Sustainable concept Langley Academy is a model for best
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Sustainable concept Langley Academy is a model for best practice in sustainable architecture and the building itself forms part of the learning experience – it is designed as an active tool to educate children about the environment in which they live and to raise awareness of issues such as global warming. This central theme is introduced on the approach to the building, where the external lighting columns each support a small photovoltaic panel. Inside the school the plant room, ducts and pipes are exposed, so that students can actually ‘see’ how the building works. It demonstrates science in action: in the atrium there is a glazed wall into the plantroom, inside which digital displays show water consumption, energy delivered by the ground source heat pump and roof-mounted solar panels. A three-storey central atrium provides the assembly space for the 1000 students. Here, three elevated two-storey high bold yellow drums, house the science laboratories, which can be glimpsed throughout the building and are a constant reminder of this focus on scientific endeavor. Built largely from sustainable materials, the Academy has been designed with a view to improving its energy performance as it matures and it has the infrastructure in place to add further sustainable and energy-saving measures. A post- occupancy evaluation will also be undertaken. Passive measures The approach to energy usage is holistic and, from the outset, the building has been designed to reduce demand through passive measures, such as exploiting the thermal storage properties of exposed concrete mass to reduce summer time over-heating. Langley Academy is an innovative variant on the ‘π’-shaped building. It is orientated east to west to reduce solar gain and optimise natural ventilation, maximising natural ventilation for most teaching spaces and drawing daylight deep into the building – darker spaces are southerly oriented, while rooms requiring more daylight look north. Externally, horizontal solar shading reduces solar gain in south-facing classrooms while vertical shading on the east- and west-facing glazing provides shade in the mornings and evenings. The lightweight steel roof is supported on cellular beams that provide a route for the exposed services and it incorporates large roof lights. The building’s concrete floorplates and roof slab exploit the attenuating properties of thermal mass to limit summer temperatures, while providing acoustic insulation between floors. Classroom depths are proportioned to maximise natural ventilation and daylight. The teaching spaces open onto enclosed streets that aid natural ventilation – inside the classrooms a low strip of windows ‘inhales’ cool air, while higher windows ‘exhale’ the warm air as it rises. The lower vents are manually controlled and the upper vents opened by an actuator under control of the building management system, which can be overridden by the teachers. Active systems To establish the exact glazed area necessary to reach a minimum daylight factor of 2%, the design team used computer modelling. Where artificial lighting is required, there is a series of linear uplight/downlight fittings, with separate circuitry and switching for the external perimeter row of luminaires. Classrooms where noise could be a problem when both sets of windows were open, such as language laboratories, have mixed-mode ventilation. They still have manually opened lower windows and actuator-controlled upper ones, but also benefit from simple high-level extract ventilation. Heat in the exhaust air from the mixed-mode classrooms is captured by a heat exchanger and used to heat the atrium. The air for spaces such as the music rooms and metalwork rooms is supplied from one of eight roof-mounted air-handling units and cooling is provided by a roof-mounted air-cooled chiller. Mechanical ventilation is also used for the sports hall, lecture theatre and drama studio on the west of the building. The energy strategy makes use of on-site renewables, which include a ground source heat pump, a biomass boiler, solar thermal panels and photovoltaics. A 300kW biomass unit acts as lead boiler for the low temperature hot water system feeding the perimeter radiator system, providing 58% of the total energy requirement. It consumes about 230 tonnes of woodchip a year, sourced locally to maximise carbon savings. Roof-mounted, gas-fired condensing boilers provide backup and supplement the biomass boiler at times of peak demand. Estimated carbon savings compared to a typical academy is 131 tonnes annually. A 45kW closed-loop ground source heat pump, fed from eight 108m-deep boreholes, provides low-grade heat to the underfloor system in the atrium and restaurant areas, while on the south-facing roof, 40m2 of solar thermal collectors, connected to two roof-top thermal stores, pre-heat the domestic hot water. Water As part of curriculum activity, students will be able to study water conservation. The roof is designed so that rainwater can be collected and stored into a central tank. The Academy is designed to use 30% less than conventional schools. Grey water, the dirty water from washing, washing up and showers, amounts to over half of a school’s wastewater, so the building has a separate pipe system that collects this for recycling. Rain water harvesting significantly reduces the use of drinking water for non-potable purposes. Rain water is used to flush 18 of the toilets and the grey water is filtered and used in irrigating the plants, watering lawns and cleaning the windows. Sanitaryware in each of the teaching units is fitted with low flush toilets and push-button taps so that the students will be able to monitor water usage and make comparisons, which can form part of the curriculum teaching. During the first academic year, of the 83,000 litres of water consumed, only 16,000 litres was from the mains.