale & Snowden Architects & Engineers
Jan 2012
Gale & Snowden Architects
Swim4Exeter- Thermal
Page 2 of 19
Swim4Exeter Prepared by:
Jason Fitzsimmons
Checked by:
Thomas Gartner / David Gale
Project:
Swim4Exeter
Version:
Draft 02
Date:
Jan 2012
Job No:
B1112
Reference:
Projects\Current\B1112 CCA ECC Swimming Pool\Reports
Rev No
Comments
Date
This document has been produced by Gale & Snowden for the Swim4Exter D4FC scheme and is solely for the purpose of outlining the thermal modelling analysis for this scheme. It may not be used by any person for any other purpose other than that specified without the express written permission of Gale & Snowden Architects. Any liability arising out of use by a third party of this document for purposes not wholly connected with the above shall be the responsibility of that party who shall indemnify Gale & Snowden Architects against all claims costs damages and losses arising out of such use
Gale & Snowden Architects Ltd 18 Market Place Bideford Devon EX39 2DR T: 01237 474952 F: 01237 425449 www.ecodesign.co.uk Company No. 5632356 VAT Registration No. 655 9343 06
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Swim4Exeter- Thermal
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Executive Summary
There is now overwhelming consensus that the climate is changing. What is not yet fully understood is the scale of these changes. In changing climates, energy intensive buildings that do not have the means to adapt to future weather scenarios will become inoperable and too expensive to run and maintain. Energy consumption will increase as will operating costs. Swimming pool buildings by their very nature fall into this criteria of energy intensive buildings. They are currently high energy users and are prone to poor comfort control and overheating. Temperatures are commonly maintained at high levels and solar gain is usually managed by energy intensive mechanical means. In the future swimming pool buildings will become even more difficult to manage, maintain and control due to increased issues of overheating and severe weather scenarios acting on the buidling fabric – increased ultraviolet light damage, and increased driving rain and wind patterns. The Leisure and tourism industry is now one of the largest and fastest growing sectors in the UK and has grown by 13.6% between 2005 and 2009. Swimming is second only to walking as the nation’s most popular physical activity. Future trends predict the number of ’time-rich and cash-rich’ customers will rise, the leisure industry is predicted to grow and become even more energy intensive. The sector is one of the largest energy consumers and a typical 2 swimming pool complex can use in excess of 3000 kwh/m /yr. Most of the plant must operate continuously 24 hours a day over 365 days a year. They contain aggressive chemicals in moisture-laden atmospheres that require careful design and high quality materials, plant and equipment.. The industry faces significant challenges in the coming years. Much of the stock in the UK is ageing and needs replacing or refurbishing, while the hike in energy costs and the impending introduction of the CRC trading scheme means that energy efficiency is going to be crucial in determining the viability of many future centres. The poorest in society may find that they cannot afford to go swimming. This is unless swimming pool buildings are designed and built now at the outset to be robust and adapatable to the effects of climate change. The thermal modelling exercise detailed herein shows through simulation into 2030, 2050 and 2080 high carbon emmission weather scenarios that swimming pools buildings can become more energy efficient both in todays cimate and moving into future climate change scenarios through simple passive and fabric measures. This is provided consideration is given at early design stages to orientation, glazing ratios, optimising and harvesting solar gain, fabric insulation such as the passivhaus standard, thermal bridge free detailing and close control of indoor relative humidities. It is shown that orientations facing south with optimum glazing ratios will provide efficient means for reducing heating energy in warming climates without the need to use additional cooling. In addition triple glazing and a highly insulated Passivhaus envelope compared to current building regulations fabric targets can reduce heating loads by approximately 50%. The impact of orientation, glazing ratio and shading is also assessed in future climates as to is the load impact of comparing different relative humidities.
It should be noted that all modelling work is based on a simulation of reality with the input data and the weather files playing a large part. Any assumptions, as detailed in this report or agreed during the briefing process will also play a part. If conditions vary from those used, and in the case of weather this is inevitable, then there will be some variation from the simulated values in reality.
