Most older UK homes have suspended timber floors-that is timber boarding with a space beneath. This underfloor void has to be ventilated in order to control dampness and avoid rot in the timbers. The space is therefore draughty and cold (see the Mistergreen blog on filling gaps in timber floors). Timber floors can be insulated by lifting the floorboards and fitting insulation between the joists. The insulation  can be either quilt (as used in lofts), supported on netting draped over the joists or rigid insulation cut to fit between the joists

TIP: put nails at intervals in the sides of the joists at the appropriate depth to support the insulation. This job is usually done if the floor is to be re-covered with carpet, or if the floor is to have a new hardwood floor laid as it is very dificult to relay old boards to a neat finish.

If solid concrete floors are to be insulated, the insulation goes under the concrete or under the leveling screed. Rigid insulation boards are laid and they must be an appropriate grade for laying under concrete floors or they may compress. Get advice from one of our listed suppliers.