Cavity Wall Insulation Calculator
Estimate the installation cost, annual energy savings, and payback period for cavity wall insulation in the UK. Compare materials and see your CO2 reduction.
Cavity Wall Insulation Estimator
Calculate expected costs and energy bill savings for your home
Select the type of property you own
Larger properties have more external wall area and cost more to insulate
Standard mineral wool is the most cost-effective. Premium materials offer better performance for damp-prone walls.
Your current fuel type affects how much money you will save on your energy bills
Insulation Cost & Savings Result
Estimated Installation Fees & Energy Bill Reduction
Enter your property details and click Estimate Costs & Savings to see your expected installation costs and annual energy bill savings.
Cavity Wall Insulation Costs by Property Type
Typical installation costs in the UK for 2026 based on average property sizes and standard installer rates. Prices vary based on exact wall area, accessibility, and local labour costs.
| Property Type | Mineral Wool | EPS Beads | PU Foam | Annual Savings (Gas) |
|---|---|---|---|---|
| Flat (1-2 Bed) | £500 | £650 | £800 | £120 |
| Mid-Terrace (2-3 Bed) | £750 | £975 | £1,200 | £200 |
| Semi-Detached (3 Bed) | £850 | £1,105 | £1,360 | £250 |
| Detached (4 Bed) | £1,100 | £1,430 | £1,760 | £350 |
*Estimates based on standard UK locations and average wall areas. London & South East prices may be 10-15% higher.
Cavity Wall Insulation Costs & Savings FAQ
Everything you need to know about cavity wall insulation costs, energy savings, and the installation process in the UK.
In 2026, the cost of cavity wall insulation in the UK typically ranges from £500 to £1,800, depending on the size of your property and the material used. For an average 3-bedroom semi-detached house, you can expect to pay around £850 for standard mineral wool insulation. Premium materials like EPS polystyrene beads or polyurethane foam can increase the cost by 30% to 60%.
According to the Energy Saving Trust, installing cavity wall insulation can save you between £120 and £350 per year on your heating bills, depending on your property size and fuel type. A detached house heated by mains gas can save up to £350 annually, while a flat might save around £120. If you heat your home with electricity, oil, or LPG, your financial savings will be even higher due to the higher cost per kWh of those fuels.
Mineral wool (or glass wool) is the standard, most cost-effective material and is excellent for general insulation. EPS polystyrene beads are a premium option that is more resistant to moisture and ideal for properties in exposed or damp-prone areas. Polyurethane (PU) foam is the highest performance option, offering the best thermal efficiency and structural rigidity, but it is also the most expensive and can be harder to remove if necessary.
Your property is likely suitable if it was built between the 1920s and 1990s, has an unfilled cavity of at least 50mm, and is in good general repair. Properties built before the 1920s usually have solid walls and cannot have cavity insulation. If your property is in a highly exposed area prone to driving rain, a surveyor may recommend EPS beads or suggest that cavity insulation is not suitable to prevent moisture crossing the cavity.
The installation process is surprisingly quick and usually takes between 2 to 4 hours for an average-sized home. The installers will drill small holes in the mortar joints, blow the insulation material into the cavity using specialized equipment, and then seal the holes with matching mortar. The process is minimally disruptive, and you can use your heating system immediately afterward.
Yes, depending on your circumstances. Under the UK government’s ECO4 (Energy Company Obligation) scheme and the Great British Insulation Scheme, eligible households—such as those on low incomes, receiving certain benefits, or living in properties with poor EPC ratings—may be able to get cavity wall insulation fully funded or heavily subsidized. It is best to check your eligibility with an Ofgem-accredited installer.
Cavity wall insulation is designed to last for the lifetime of the building, typically guaranteed for 25 years by the installer. Many installation companies are registered with CIGA (Cavity Insulation Guarantee Agency), which provides an independent 25-year guarantee that covers the cost of rectifying any issues if the insulation fails or causes problems.
When installed correctly in a suitable property, cavity wall insulation does not cause damp. However, if a property has an existing damp problem, poor pointing, or is in a highly exposed area where rain frequently penetrates the outer brick leaf, the insulation can trap moisture and transfer it to the inner wall. This is why a professional pre-installation survey using a borescope is absolutely essential to check the cavity condition and wall ties.