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Contents Executive Summary ....................................................................................................................................................... 3 Contents......................................................................................................................................................................... 4 1 Introduction ................................................................................................................................................................. 5 1.1 This Report ........................................................................................................................................................... 5 1.2 Thermal Modelling Software Tool ........................................................................................................................ 5 2 Weather ...................................................................................................................................................................... 6 2.1 Weather Files ....................................................................................................................................................... 6 3 Building Constructions ................................................................................................................................................ 7 3.1 Building Fabric ..................................................................................................................................................... 7 4 Internal Gains, Ventilation & Simulation Parameters.................................................................................................. 8 4.1 Internal Gains People (sensible & latent) ............................................................................................................. 8 4.2 Occupancy Patterns ............................................................................................................................................. 8 4.3 Swimming Pool Latent Heat Gains & Relative Humidity ...................................................................................... 8 4.4 Infiltration .............................................................................................................................................................. 8 4.5 Space Heating ...................................................................................................................................................... 8 4.6 Space Cooling ...................................................................................................................................................... 9 4.7 Ventilation............................................................................................................................................................. 9 4.7 Lighting ................................................................................................................................................................. 9 4.8 Zoning .................................................................................................................................................................. 9 4.9 Building Orientation .............................................................................................................................................. 9 5.0 Shading Strategies ............................................................................................................................................... 9 6 Simulation Results .................................................................................................................................................... 10 6.1 Base Case Results ............................................................................................................................................. 10 6.2 Base Case Analysis ........................................................................................................................................... 11 6.3 Changing the Fresh Air Volume ......................................................................................................................... 13 6.4 Air Change Rate Analysis .................................................................................................................................. 14 6.5 Including an Overhang ....................................................................................................................................... 14 6.6 Overhang Analysis ............................................................................................................................................. 15 6.7 Changing the Building Fabric ............................................................................................................................. 16 6.8 Fabric & Overhang Analysis............................................................................................................................... 16 6.9 Increasing the glazing on the south facing vertical facade ................................................................................ 17 6.9 Increasing the glazing Analysis .......................................................................................................................... 17 7.0 Assessing inefficient ventilation systems with heat recovery ............................................................................. 18 9 Conclusions .............................................................................................................................................................. 19 9.1 Conclusions ........................................................................................................................................................ 19
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1 Introduction 1.1 This Report This report includes the outputs and information obtained from Gale & Snowden’s in-house integrated architectural and building thermal modelling analysis design exercise for the Swim4Exeter project. The scheme is considering 3 sites in Exeter each with different constraints which will influence the building shape, size and orientation. This thermal modelling exercise is to assess 3 different orientations to provide useful information for to the design team when assessing the sites. It was decided for reasons of simplicity to thermally assess the wet pool areas only in IES and the main pool hall was chosen as this would be representative of the other pool halls. It was decided to thermally assess the dry areas using the Passivhaus Planning Package PHPP. The results of this exercise can be found in the Gale & Snowden report ‘Swim4Exeter 1 PHPP Pre-Assessment Report’ . Detailed herein are the construction details that were analysed, assumed internal heat gains, weather files utilised, software methodology and analysis, ventilation strategies, results and findings, and conclusions. The results of the various simulations detailed do not provide every simulation and analysis carried out as these have been too numerous to include and would render the report meaningless to most readers. The number of different building and thermal scenarios that can be simulated is infinite, as any alteration whether it be a construction detail to a lighting control strategy or to a window opening strategy will produce different results each time. Thermal simulations and results shown, therefore, are those considered appropriate in line with industry best practise guidelines and the experience of the thermal assessor. Hence, results detailed are those that have been found to impart the most meaningful data for comparison and analysis purposes.
1.2 Thermal Modelling Software Tool The thermal modelling software tool used to assess the proposed buildings internal comfort levels is as follows: Calculation engine: Apache Calculation engine (version): v6.4.08 Interface to Environment
calculation
engine:
IES
Virtual
The thermal modelling software tools utilised to assess the buildings thermal performance include: Calculation engine (version): v6.4.08 Interface to calculation engine: IES Virtual Environment Model tool: ModelIT Building Modeller Thermal tool: Apache Thermal Calculation and Simulation Solar analysis tool: Suncast Solar Shading Analysis Wind and air movement tool: Macroflo: Multizone Air Movement
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Figure 2 Dry-bulb temperatures Exeter 2030 DSY 50%
2 Weather
Weather files used were those that have been generated for the Exeter region by the Prometheus project at Exeter University. The Prometheus project using UKCP09 climate change projections has created a methodology for the creation of future weather files for a range of future time slices, emissions scenarios and probabilities. 4 www.ex.ac.uk/cee/prometheus
Temperature (째C)
2.1 Weather Files
All weather files used were based on the high carbon emissions scenarios (A1F1).
