Primary school breaks new ground in working with the environment
Taking the application of ground-source heat pumps a significant step forward by collecting and storing energy from the Sun during the summer and using it for heating in the winter is a new school in Hertfordshire.A new primary school in Hertfordshire is believed to be the first building in the world to feature a heating system that uses the school playground to heat and cool its buildings. Commissioned by Hertfordshire County Council, designed by a Capita Architecture led consultant team with project and construction managed by Mace, the Howe Dell School in Hatfield is a beacon project for Hertfordshire County Council. It could now have a major role to play for schools built across the world as a demonstration of how sustainable practice can be integrated into building design. Falling within the Government’s ‘eco schools’ strategy, Howe Dell features low-energy buildings and a host of renewable energy technologies, which will soon include a wind turbine capable of exporting surplus electricity production to the National Grid. Over the life of the project, the school has integrated sustainable principles into an ‘eco curriculum’ that has been rated as outstanding by Ofsted inspectors. Building-services consultants Fulcrum Consulting were pivotal in the development of sustainable features within the building, assisting in the integration of the new heating system — interseasonal heat transfer (IHT) — as part of the innovative environmental design. The IHT system has been invented and developed by ICAX Ltd (Interseasonal Collection & Exchange). It captures heat energy from the Sun via a pipe network just beneath the surface of the school playground. This energy is stored in computer-controlled ThermalBanks in the ground under the school and released to heat the buildings in winter via a series of heat exchangers linked to both the underfloor heating and a TermoDeck system (a heating/cooling and ventilating system that uses the structure of the building to stabilise the environment).
Pioneering the use of a new approach of gather solar energy during the summer and storing it for use during the winter — Howe Dell School in Hatfield, Herts. In addition, ‘coolth, collected during the winter can be used for cooling in the summer. (All photos: Peter Durant)
The temperature of the ground at a depth of 7 m in the UK will normally be around 10°C, and it will vary little between summer and winter as heat moves only very slowly in the ground — about a metre a month. Using water as a transport mechanism solves the difficulty of getting heat into the ground — and out again. The pipe network is below the playground, and the surface temperature of Tarmac can often reach 15°C higher than the ambient air. Using interseasonal heat collection and exchange, the temperature of the ground below the insulated foundation of a building can be increased from its natural temperature of 10°C to over 25°C during the summer. Such a high temperature give a heat pump a much higher COP. The system can also store ‘coolth’ in the winter and use it to cool the building in the summer. £244 000 of grant funding was awarded for the project by the Carbon Trust as part of its mission to develop commercially viable low carbon technologies. Howe Dell was designed by a team from Capita Architecture’s London office — with input from staff, pupils, parents and governors. The school has also been awarded ECO Green Flag accreditation (the highest level of award granted by the UK’s eco-schools programme) and will act as a learning resource for its pupils and the wider community. The school provides education for children up to the age of 11 and also incorporates nursery provision, a day-care facility for children from the age of six months and a community centre that can provide a range of after-school learning courses for local adults, among other traditional community uses. The school has earned plaudits from the BREEAM environmental assessment method for buildings and was selected as one of eight projects used during the development of the new BREEAM for schools initiative. Preliminary appraisal by the pilot assessment panel for the school showed that its innovative design achieves a level equivalent to the highest BREEAM rating, making it one of the highest achieving pilot schemes. The school also incorporates many other sustainable elements. They include the use of recycled and sustainable materials, natural ventilation, energy-saving lighting and water management. In addition to the IHT renewable-energy system, the school has solar thermal collectors to pre-heat water for the school kitchens and washing facilities and photo-voltaic panels to generate electricity.
Heat collected from just under the playground of Howe Dell school during the summer is stored in a ThermalBank under the school to provide a relatively high-temperature energy source for heat pumps during the heating season.
An easily accessible, school-wide software interface allows pupils to monitor the various environmental systems and help them understand how energy has been generated by the various systems, how it is being stored and how much has been exported to the National Grid. Visitors to the school can see real-time energy data displayed on an screen within the main school entrance. A TermoDeck fan-assisted heating, cooling and ventilation system uses the thermal mass of the structure to stabilise the temperature in the building. Strategically placed rooflights allow natural daylight to flood into the centre of the building, minimising the need for artificial lighting of deep plan spaces. Living sedum green roof areas helping to manage water runoff, insulate the building and promote bio diversity. All aspects of the roofing, including the roof lights and green roof, were managed by Letchworth Roofing Company. High performance windows reduce heat loss and help control solar gain. Light wells bring natural daylight into the ground-floor corridors. There is a sustainably sourced sprung timber floor in the main hall and a bamboo floor in the dining room. Classroom sink tops and splash backs are made from recycled yogurt pots. Play equipment is made from sustainably sourced timber. A simple rectangular shape enables all teaching areas — which all face south — to have dedicated external classrooms, allowing pupils direct access to the extensive and bio-diverse grounds.
Both solar thermal and solar photo-voltaic collectors are used at Howe Dell School.
Rainwater harvested from the main school roof is used primarily for toilet flushing, with any surplus being used by the irrigation system or to top up for the wet-land biodiversity area located within the school grounds. Headteacher Debra Massey explains: ‘Our curriculum has sustainable education principles at its core and we’ve already had a lot of positive feedback from Ofsted. Our “eco squad” of pupils helps promote ideas of sustainability and learning about the environment across the school, enabling us to engage pupils of all ages with the school’s ethos.’ Keith Emsall, executive member for education at Hertfordshire County Council says: ‘This unique project is a resource for the whole community. I strongly believe that if our children can be enthused about the importance of caring for their environment from a very young age, they will carry that message with them throughout their lives. I’m proud that Hertfordshire is setting the benchmark for other authorities with this exciting new building.’ Staff of Howe Dell have also worked closely with the University of Hertfordshire to devise an assessment and research strategy so that the changing attitudes and awareness of staff, parents and children to their environment can be tracked throughout the project. Clare Devine, a director of Capita Architecture, said: ‘Over the last few years, Capita Architecture has designed a number of award-winning buildings along sustainable principles – from pioneering eco-schools to groundbreaking hospitals. The new technologies and environmental design approaches implemented at Howe Dell are a perfect example of how sustainability in design and construction is continuing to advance rapidly. It really is an excellent example of how sustainable principles can play a vital role in terms of both building design and the children’s education.’ Robert Trezona, head of research and development at The Carbon Trust, said: ‘The application of Interseasonal heat transfer technology can significantly reduce a building’s need for heating fuel and provide considerable carbon emissions savings. By awarding Howe Dell School a £244 000 grant as part of our Applied Research scheme to demonstrate the concept, The Carbon Trust is helping to speed widespread commercialisation of this low carbon technology.’ For more information in the ICAX ThermalBank system put
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