Cavity wall insulation consists in filling the wall's air spaces with a porous material like rock wool or glass fibre wool. This traps the air within the cavity and reduces the amount of heat lost by the convection off the wall by 35%.
Cavity wall insulation therefore reduces the cost of heating bills as more of the heat is used effectively. However fitting cavity wall insulation is often only the first step towards a more energy efficient home.

Fitting double glazing to a house will also contribute to fighting off the cold and reduce the house's energy bills. Considerable amounts of energy can be saved on a house that is fitted with double glazing and cavity wall insulation; with certain types of double glazed windows being able to reduce heat loss by up to 90%.

Double glazing windows consist of two panes of low emission glass that are covered with a thin coating of metal in order to reflect thermal radiation and inhibit its emission, therefore reducing heat transfert.The heat from the sun is retained within the building by the air space between the two glass panes.

This effect is known as the solar gain because the heat from the sun is retained by the double glazing window.

This also reduces means that heating bills are considerably reduced because since the heat is retained inside the building as a consequence of the solar gain, there is less of a need to have the central heating turned on for long periods of time.

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