CIBSE AWARD WINNER | STREATHAM AND CLAPHAM HIGH SCHOOL naturally ventilated and passively cooled; we modelled them [in accordance with the methods] in CIBSE TM52 The limits of thermal comfort: avoiding overheating in European buildings to ensure they would not overheat. OR Consulting has exploited an area of pitched south-facing roof that rises over the clerestory window to accommodate a row of photovoltaic panels (PVs). Theres 80m2 of PV, installed as part of our carbon-reduction strategy, connected to the schools electrical infrastructure, with the surplus exported to the Grid, says Roberts. To help pupils and teachers understand how the building works, the design team has placed operating instructions written in what Roberts terms laymans language next to each element. For example: In summer, please open these windows to cool the space; In winter, please keep windows closed to reduce carbon emissions. Once people understand the controls why theyre there and what they do they get more comfortable with their use, says Roberts, who adds that the sixth-form spaces are designed to be mechanically ventilated to prevent the need to open windows in winter. Weve kept the design as simple and passive as possible; it is predominantly a natural ventilation system with heat-recovery ventilation just for the winter. Two large- and three small-capacity MVHR units supply fresh air to, and extract stale air from, the spaces via distribution ducts running at high level in the corridor an arrangement that required careful acoustic detailing: We had to get the acoustic crosstalk details correct to ensure there would be no noise transfer through ventilation ductwork to adjacent classrooms, explains Roberts. Within the spaces, the ducts are concealed Energy benchmark commentary Energy and CO2 emissions have been compared with benchmarks taken from CIBSE TM46, Department for Education (DfE) Technical Annex 2H: Energy, and the projects SBEM predicted consumption. The SBEM predicted energy consumption includes ancillary catering spaces, which act to increase the hot-water usage within the calculation. As such, the SBEM predicted energy benchmark is not a 100% like-for-like comparison. The annual energy consumption for Streatham and Clapham High School are: 59% below the TM46 benchmark 45% below the DfE higher-range benchmark 23% below the DfE lower-range benchmark 21% below the SBEM notional energy consumption (including equipment usage) 11% below the SBEM actual energy consumption (including equipment usage). From the breakdown of energy loads by end use, equipment allowances. Energy usage (kWh.m-2 per annum Energy benchmarks Streatham and Clapham High School SBEM actual energy SBEM notional energy Department for Education energy benchmark lower Department for Education energy benchmark higher TM46 benchmark (schools and seasonal buildings) Exposed CLT gives the schools new dining room a warm, natural look above a series of suspended service rafts, which incorporate lighting, electrical distribution, acoustic panels and smoke detectors. In every classroom, all of the services are integrated into the same element, so you have a polished detail, says Roberts. Heating and IT strategy In winter, roof-mounted air source heat pumps (ASHP) provide heat to the classrooms via an underfloor system. Two heat pumps, rather than a large, single unit, were used to add resilience to the system, and, as Roberts explains: Low-temperature underfloor heating was necessary to optimise the operating temperature of the heat pumps. Stair towers connect the sixth-form centre with the school below, and incorporate new plant areas and a fully accessible passenger lift. The ASHPs are housed in the west rooftop plant enclosure, along with the heating system buffer vessel and one of the heat-reclaim ventilation air handling units. The east rooftop plant enclosure houses the second large MVHR unit, ventilation plant for the new kitchen, and gas-fired hot-water generators selected for their ability to respond to the high, short-term hot-water demand of the kitchen. Between them, the rooftop plant enclosures incorporate most of the plant for the first and second phases of the project. A new riser links the plantrooms to the second-phase buildings, with services capped off at ground level until completion of the 28 August 2021 www.cibsejournal.com CIBSE Aug 21 pp26-28, 30 Collaboration award.indd 28 23/07/2021 12:09