28 26 24 22 20 18 16 14 12 10 8 6 4 2 May
Jun
Jul
Aug
Sep
Oct
Date: Sat 01/May to Sat 30/Oct
Weather files scenarios are as follows: Dry-bulb temperature: (WG_2030_2950095_a1fi_50_percentile_DSY.epw)
Figure 3 Dry-bulb temperatures Exeter 2050 DSY 50%
Scenario 1: Exeter 1961-1991 DSY Scenario 2: Exeter 2030 DSY, 50% percentile (A1FI).
35
Scenario 3: Exeter 2050 DSY, 50% percentile (A1FI).
30
th
The 50 percentile was chosen by the design team as it represented the median of the distribution of possible climate change.
Temperature (째C)
Scenario 4: Exeter 2080 DSY, 50% percentile (A1FI). 25 20 15 10
Figure 1 Dry-bulb temperature Exeter 1961-1991 DSY
0 May
Jun
Jul
Aug
Sep
Oct
Date: Sat 01/May to Sat 30/Oct Dry-bulb temperature: (WG_2050_2950095_a1fi_50_percentile_DSY.epw)
Figure 4 Dry-bulb temperatures Exeter 2080 DSY 50%
Jun
Jul
Aug
Sep
Oct
Date: Sat 01/May to Sat 30/Oct Dry-bulb temperature: (Exeter1961_1991_DSY.epw)
Temperature (째C)
Temperature (째C)
5
30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 May
36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 May
Jun
Jul
Aug
Sep
Oct
Date: Sat 01/May to Sat 30/Oct Dry-bulb temperature: (WG_2080_2950095_a1fi_50_percentile_DSY.epw)
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Table 2: 2010 constructions
3 Building Constructions
Construction Element
3.1 Building Fabric The following is a summary of the U values, which have been calculated from constructional fabric details established by Gale & Snowden Architects, for the proposed building elements. Table 1: Solid Block Heavy Weight Construction Materials Construction Element
Roof
External Wall
Flooring
Glazing
Summary of Materials
Roof tiles Insulation Plasterboard Plaster skim
Render EWI (insulation) 215 mm concrete block work Plaster scratch coat Plaster skim
Floor tiles screed Insulation Concrete slab Insulation
Triple glazed unit g-value 0.55
Roof
External Wall
U-Value 2 W/m K
0.15
Internal Walls
Flooring 0.14
Glazing 0.16
0.82
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NCM
Building
Summary of Materials
Roof tiles Insulation Plasterboard Plaster skim
Brickwork Insulation Block Plaster
Regulations U-Value 2 W/m K
0.25
0.25
Solid Block Plaster scratch coat Plaster skim
Brickwork Concrete Insulation Chipboard Carpet
Double glazed unit g-value 0.64
0.25
1.80
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4 Internal Gains, Ventilation & Simulation Parameters 4.1 Internal Gains People (sensible & latent) People add both sensible and latent heat gains to any space they occupy. Swimming pool buildings have varying occupancy patterns throughout the day and evening and these patterns are difficult to predict when thermally assessing swimming pool designs as they can change on a daily basis and throughout the year. Therefore for reasons of simplicity people occupancy patterns were based on the following: 1 person per 12 m
2
This would allow for a steady load throughout the day taking account the peaks and troughs of occupancy. Sensible gains: 90 W / person Latent gains:
At 50-55% RH – 110 W/m At 60-65% RH – 85 W/m
2
2
Two different pool hall relative humidities (RH) were assessed (as above) to determine the energy dehumidification requirements between the two moving into changing future climates.
