Energy efficient home extension shapes

Overall form

Homes and home extensions take many forms. They contribute to the rich architectural variety we find in our villages and towns. However, when planning an extension it is important to bear in mind that some forms are inherently more energy efficient than others.

The most efficient forms reduce heat losses by reducing the ratio of heat loss area (i.e. the area of exposed walls, roofs and floors) to floor area.

Unless the site dictates otherwise, it is a good idea to make the extension as compact as possible. A two-storey extension is inherently more efficient than a single-storey extension.Very elongated or elaborately shaped extensions should be avoided (as far as possible) because they will result in more heat loss and thus higher heating costs per unit of new floorspace.

For the same reason, it is advisable to avoid very complicated shapes involving wings, bays, dormers, etc. Where the form of the extension is unavoidably complicated, consider adding extra insulation to compensate for the additional heat losses.

An extension with some south-facing pitched roof will permit the use of renewable energy technology such as solar water heating or photovoltaic (PV) panels to generate electricity. These will significantly reduce carbon dioxide emissions.The capital cost of solar PV systems are quite high but falling steadily.The cost of installing solar PV can also be recouped through reduced fuel bills and by selling surplus generated electricity to your electricity supply company (via a ‘net metering contract’).