The energy we consume in our homes makes up about 25% of UK CO2 emissions. A lot of this is energy is wasted, and insulation is one way to help avoid many tonnes of carbon emissions.
Energy saving measures will also save money on fuel bills, and making homes more comfortable and healthy - by reducing draughts, damp and condensation. Insulation of roof and loft spaces, walls, and floors together with draught proofing measures, energy efficient glazing for windows and insulating tanks, pipes and radiators can make a huge difference. Adding loft insulation and cavity wall insulation can reduce heat loss in a typical British house by 25% which translates to a 40% reduction in heating consumption (Mackay, 2009 p142).
Insulation materials work mainly by trapping small pockets of air – air is actually quite a good insulator in itself, but problems arise when the air moves, taking heat with it. This means that alongside installing insulation you should deal with draughts as far as possible. Although some materials give better insulation than others, a good general rule of thumb is “the thicker the better”.
There are a number of measures of insulation effectiveness. The most commonly quoted in manufacturer's literature are:
- Thermal conductivity (sometimes called k or λ): the rate at which heat flows through a particular material – good insulators have low thermal conductivity.
- Thermal resistance (sometimes called R): the capacity of a given thickness of a particular material to resist the flow of heat – good insulators have a high thermal resistance.
- U-value: the rate at which heat flows through a building element (i.e. a U-value can apply to a sandwich of different materials, such as a wall or a window) – a good window or wall, roof or floor structure will have a low U-value.