08:00 – 21:00 Sun
Pool water temperature was set to 28 C.
07:00 – 22:00 Mon to Fri
08:00 – 21:00 Mon to Fri 09:00 – 17:00 Sat 08:00 – 18:00 Sun
Main pool:
In order to assess humidity levels and dehumidification loads required throughout the year a pool water evaporation load is required to be included in the model. The paper ‘Accounting for Heat Losses 2 from Swimming Pools in Thermal Models ’ by Exeter University provides a methodology for calculating the evaporation of water from the pool and attributing a 2 latent heat gain in W/m to the pool hall. Using this methodology the following latent gains to the pool hall attributable to the pool water evaporation was included:
08:00 – 17:00 Sat
4.2 Occupancy Patterns
Leisure / learner pool:
4.3 Swimming Pool Latent Heat Gains & Relative Humidity
An optimum relative humidity is required in pool halls to ensure not too much energy is used dehumidifying the pool and also for adequate comfort levels. Setting the RH too low will increase the rate of evaporation from the pool water and create an evaporative cooling effect on individuals when they are not in the pool. Setting the RH too high can increase fabric condensation and corrosion of certain materials.
60 W / person
Main pool:
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07:00 – 22:00 Mon to Fri
0
4.4 Infiltration An infiltration rate of 0.6 ac/h at 50 Pa was applied to all areas within the building for the base case study. This is in line with Passivhaus design requirements.
08:00 – 17:00 Sat 08:00 – 21:00 Sun
4.5 Space Heating Fitness studio:
07:00 – 22:00 Mon to Fri 08:00 – 20:00 Sat 08:00 – 22:00 Sun
The main pool area was the focus of this study and the temperature during occupied hours was set at the 0 industry standard of 29 C.
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4.6 Space Cooling 0
A set point of 32 C was included to enable cooling if required.
4.7 Ventilation Industry guidelines such as the ‘Sports for England Swimming Pool Guide’ provide details for fresh air change rates for swimming pools at 8-10 fresh air changes per hour. This equates to a fresh air load of 17500 l/s. Based on the occupancy load detailed in section 4.1 the number of people using the pool is 63. At 12 l/s/person fresh air, the fresh air load required for people is 750 l/s. In typical modern swimming pool designs when using recirculatory ventilation systems, the air change rate is 4-5 air change per hour with 1030% being fresh air. This equates to approximately 0.5 fresh air change rates an hour. Further, a tour of a Passivhaus swimming pool in Bamberg, Germany found an air change rate of 1.5 air changes per hour with 30% being fresh air which equates to 0.5 fresh air change rates per hour. If the fresh air change rates is too high this will result in increased heating and ventilation energy loads. Larger fresh air changes rates would be required to deal with aggressive chemicals such as chlorine. It is proposed for this pool building to not use chemical treatment and to use an alternative such as ultra filtration with ceramic filters and UV treatment that uses negligible chlorine for cleaning the pool water, thus keeping fresh air loads to the minimum requirement. Fresh air load input into the IES model – 0.5 air changes per hour. Mechanical ventilation with heat recovery was also included in the temperature profile for in the incoming fresh with an effective heat exchanger efficiency of 80%.
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With poor internal daylight design, or poor control or poor layout, lighting systems can often remain switched on throughout the occupied period. A Good daylight design coupled with a well thought out lighting layout and zoned switching control in conjunction with daylight dimming control can help to ensure that lights remain switched off during the day. This is particularly when levels of solar gain thus daylight are high. A daily dimming profile that can be input as a lighting dimming control (this reacts to solar flux defined in the simulation weather file) was input into the simulations: 1 - 0.00002*(144 - 29*IFH/(IGH+0.1))*IFH
4.8 Zoning The different areas in the design of the building i.e. main pool, learners pool, changing rooms, gyms, offices etc all zones with different temperature requirements were zoned and physically separated by doors, walls and glazing. It was found at early design stages via interviews with swimming pool operators and visits to various pool buildings in particular a PHI certified pool building in Bamberg that pool buildings that did not thermally separate spaces with different temperature requirements had issues associated with poor control and poor energy consumption. This has been included for in the model. This is also investigated further in the ‘Swim4Exeter PHPP Pre1 Assessment Report’ .
