Greening the valley

Everyone, it seems, is designing houses of the future. There are prefabricated houses of the future, electronic houses of the future, and low energy houses of the future. They would all claim to be sustainable in one way or another, but many work to single issue agendas, and therefore bristle with technologies donated by media-hungry industry sponsors.

This prototype house of the future aims to be different. Sustainability, to the architect Jestico + Whiles, means environmental responsibility and long-term flexibility. A true house of the future, the practice argues, should be accessible to all, whether able-bodied, frail or disabled, and be able to respond to an aging population by allowing people to stay in their own home as their mobility decreases.

More specifically, this scheme is the Welsh House of the future – a prototype for future housing design and living in Wales. Jestico + Whiles has designed the house to be built as either a terrace or individual properties. A three-bay example is now under construction on the Museum of Welsh Life site at St Fagans, near Cardiff. It will be lived in for two weeks to test the concepts, after which it will become a visitor attraction for the annual 400 000 museum visitors. The design team therefore had to ensure that it would operate equally well as a house and as an exhibit.

The structure will be of timber frame, with lightweight internal partitions constructed of locally-made clay blocks. This gives great spatial flexibility, enabling the house to be configured as a loft on the ground, or as a five-bedroom dwelling.

This level of flexibility is a reflection of typical Welsh living patterns. There is an option for a granny flat, children's den or a separate sub-let apartment, in various configurations. A wall- climbing through-the-floor lift will allow visitors to access all areas of the house.

Construction materials are being procured locally, and chosen wherever possible for their low environmental impact. For example, timber for the structure is being sourced from local sustainable sources, which serves to reduce embodied energy and keep profits within the local community.

Environmentally-sound engineering was a key design issue for all aspects of the house, and Jestico + Whiles enlisted ECD Energy and Environment to advise on the details.

The large south-facing glazed facade is designed to maximise solar gains, with the 16 mm argon-filled Pilkington double-glazing possessing a U-value of around 1·1 W/m²/K. ECD is undertaking thermal analysis to determine optimum shading and thermal mass for comfort conditions. The designers are also considering the virtues of "variable insulation" – otherwise known as sliding shutters or roller blinds.

The absence of mains gas on the site led the design team to choose a Markus high-efficiency ground-source heat pump, with an EnviroFire pellet fuel stove for the coldest winter days (which again fits well into the historical Welsh context). Domestic hot water will be supplied by a Filsol flat-plate solar collector.

The Swedish-designed heat pump (boasting a cop of around 3·0) will be powered by electricity from renewable sources within Wales, which means that it will have zero net CO₂ emissions. The electricity supplier will be accredited under the Energy Saving Trust's Future Energy Scheme.

About 10% of the electrical load will be produced by a small roof-mounted wind turbine plus photovoltaics. As shown in the diagram above, the 2-3 kW turbine will be installed in a Venturi section of the roof which will serve to concentrate wind power, possibly by up to a factor of three.

The north side of the house is being fitted with an oversized eaves gutter to collect rainwater which will be stored in a 4·5 m³ tank, probably made of reclaimed material. This will be used for watering the garden and wc flushing – the latter relying on HEPA filtration. Water use will be kept to a minimum by the use of low water appliances, showers and spray taps.

The design team is hoping that the scheme will be the first to use locally produced sheep's wool insulation. Roof insulation will also rely on recycled newspaper, produced locally by Warmcel.

Construction started on site in September, with completion due in April 2000. It should prove a worthy visitor attraction, but the design team is playing for higher stakes – a developer prepared to build the house on a commercial basis.