If your home was built before the 1920s, its external walls are probably solid walls rather than cavity walls.
Solid walls can be insulated though – either from the inside or the outside. This will cost more than insulating a standard cavity wall, but the savings on your heating bills will be bigger too.
If you have solid walls, then they’re almost certainly not insulated - but the first thing you need to find out is what sort of walls you have.
If you can see the brickwork on the outside of the house, look at the pattern of the bricks as this can show how the wall has been built.
If the brickwork has been covered, you can also tell by measuring the width of the wall. Examine a window or door on one of your external walls.
If you live in a house that has a non-traditional construction such as a concrete, steel or timber-framed building, you will need a specialist installer with experience in insulating your building type to advise you on your options.
Typical installation costs* of solid wall insulation can vary as follows:
*Based on a typical semi-detached house in Great Britain
You might be able to reduce these costs by carrying out the work at the same time as other home improvements or by not tackling the whole house at once.
The costs we suggest for installing solid wall insulation are for paying a company to come in, insulate your whole house in one go, fully redecorate and replace everything just as it was. Some people want exactly this, but it does cost a lot of money. If you're looking to spend less, it is advisable to insulate a wall when you are having other building or decorating work done.
Internal insulation can be fitted when you’re planning to redecorate anyway, or to fit a new kitchen or bathroom. You can also spread the cost by tackling one room at a time.
External insulation will also cost less if you fit it when you're having other work done to the outside. If you're having a new roof, or painting the windows, or even having solar PV panels fitted, then you will probably have scaffolding up already, which can save a bit on the costs. If your walls need re-pointing or other repair work, it’s worth getting a quote for a complete refurbishment including insulation – it will probably work out cheaper than doing the two things separately.
Sometimes there is financial support available to help with the cost of solid wall insulation. Contact your local authority to see if there is any help in your area, or read about financial support in Scotland.
Internal wall insulation is done by fitting rigid insulation boards to the wall, or by building a stud wall filled in with insulation material such as mineral wool fibre.
Find out more about choosing internal wall insulation.
External wall insulation involves fixing a layer of insulation material to the wall, then covering it with a special type of render (plasterwork) or cladding. The finish can be smooth, textured, painted, tiled, panelled, pebble-dashed, or finished with brick slips.
Find out more about choosing external wall insulation.
In traditionally built properties with solid walls, water vapour can usually move quite freely through the building. This is partly because of the high levels of ventilation and draughts, but also because water vapour can travel through the bricks and stones that the walls are made of. When you insulate an older building, you will change the way that water vapour behaves in several ways:
Whenever you fit solid wall insulation to a building you need to take account of water vapour to make sure that you don’t create new damp problems in the future. This may involve using “breathable” insulation materials that will allow the vapour to carry on permeating the walls, or it could involve creating a continuous vapour barrier to make sure no vapour can get into the walls from the inside. You will need an experienced specialist installer to develop a moisture control strategy that is specific to your building.
You should check with your installer that the installation is covered by an appropriate 25 year guarantee. They may be members of the SWIGA guarantee scheme, or they may offer an independent insurance-backed guarantee. You can find a list of Ofgem approved guarantee schemes here.
Does your home have cavity walls that need to be insulated? Visit our page for more information, costs & savings and installers.Cavity Wall
Are you planning other energy efficiently upgrades in your home? See our Home Improvements guide for more information.Home Improvements
You can visit or chat with homeowners who have already installed insulation in their hard-to-treat home using our Green Homes Network (GHN) tool. For a free home visit, call Home Energy Scotland on 0808 808 2282 (Monday-Friday, 8am-8pm and Saturday, 9am-5pm).GHN search