4.9 Building Orientation Orientations assessed as follows with predominant glazing facing south with predominant glazing facing north with predominant glazing facing west
5.0 Shading Strategies Shading strategies assessed as follows
4.7 Lighting 2
A lighting load of 12 W/m complete with daylight dimming profile was included. With good daylight design there is no reason why the lights should not be switched off during the day.
base case with 0.5 m overhang on roof light glazing only 1m overhang included on top roof light glazing and predominate pool hall glazing.
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Figure 6 Cooling Load in MWhr/yr against orientation
6 Simulation Results
3.0
6.1 Base Case Results This initial assessment investigated the base case fabric design against different orientations for the range of climate files. Base Case = 65% RH, Passivhaus fabric, 0.5 m overhang to roof lights only, 0.5 fresh air change rate per hour.
MWhr/yr
2.5 2.0 1.5 1.0 0.5
The following figures show the number of MW hours per year for each orientation for cooling, heat and dehumidification.
0.0 South
Figure 5 Heating Load in MWh / yr against orientation
60.0
North
West
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
40.0
Figure 7 Dehumidification Load in MWh / yr against orientation
30.0 20.0
40.0
10.0
35.0 30.0
0.0 South
North
West
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
MWhr/yr
MWhr/yr
50.0
25.0 20.0 15.0 10.0 5.0 0.0 South
North
West
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
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Figure 8 Dehumidification Load in MWh / yr against Orientation at a RH reduction to 55%.
120.0
MWhr/yr
100.0 80.0 60.0 40.0 20.0 0.0 South
North
West
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
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Investigating further it was found that additional solar gain to the space was resulting in a slightly higher mean control temperature for some days than was found with the northerly orientation. Figure 9 shows this difference with the southerly orientation 0 controlling at approximately 30 C and the northerly 0 orientation controlling at approximately 29 C. Although controlling at a higher temperature, it was still below the cooling temperature on set point. The control dead band between heating and cooling was 0 0 set to 29 C to switch off heating and 32 C to enable cooling. This slightly higher temperature was also resulting in a slightly lower relative humidity between the 2 orientations especially at night. Figure 9 shows this, the light blue (south) RH curve dropping below the red (north) RH curve.
Figure 9 Space temperature (blue – north, green – south facing) against relative humidity (red – north, light blue – south).
6.2 Base Case Analysis The results detailed in figure 5 show that orientating the pool with glazing facing south has a significant effect on the heat load throughout the year. Facing south the heating load is 42 MWh/yr and facing north it is 56 MWh/yr. A difference of 16 MWh. Moving into future climates significant heating savings can still be found with a south facing orientation. Figure 6 shows for cooling the optimum orientation is north with zero cooling load. However, the cooling load when facing south is negligible in the current day climate and even into a 2050 scenario is minimal. At 2080 facing south presents a cooling load of 1.7 MWh but even this is relatively small compared to the heating savings obtained with this orientation. Reviewing the results shown in figure 7 the dehumidification loads for south and west are approximately 3 MWh/yr lower than for the north orientation. It was expected that there should be no difference in heat gain to the space when controlling 0 to 29 C whether it be from solar or a heating system, hence humidity control should not change either..
It can be seen also from figure 7 that dehumidification loads will increase moving into future climate change scenarios. The south facing scenario shows the dehumidification load at 15.9 MWhr/yr for the current DSY and increasing to 28.4 MWhr/yr in a 2080 scenario. The main reason for this is the increased moisture content available in warmer air temperatures when compared to the current DSY (see figure 10) thus increasing energy dehumidification loads.
