As green as it gets

The Green House

Insulation The timber-framed building is made from materials with a low environmental impact, such as locally manufactured bricks and reclaimed tiles. Insulation, in the form of newsprint recycled as Warmcell cellulose, is much thicker than would be expected for a UK building. Heating loss through windows is minimised by argon-filled triple glazing with a low-emission coating. Exploiting natural heat and light To maximise heat and light from the sun, the building faces south. Sunlight enters at a high level, through a row of clerestory windows. These are set at a 60° angle to exploit the winter sun, allowing daylight to penetrate deep into the centre’s interior to illuminate the exhibition space at the rear of the building. Windows set into the wall and lower section of the roof ensure that the classroom, restaurant and entrance lobby also receive sunlight. In summer, external shades shield the lower windows, while internal blinds blanket the high-level glazing. All-year hot water A variety of technologies heat the centre’s domestic hot water. In summer, most heat will come from a dedicated solar water collector. However, additional heating will be provided by passing the air used to cool the photovoltaics through an air/water heat exchanger. In winter, especially on cloudy days, the biomass boiler will provide heat. Internal finishes To stop the building from becoming too hot in the summer, heavyweight materials have been selected for the internal finishes. A mixture of unpainted concrete blockwork or fairfaced brick form the inner leaf of the walls, and the precast concrete floor has a clay-tiled finish. On a hot day, these materials absorb and store heat, and then release it at night, allowing the building to act as a giant storage heater. Heat provision In winter, the centre’s heat losses are so low that it can be heated simply by providing warmed fresh air. On a sunny day, heat is provided by collecting the air warmed by ventilating the photovoltaics and from a set of solar air heaters. Once filtered, this air is ducted into the building. On cloudy days, the waste wood boiler is used to heat the air. To prevent heat waste, air exhausted from the building passes through a heat exchanger. Supplying the centre’s water needs Rainwater collected from the roof supplies all the centre’s water needs. The water is stored in a large tank buried behind the centre, where it is filtered and treated before being pumped to separate tanks on the roof for storage as drinking water and general use. Waterless urinals, low-water flush and composting toilets help minimise water demand. Waste water is collected in a tank where it is treated using bacteria before it is transferred into local water courses. Cooling a hot building The design team was concerned that the expanse of glass facing the sun would make the building too hot. The solution was to make the building perform like a chimney to ventilate the interior: as the hot air rises, it escapes through a row of high-level vents and draws in cooler air through low-level louvres. Generating electricity Electricity is derived from two sources: a wind turbine set away from the building at the edge of the park, and photovoltaic panels. The turbine is expected to generate 12 000 kWh of electricity annually, while the 34 m² of photovoltaic panels on the lower roof will supplement the turbine by supplying an additional 4100 kWh of electricity a year. The photovoltaic panels are ventilated to keep the cells cool and improve their performance. Increasing thermal mass The back of the building is protected by an earth bank, which adds to its thermal mass and provides heat insulation to the building’s cooler north-facing elevation. Inside, the architect has arranged for the intermittently used areas – toilets, stairs and stores – to nestle against this wall so that their heating needs will be reduced.