Cavity Wall insulation

Cavity wall insulation

Cavity wall insulation is one of the easiest and cheapest ways to reduce energy costs and CO2 emissions - and improve warmth and comfort.

Why insulate?

Cavity wall insulation can stop a third of your heat loss, keep warm air out of your home in the summer, reduce your carbon emissions and cut your heating bills. When a house is heated, the heat automatically flows outside of the building through the structure. Insulation slows down this process, reducing the rate at which heat escapes by putting an obstacle in its path. Without insulation, your home could lose heat up to three or four times faster.  Insulation can also reduce condensation inside the home because the walls themselves are warmer.

Is my home suitable?

If your home was built after the 1920s and not within the last 10 years (in which case it will probably already be insulated) it is likely to have a gap in the walls of at least 50mm (a cavity) which can be filled with insulation. The brick pattern of cavity walls is usually regular with all bricks facing in the same direction. Before installation takes place, an installer will carry out an assessment to ensure your home is suitable. This assessment will check for wall exposure (from wind driven rain), existing damp (cavity wall insulation could make this worse), that there are no cracks in the walls and the pointing is in good condition, that the cavity is clear and that vents or flues will not be blocked by insulation.

How much could I save?

Cavity wall insulation typically saves you around £115 per year.  The monetary and carbon dioxide savings will depend on your own choices including how long you have the heating on for, how hot you have your house in winter, which fuel you use and how much you pay for your fuel. The Government, the National Insulation Association and the Energy Saving Trust agree on the estimated figures below that are based on a standard, gas central heated, three bedroom semi-detached house:


Rock or glass wool fibre or insulation beads are blown through small, 22mm holes which are drilled at intervals in the mortar joint of each wall. Holes are made good after each injection which are made in turn starting from the bottom. The drilling process does create some vibration and dust so homeowners are advised to remove any ornaments and pictures from the walls. The installer will need access into the property to carry out tests once the installation is complete and also to gain access to any walls of attached buildings, such as garages.