What is the cost of External Wall Insulation?

Uninsulated homes can have a heat loss rate of up to 35%. The u-value (measurement of heat loss – the lower the number, the better) of a typical 220mm solid brick wall is between 1.9 to 2.2W/m²K. Applying 90mm of the EWI Pro expanded polystyrene solution (EPS), with mechanical fixings, reinforcing basecoat, and a Silicone render, brings down the u-value of the wall to around 0.27W/m²K. Therefore, insulating walls with External Wall Insulation (EWI) dramatically reduces heat loss from the property. 

The starting price for External Wall Insulation is approximately £100 / m² + VAT for installing a standard 90mm-thick layer of EPS insulation and silicone rendered finish. This will bring the walls of your home in line with a brand-new home built today in terms of energy efficiency. Therefore you could expect to see reductions in your heating bill. 

So, with prices starting at £100/ m², how much does an average house cost to insulate with External Wall Insulation?  

For a mid-terrace property, you should budget around £7,000-15,000 + VAT, although VAT is only charged at 5% for this type of insulation. For a semi-detached property, you are looking at the cost of between £11,000 – £14,000. For a detached property, the price is typically between £18,000 – £22,000. 

Thicker insulation or alternative insulation types such as mineral wool (Rockwool) will increase the price per m², as different mechanical fixings would need to be used, and the materials are more expensive than regular EPS.