Sustainable schools

During the recent heat wave, schools reported classroom temperatures in excess of 360C, with both teachers and pupils suffering from heat exhaustion. However, proper use of the school buildings' thermal mass could have significantly reduced the internal ambient temperatures without having to install

energy-intensive and expensive air-conditioning systems. This approach is advocated by both the Chartered Institution of Building Services Engineers (CIBSE) Technical Memorandum 36 which highlights the need for solar shading, ventilation and thermal mass to combat overheating - and the Department for Education and Skills (DfES) Building Bulletin 101 which states: 'Summertime overheating can be largely eliminated by the provision of sufficient ventilated thermal

Thermal mass capacity

Unlike other building materials, concrete has a high thermal mass capacity. Concrete acts as a thermal sponge, absorbing heat during the day and so cooling and moderating the daytime peak temperatures. The stored heat is released at night in readiness for the next day. This moderation of peak temperatures is called fabric energy storage (FES). This is a natural process that minimises the need for energy-intensive airconditioning with all its resultant carbon dioxide emissions.

About 90% of the environmental impact from buildings is from heating, cooling and lighting. Only some 10% is from the embodied energy used to produce the material of the building's structure. Using energy-efficient FES to reduce internal ambient temperatures will decrease both a school's environmental impact and its energy bills.

The predictions are that climate change will result in hotter summers. Therefore, it would seem prudent to design and build schools to incorporate adequate ventilation and solar shading and to make use of thermal mass to avoid classrooms overheating and avoid the necessity for air-conditioning.

Sustainability and adaptability

Sustainability is about more than reducing energy consumption - it is also about ensuring the successful future use of buildings. Flexibility and adaptability are key design requirements for any school. In the short term this may mean simply rearranging furniture; in the long term it could involve moving internal walls. Extended linear room plans allow efficient modification of room sizes and functions over the life of a school. For example, adaptability can be built in, with three 60m^sup 2^ classrooms that can be changed to one of 70m^sup 2^ and one of 110m^sup 2^. Basing school layouts on columns with no beams using a flat soffit concrete slab provides a total flexible design solution and gives greater future adaptability of services. With classroom sizes a key issue, concrete crosswall solutions, offering large openings of up to 75% of the width of the classroom, allow flexibility in joining classrooms.

Alternatively, floors can span right across rooms between walls on the fa?ade and/or corridor lines. This gives the possibility of using load-bearing cladding panels, which comprise a load-bearing inner wall, insulation and an external decorative finish. These can be factory-made or site-cast horizontally and tilted or lifted into position. Speed of construction is greatly enhanced when the insulation and cladding are installed with the structure. Meanwhile, for services and future stairs or lifts, holes in both normal and post-tensioned concrete slabs can easily be designed-in and formed during construction or cut out later as required.

Concrete is material of choice

A new report has emphasised the importance of sustainability for school buildings. Here, the inherent thermal efficiency of concrete and its ability to allow buildings to be easily adapted for future changing requirements puts concrete at the top of the class.

The report, Procuring the Future, from the Sustainable Procurement Task Force, led by former Carillion chairman. Sir Neville Simms, singled out the Government's ?40 billion Building Schools for the Future programme as an opportunity for the Government to make a difference. It called for 'the Treasury and the Department for Education and Skills to work with the programme to ensure that it is meeting high sustainability standards'.

Concluding remarks

The Government has stated that it plans to make all government buildings carbon neutral by 2012 and cut emissions by 30% by 2020, and Procuring the Future believes that the major schools building programme being implemented should play an important part in achieving that. Concrete construction can significantly contribute to the sustainability standards being called for.