How to Insulate Walls and Floors
The walls of any house represent a huge part of the building and it is essential that they are well insulated. The type of insulation required depends on the fabric of your home – solid walls require one method, cavity walls another. It is also imperative to insulate your home at ground level, as around 15 per cent of heat can escape through the floors.
Heat loss in walls
The largest area of heat loss, some 35 per cent, is estimated to escape through house walls. However, the best solution, which is cavity-wall insulation, is a job that must be left to the professionals. Despite the extra outlay, the work is very cost-effective, and you can expect to see a return on your investment after a few years. This treatment, of course, is not possible if the house has solid walls. The usual procedure is to pump foam, pellets or mineral fibres into the cavity through holes drilled in the outer leaf of the wall. Make sure that the work is carried out by an approved contractor.
Applying insulation to the inner faces of walls is well within the scope of most people. One possibility is to use thermal plasterboard (gypsum board) to dry line external walls. Another is to add a timber framework to the wall, infill with slab or blanket insulation and face it with plasterboard. To prevent condensation, plastic sheeting should be stapled to the insulating material.
The disadvantage of both of these methods is that you will lose some of the floor area of the room. At least 50mm (2in) will be lost by using thermal plasterboard, and more if you create a new partition wall. However, in terms of comfort and cost-savings, this sacrifice may be worth making. Providing the plaster wall is sound, the boards can be fixed directly to it with adhesive. A vapour barrier is included as standard.
If you draughtproof floorboards that have substantial gaps, bear in mind that it could involve disruptive work and should be avoided if possible. If you are prepared to lift and replace floorboards, the methods are very similar to laying roof insulation.
However, you will need to provide some means of supporting the insulation material between the joists. Nylon netting stapled to the sides of the joists is the usual method for holding glass fibre insulation blanket in place. Pull up the netting tightly before nailing down the boards so that the blanket does not sag and let cold air through. Lengths of wood fixed between the joists will support slab insulation.
An easier method of coping with a draughty floor is to choose a good underlay for your carpet and also repair any gaps or cracks between floorboards with sealant.
Larger gaps will need to be filled with strips of wood, carefully cut to fit tightly. Spread adhesive on the sides of each strip and tap it into the gap. Allow the glue to set, then plane down the strip so that it is flush with the surrounding floor.
Solid concrete, or direct-to-earth, floors are generally insulated by covering the area with sheets of rigid polystyrene, topped by a covering of polythene sheeting. A floating floor, comprising of tongued-and-grooved chipboard, is then installed over this.
A gap of 9mm should be left between the chipboard and the wall to allow for expansion. This gap will not be noticeable once a new skirting (base) board is installed. The layer of air trapped under the floating floor will help keep the area warm.
This work can be fairly disruptive, and as the new floor will be at a raised level, existing doors will need to be removed and planed down. Architraves (trims) around doors will also need to be shortened to accommodate the change.