Cavity wall insulation reduces heat loss through walls by up to 60%. It is a quick process taking only 3 to 4 hours to install. It is cheap to install and is achieved by injecting fibre, polystyrene bead, or foam into the cavity. This involves drilling small holes in the brickwork from the outside and injecting the insulation to fill the cavity. An investigation will first be made to confirm the cavity is within certain tolerances to accept the insulation proposed. Grants from utilities (CERT grants) for cavity wall insulation have reduced costs to around £200 to £350 for the majority of homes and in certain circumstances may be free.
Where there is no cavity or it is not suitable for filling, external or internal wall insulation are the only options.