CASE STUDY | HOULTON SCHOOL Because the school will not be fully occupied for several years, there was an additional benefit to only heating the water being used. Gas is used to heat the new sports hall block and the two historic buildings. Three heating boilers and a gas-fired direct water heater that provides hot water for the sports hall showers are located in the sports hall plantroom. Locating them in one of the new blocks avoided the need for a flue on the historic blocks. The sports hall services are configured to shut off links to other buildings using valves and dampers to enable the community to use certain areas of the building out of school hours. Soffit-mounted, low temperature hot water radiant panels, based on a 70oC flow temperature, heat the sports hall and the double and triple height spaces in the historic buildings, including the assembly and dining halls. The gas-fired boilers also heat the domestic hot water, via a buffer tank, to the toilets and schools kitchen in the Power Hall building. South says the use of gas would be something wed look to change if we were designing the project now, because it would be possible to provide heat with a heat pump system. The project used a design and build contract. Following an as-built analysis, the design team concluded that in future they would provide contractors an energy consumption impact with all proposed value engineering options, and that they would monitor estimated energy consumption impact of any design changes proposed. The final (as-built) predicted energy consumption meets DfE requirements, and is in the 10th percentile for new schools, with an average heating energy demand of about 25 kWhm-2 per year for the new buildings. What this project shows is that with a creative architect and innovative approach to low energy and building services design it is possible to repurpose almost any historic structure. This is important because we need to prioritise the retrofit of existing building stock over demolition to help minimise the carbon embodied buildings and Houlton School shows that retrofit can deliver something unique and exceptional. CJ The Power Hall houses the dining and assembly hall buildings lose heat at a faster rate than they do in reality, which reduces the need for redundancy in heating plant because redundancy has effectively been built into the fabric. As a consequence, he says there is often an opportunity to reduce the amount of the heating plant to help balance the cost of fabric enhancements. On the new build school blocks, it would probably be a week before theyd notice the heat pump had failed, he laughs. On this project he says Hoare Lea did a really good job of striking the right balance. Domestic hot water (DHW) is supplied using direct electric heating at point of use in the two new teaching blocks and the Transmission Hall. South says the project took quite a big hit with the ESFA for using electric. Because measured hot water use by a school is quite a lot lower than the Part L assumption, you can end up in a situation where you pay for a lot of kit to make the production of something that youre not using much of, very much more efficient, with the result that the main cost is then circulating hot water around the school, he explains. Environmental performance data Part of site Existing New Notes On-site installed energy generation 0 0 kWhm per year Design ready for 400kWp array. 31kWhm-2 per yr Heating and hot water load consumption (demand) 88.0 24.0 kWhm-2 per year PHPP predicted energy calculation Total energy load 154.6 67.0 kWhm-2 per year PHPP and TM54 energy calc inc energy consumption. Metering in progress. Carbon emissions (all) 8.1 3.6 kgCO2 m-2per year Uses 30-year projected average carbon factor for electricity. Annual mains water consumption 2.34 2.34 m3/occupant Not calculated. Metering in progress. Airtightness at 50pa 4.1 2.4 m3h-1m-2 As built Overall thermal bridging heat transfer coefficient (Y value) 0.028 0.034 Wm-2K-1 Calculated Overall area-weighted u-value 0.221 0.157 Wm K Predicted design life in years 60 -2 -2 -1 Standard value for carbon and lifecycle calculation 36 November 2022 www.cibsejournal.com CIBSE Nov 22 pp32-34, 36 Houghton school.indd 36 21/10/2022 17:19