Greenhouse effects: Wall insulation

Tony Juniper
As the leaves turn gold, red and brown, and summer fades into memory, many of us will put on the heating. It may keep us comfortable, but heating causes about a third of our greenhouse-gas emissions. If your home is not well insulated, much of this heat is lost — which is a waste of money as well as energy.
In an uninsulated home, up to a third of the heat loss can be through the walls, so this is a good place to start. While older homes tend to have solid walls, those built after the mid-1920s are likely to have cavity walls — two layers of brick or blocks with a space between them. If you are not sure what type your home has, try measuring the thickness of the wall at a window or external door. Cavity walls will be at least 26cm thick. Brickwork with all bricks laid “side on” also indicate a cavity.
Building regulations specify that all homes built since about 1990 must have cavity walls insulated, but this doesn’t cover older homes.
In many cases, you can retro-fit insulation, but to establish whether this is possible — and whether additional ventilation is required — you will need a survey.
You cannot do the work yourself, so will need a properly registered installer. The Energy Saving Trust recommends choosing a member of at least one of these groups: the National Insulation Association, the Cavity Insulation Guarantee Agency and the British Board of Agrément. Each has a website with a list of registered installers — click on the links at energysavingtrust.org.uk.
To improve insulation, the cavity in the wall is filled with material such as mineral fibre, polystyrene beads, foam or glass, usually inserted through small holes drilled in the outside wall. This stops heat passing through the wall. Most companies charge about £500, but grants are available to all householders to cover 50%-100% of the cost (for details, visit government-grants.co.uk).
The investment should pay for itself within two or three years, while the bonus of lower heating bills will continue for many years to come — as will the environmental benefit.
If you don’t have cavity walls, don’t despair. There are ways to improve the insulation of solid walls, too, but they are for a future column.
Tony Juniper is an environmental campaigner and former director of Friends of the Earth; tonyjuniper.com