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Figure 10 Moisture content of incoming fresh air (current DSY red against 2080 scenario (blue)
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user comfort and for protection of the fabric of the building. The later being achieved with thermal bridge free construction. The Passivhaus pool in BamberG, Germany had RH levels set to 65%RH and control was achieved with 1.5 air changes per hour at 30% fresh air. The results therefore show that the optimum moving forward into changing future climates is: south facing orientation 65% RH Close control of RH
Figure 8 details the results on the dehumidification load when reducing the RH in the pool hall to 55%. There is a significant increase in dehumidification energy requirements of approximately 60-65 MWh across all cases when compared to the results in figure 7 with a RH of 65%. It is important to note that the dehumidification loads presented by the IES simulations do not represent the full picture and are the total energy dehumidification loads for the pool and mechanical systems. They do not take account efficient mechanical processes or coefficients of performance (COPs) of plant. Dehumidification loads in swimming pool buildings are typically met in an energy efficient manner that is not detailed in these simulation results. For example, with the use of recirculation ventilation systems, thermal wheels and heat recovery units and the use of evaporators, moist external or recirculated pool air is dried out by the use of these efficient mechanical processes. The latent heat released during this process is then recovered and used elsewhere in the system to heat the incoming cold fresh air or the pool hot water requirements. In reality with this efficient mechanical process the dehumidification loads will be less than presented by these IES simulations. Nevertheless it is clear moving into future climates higher external fresh air temperatures will be introducing higher dehumidification loads. Allowing the RH to settle to around 65% in the pool hall can offer significant dehumidification energy savings which would result in lower air change rates, lower fan power and lower energy loads on evaporative cooling / dehumidification systems. It is important that the optimum RH is realised for both
From these results it can be concluded that selecting a site that enables a south facing orientation would be the optimum scenario for saving heating energy in the present and future climate scenarios. Throughout changing climates, this results in: Lower heat loads Lower dehumidification loads In addition to this and to reduce dehumidification loads moving into future climates, efficient and minimum fresh air ventilation design will be required. Designing to 0.5 fresh air changes per hour through limiting the use of chemical treatment and using efficient mechanical process such as thermal wheels and heat recovery will further reduce energy loads.
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6.3 Changing the Fresh Air Volume The original simulations included a fixed people load 2 at 1 person per 12 m . As 60 W / person was included for the latent load and 90 W for sensible heat gain to the space, both parameters represent an energy load on the system. In reality swimming pool buildings will have varying occupancy patterns and the latent and sensible loads will be less or more throughout the day. The following provides the results of the simulations when changing the fresh air change rates to 0.3 air changes to take into consideration a reduced people 2 load of 1 person per 20 m .
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Figure 12 Cooling Load in MWh / yr against fresh air change rate of 0.3 and 0.5 air changes per hour.
1.8 1.6 1.4 MWhr/yr
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1.2 1.0 0.8 0.6 0.4 0.2
Base Case = 65% RH, Passivhaus fabric, 0.5 m overhang to roof lights only, 0.3 fresh air change rates 2 and 1 person per 20 m .
0.0 0.3 ac/hr 0.5 ac/hr
Figure 11 Heating Load in MWh / yr against fresh air change rate of 0.3 and 0.5 air changes per hour.
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
60.0 50.0
Figure 13 Dehumidification Load in MWh / yr against fresh air change rate of 0.3 and 0.5 air changes per hour.
MWhr/yr
40.0 30.0
35.0 30.0
10.0
25.0 MWhr/yr
20.0
0.0 0.3 ac/hr 0.5 ac/hr
20.0 15.0 10.0
Current DSY
2030 - 50th
5.0
2050 - 50th
2080 - 50th
0.0 0.3 ac/hr 0.5 ac/hr
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
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6.4 Air Change Rate Analysis
6.5 Including an Overhang
It can be seen from figure 11 that despite the lower fresh air load for heating the incoming air the heating load at 0.3 air changes per hour is still higher than at 0.5 air changes per hour. This is attributable to the fact that the reduced people load which is also providing useful heat to the space has resulted in a higher heat requirement. In addition the simulation for incoming fresh air was simulated with heat recovery at 80% efficient thus reducing the fresh air load to a minimum due to the heat recovery effectiveness.
The base case design was simulated with the inclusion of a 1 m overhang to the predominant glazing on the main pool hall. The 3 different orientations were simulated with this overhang.
