Insulating your roof
As much as 20% of your energy bill can be saved by good loft insulation. The recommended depth for mineral wool insulation is 270mm but other materials need different depths. Loft insulation can be done by either a contractor or DIY. Mineral wool (such as Rockwool or Rocksil), fibreglass and recycled paper products all work well.
Remember to wear a facemask, goggles and protective clothing if you do it yourself, and leave sufficient gaps around the eaves to avoid condensation. Do not insulate under water tanks that may freeze and make sure that all pipework and the loft hatch are insulated.
Insulating your walls
Most heat (up to half the total) is lost through the walls of an uninsulated house. Wall insulation can reduce this loss by two-thirds and make your home more comfortable. If you have cavity walls, they can usually be safely filled with insulating fibre, beads or foam. If the walls are solid, internal insulation (for example WHISCERS, which is applied in the form of an insulated board fixed to the wall) is highly effective, but it does mean that rooms have to be redecorated and may lose their architectural detail. Internal wall insultation can be done by competent DIYers and can be done on a room by room basis - for example, at the same time the home is redecorated. Solid walls can also be insulated - both internally and externally - but external insulation might need planning permission and should only be carried out by specialist companies.
Insulating your windows and doors
Draughts are the most uncomfortable and obvious signs of a badly insulated house. However, they can be fixed easily with either draughtproofing, secondary or double glazing. Don't be tempted to save money by fixing cheap foam draughtstripping, as it will only last a couple of years before it becomes permanently compressed. Polypropylene tubes are a little more expensive but last longer and are more effective. Remember NOT to add draughtstripping to a room with either an open fire or a gas fire that does not have a balanced flue, where there is no airbrick near the fire. Fires need a good flow of air to burn safely and there is a danger of being poisoned by carbon monoxide fumes if a room is too tightly sealed.
Double glazing is the UK's most popular energy-saving measure, although it actually saves less from a typical fuel bill than putting in (much cheaper) cavity wall insulation. If your windows need replacing, make sure that you specify "Low-e" glazing, which has a special heat-reflective coating between the two panes of glass. This will reduce heat loss through the glass by nearly half. You can also ask for Argon gas-filled windows. Argon is a gas found naturally in ordinary air, but it transmits heat much less readily than the other gases so helps you save even more money. Finally, look at the air gap between the panes; 6mm or 8mm are not really adequate, but 12mm to 20mm are much better at stopping heat losses and reducing noise. Triple glazing is becoming increasingly popular.
Insulating your floor
You can lose as much as 10% of heat through uninsulated floors. There are a number of ways of solving this problem, including insulating blankets under suspended floors and laying boards over concrete floors. Ask an energy advisor for details.
Further information about insulating your home is available from the Energy Saving Trust.