Constructing low energy buildings

There are some basic rules of thumb for constructing environmentally friendly housing: maximize energy efficiency, limit the project's impact on the surrounding environment, and recognize that small can be beautiful. In choosing building materials, environmentally friendly materials, certified timber and recycled products can all be utilized within energy efficient designs.

In many countries about half the commercial energy supplied is used to heat the spaces in which people live and work. Such heating is often highly inefficient for reasons such as poor insulation standards and poor controls that ensure that heat and light are supplied only when people need them. Building energy efficient homes can lead to both substantial energy savings and benefits for the environment.

100 low energy houses have been built in a village near the Hague by the Netherlands Agency for Energy and the Environment (NOVEN). The houses have an energy consumption of 10% of conventional houses. 4,000 low-energy houses are planned in the new city of Amersfoort.

The framing, roof, and siding of a building can be made from recycled-content steel: old soup cans, car bodies, and junked appliances transformed into steel studs, siding, and roofing.

In most conventional homes the interior walls are sheathed with gypsum wallboard which comes not from a mine. An alternative source comes from the pollution-control devices that "scrub" sulphur dioxide gas from the smoke of coal-fired electric power plants. (The scrubbing process combines water and lime with the sulphur gas, producing, in the case of a large power plant, a million or more tons annually of a wet slurry of synthetic gypsum, perfect for wallboard.) The sandwich of paper that lines the gypsum into wallboard is made from recycled paper.

Low-odour, low-solvent paints are now available from many major manufacturers. Such paints, which reduce both indoor air pollution and outdoor smog, are often labelled as "low-VOC," or low in volatile organic compounds.

Trex, is a combination wood-polymer "lumber," made from recycled plastic grocery bags, ground-up wooden shipping pallets, and scrap wood from furniture factories.

The award-winning energy efficient house, presented at a FutureWorld exhibition in 1994, uses a simple convection system that incorporated a two-storey glass conservatory covering the south wall of the house. Air is heated inside the conservatory and rises to be either drawn into the house using a low-power fan or allowed to escape through windows in the conservatory. Cooler air is drawn in through air bricks in the northern wall and passed under the house by convection. It is either cooled further or heated depending on the soil temperature under the building. Deciduous vines planted inside and outside the conservatory provide shade in the summer and inhibit over-heating. Solar panels in the roof heat water for washing and the underfloor heating system. Supplementary heat is provided by an oil-fired boiler. The house was built using concrete block, brick and a timber cladding. The 150 mm blocks assist insulation. Sensors embedded in the walls allow a sophisticated computer system to control the blend of natural and man-made heating. The thick walls, combined with the natural convection flow of the building, help to prevent condensation and damp.

Well-equipped electronic offices for working from home are potentially the greatest energy-saving feature of any energy efficient house.