Cavity Wall Insulation
Buildings constructed after about 1920 are likely to have external walls which are made up of two layers with a gap or cavity between them. Cavity Wall Insulation fills that gap with a highly insulating material which helps reduce heat losses by up to 40%. Benefits include reduced fuel bills, a warmer building with fewer draughts, reduced condensation, and lower carbon emissions. Payback times will be under 3 years
During the installation process, a number of holes are drilled through mortar joints and insulation material is injected to fill the cavity. The types of cavity wall insulants used include mineral wool (e.g. rock wool), beads or granules (e.g. expanded polystyrene beads) and insulating foams (e.g. polyurethane).
It is possible to determine whether a brick wall has a cavity based on the arrangement of the bricks in the wall.
Figure (a) shows a brick wall, typically constructed before 1920, which does not have a cavity. If you wish to insulate a wall of this type you will need solid wall insulation in the form of external or internal wall insulation.
Figure (b) shows the arrangement of the bricks in a wall with a cavity.