Figure 13 shows that the dehumidification load is higher at 0.5 air changes per hour, and again this attributable more to the people change in the IES simulation rather than the fresh air change rate. A reduced people load results in less moisture and latent energy to the space Assessing the impact on changing fresh air rates is not that simple as the fresh air change rate would only change in reality based on the number of people in the pool hall. Both go hand in hand. Varying people loads will have a great impact on heating, cooling and dehumidification than changes in fresh air rates. In addition there are other factors this type of cimulaiotn does not take account: An increase in people load will increase the pool evaporation rate due to the higher activity in the pool. This will in turn increase humidity thus dehumidicafiotn requirements. The evaporation of pool water will also result increase pool hall water heating when the pool water is replenished.
Figure 14 Heating Load in MWh / yr comparing base case with overhang
50.0 40.0 MWhr/yr
Figure 12 shows a reduced cooling load as is to be expected with less people providing useful heat to the space. It is still insignificant when comparing to the effects on heating loads.
Base Case = 65% RH, Passivhaus fabric, 1.0 m overhang to roof lights main glazing, 0.5 fresh air change rates.
30.0 20.0 10.0 0.0 with overhang
base case
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
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Figure 15 Cooling Load in MWh / yr comparing base case with overhang
6.6 Overhang Analysis The results in figure 14 show that including the overhang actually increases the heat load, more so than decreasing the cooling load (figure 15). During the current design summer year this increase in heating load is an additional 16 MWh / yr whilst the cooling load increase is negligible. Upon further investigation it was found that there was still a significant heat load during the summer months (see figures 17 and 18). The addition of the overhang whilst providing shading in the summer to reduce cooling also reduces the level of solar gain which was assisting the heating loads.
1.8 1.6 1.4 MWhr/yr
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1.2 1.0 0.8 0.6 0.4 0.2 0.0 with overhang
Figure 17 Heating Loads during summer periods (current DSY)
base case
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
Figure 16 Dehumidification Load In MWh / yr comparing base case with overhang
Red line represents with overhang, blue line represents without.
35.0 30.0
Figure 18 Heating Loads during summer periods (2080 – 50%)
MWhr/yr
25.0 20.0 15.0 10.0 5.0 0.0 with overhang
base case Red line represents with overhang, blue line represents without.
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
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Figure 19 Solar Gain – 10 day period in July with overhang and without (current DSY)
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Figure 20 Heating Load in MWh / yr - Passivhaus vs 2010 fabric
90.0 80.0
MWhr/yr
70.0 60.0 50.0 40.0 30.0 20.0 10.0 0.0 Yellow line represents with overhang, red line represents without.
passivhaus NCM 2010 Figure 16 also shows that the addition of the overhang which reduces solar gain has a knock on effect of also increasing the dehumidification load. The results show that that including an overhang has a detrimental effect on the energy requirements for the building. There is still a heating requirement during the summer months which is due to the high temperature requirement within the pool space of 0 maintaining 30 C all year round. Any solar gain that can contribute to this provided the optimum is found with cooling loads will reduce this heat requirement.
6.7 Changing the Building Fabric The overhang was left in and the thermal fabric performance was altered to those that represent 2010 Uvalues. Both were then simulated together and compared to the Passivhaus fabric. Infiltration was kept at 0.6 air changes at 50 Pa during normal operating conditions for both fabric approaches. Base Case = 65% RH, Passivhaus fabric & 2010 fabric, 1.0 m overhang to roof lights main glazing, 0.5 fresh air change rates.
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
6.8 Fabric & Overhang Analysis Figure 20 shows that reducing the building fabric thermal properties from Passivhaus to 2010 thermal targets almost doubles the heating load. During the current DSY the change is from 49 MWh / yr to 89 MWh / yr. In addition the 2010 simulation does not take account the weakness in thermal bridging and the higher infiltration rates as will be expected with this type of construction. The difference in cooling between the two is insignificant and there is a slight increase in dehumidification load. It can clearly be seen that the Passivhaus fabric approach and minimising thermal bridging is an important factor when designing for high heat loads in swimming pool buildings more so than for most other building types. It was found for both approaches including the glazing overhang that cooling was not a factor.
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6.9 Increasing the glazing on the south facing vertical facade
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Figure 23 Cooling Load in MWh / yr – Doubling the Glazing Area
It was decided to assess the impact of doubling the glazing area on the south facing vertical facade would have on the building into future climates.
