Typically, you can lose about 10% of your heat through windows and doors. Installing double glazing will reduce this heat loss and keep your home warmer as well as reduce your heating bills.
Double glazed windows have two sheets of glass with a gap of about 15 mm between the two which forms an insulating layer. The window frame material is commonly plastic, but you may wish to choose timber for aesthetic or environmental reasons.
Modern double glazing installations use a low emissivity glass, which has a metal coating on one of the internal panes of glass, inside the gap, to cut down heat loss. To improve efficiency, the gap is filled with an inert non-toxic gas, usually argon. Over time this gas escapes, and after about 20 years when about 25% of the gas has been lost, the thermal insulation of the windows may be impaired. At this point you could consider either replacing the windows or adding a secondary glazing layer.
If your house is a listed building or lies within a conservation area, it is advisable to check with the local authority on any restrictions that may apply to alterations.
You can find a good double glazing installer through either of the following bodies:
- The Fenestration Self-Assessment scheme (FENSA);
- The Double Glazing and Conservatory Ombudsman scheme (DGOS).