Cavity wall insulation


Around a third of all of the heat lost in an un-insulated home is through the walls. Insulating cavity walls reduces heat loss and can save you around £110 a year on your fuel bills. Cavity wall insulation can also help to reduce condensation inside the house if it is a problem on external walls.


If your home was built before or around 1920, its external walls are likely to be solid rather than ‘cavity walls’. Cavity walls are made of two layers with a small gap or ‘cavity’ between them. This cavity acts as a barrier to reduce heat flow through the wall. Solid walls have no such gap and this allows more heat to pass through them than through cavity walls. In fact, twice as much heat can be lost through an un-insulated solid wall as through an un-insulated cavity wall. But the good news is that, like cavity walls, solid walls can be insulated – from the inside or the outside.


Solid walls can be insulated in two different ways: with internal insulation (from the inside) or external insulation (from the outside). Both options can make your home warmer and more comfortable and greatly reduce your energy bills at the same time.  Although grants may be available, insulating your walls can be expensive, with internal installation costs varying between £5,500 and £8,500, but you could save up to 40% on your annual heating bills (around £365 per year on average) and 1.8 tonnes of CO2 respectively.


How does cavity wall insulation work?

Heat will always flow from a warm area to a cold one. In winter, the colder it is outside, the faster heat from your home will escape into the surrounding air. Cavity wall insulation slows down the rate at which it escapes, keeping as much of it as possible inside your home for as long as possible. Insulation makes it much more difficult for heat to pass through your walls by filling up the cavity with a material with lots of air pockets in it. These pockets greatly reduce what is known as your walls’ U value – which is a measure of how quickly they lose heat. The lower the U value, the slower heat is lost – and the less energy you need to keep your home warm.


Why insulate your cavity walls?

Cavity wall insulation is an effective way to save energy and money at home. A well insulated house keeps warmth exactly where you need it – indoors. So, insulating your cavity walls will help you to heat your home more efficiently. Using less energy reduces carbon dioxide emissions (CO2) – one of the biggest causes of climate change. Cavity wall insulation can also help to reduce condensation inside the house if it is a problem on external walls.


Benefits of cavity wall insulation:

  • Keeps your home temperature comfortable all year round.
  • Cuts your carbon footprint & greenhouse gases by preventing heat loss.
  • Increases the value and saleability of your home.
  • Reduces traffic noise and other disturbance.
  • Prevents the effects of condensation and mould.
  • Lowers your household emissions.


Grants are awarded on a first come first served basis and funds are limited, so if you don’t apply now, you could miss out.


For more ways to reduce your carbon footprint, visit our Eco Page here. If you’re interested in making your home more energy efficient (and saving money at the same time!) visit Ace’s Tips for all you need to know about boiler efficiency, loft and cavity wall insulation, double glazing, solar electricity installations and general energy saving tips.