7.0 6.0
Figure 21 IES suncast image showing doubling of the glazing on the south facade
MWhr/yr
5.0 4.0 3.0 2.0 1.0 0.0
Simulation 1: The base case design facing south without overhangs on the vertical glazing.
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
Simulation 2: Doubling the south facing glazing without overhangs Simulation 3: Doubling the south facing glazing and including 0.5 overhangs. Simulation 4: As 3 but using the ventilation system in summer bypass mode without heat recovery Figure 22 Heating Load in MWh / yr – Doubling the Glazing Area
45.0 40.0
MWhr/yr
35.0
6.9 Increasing the glazing Analysis It is clear that increasing the glazing without the use of an overhang will reduce the heat load further by approximately 3-4 MWhr/yr across the climate change scenarios. It will also increase the cooling load by 3 MWhr/yr in 2050 and by 5 MWhr/yr in 2080. In 2080 this negates the heating savings made. Including an overhang provides some heating savings at about 1 MWhr/yr across the climate change scenarios. Until 2050 the cooling load increase is below 1 MWhr/yr and then in 2080 the increase is an additional 1.7MWhr/yr. The cooling load is then significantly reduced by using the ventilation system in summer bypass mode and not in heat recovery.
30.0 25.0 20.0 15.0 10.0 5.0 0.0 Simulation Simulation 1 Simulation 2 3 Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
It can be seen that increasing the glazing and including an overhang could be considered if extra daylight levels or views out are required as there will be marginal decreases in energy.
7.0 Assessing inefficient systems with heat recovery
ExtraCare4Exeter - Thermal Modelling
ventilation
Finally it was decided to assess the impact of not utilising heat recovery to recover exhaust energy to pre-heat the incoming fresh air to assess the impact on heat loads into future climate change scenarios. Figure 24 Heating Load in MWh / yr – Ventilation Heat Recovery Analysis
120.0 100.0
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Figure 25 Dry-bulb temperatures Exeter 2080 DSY 50%
Temperature (°C)
Gale & Snowden Architects Ltd
36 34 32 30 28 26 24 22 20 18 16 14 12 10 8 May
Jun
Jul
Aug
Sep
Oct
MWhr/yr
Date: Sat 01/May to Sat 30/Oct
80.0
Dry-bulb temperature: (WG_2080_2950095_a1fi_50_percentile_DSY.epw)
60.0 40.0 20.0 0.0 with heat recovery
no heat recovery
Current DSY
2030 - 50th
2050 - 50th
2080 - 50th
The results are very clear, efficient mechanical ventilation process with heat recovery pre heating incoming fresh air supplies will provide significant savings in heating energy. This is because of the 0 high internal temperatures set at 30 C, fresh air loads will require heating for most of the year. Even in a 2080 scenario the external air temperature rarely 0 exceeds 30 C as can be seen in figure 25.
Gale & Snowden Architects Ltd
ExtraCare4Exeter - Thermal Modelling
9 Conclusions 9.1 Conclusions This report and thermal modelling exercise has assessed various orientations suitable for the 3 sites proposed for the swimming pool scheme in Exeter. It is clear that maximising solar gain, orientating south and adhering to a robust insulation and air tightness standard such as that of the passivhaus institute is the optimum. Super insulating, triple glazing harvesting solar gain will be especially important in warming climates and will help provide climate change adaptive means for reducing high heating energy consumption in swimming pool buildings. Solar gain is both useful during winter periods and summer periods. This is due to the high internal temperature requirement all year round. The use of efficient mechanical processes and heat recovery will become even more prevalent in future swimming pool buildings in particular at reducing dehumidification loads and heating colder incoming fresh air loads.
10 Bibliography 1. Swim4Exeter PHPP Pre-Assessment Report, T Gartner, G&S Architects 2012 2. Accounting for Heat Loss in Swimming Pools, T Kershaw, Exeter University 2012 3. Sports for England Swimming Pool Design Guide 2011 4. Eames M, Kershaw T, Coley D, BSER&T 32 127 (2011) and the web address in the reference section: www.ex.ac.uk/cee/prometheus
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