Guide to Cavity Wall Insulation
What is cavity wall insulation?
Cavity wall insulation is the insulation material that is installed into the cavity of a building, which is the space between the inner and outer wall. Cavity wall insulation traps the warm air in and prevents air from circulating around the cavity.
How to insulate cavity walls
Cavity walls can be insulated by injecting insulation into the cavity from the outside through drill holes in the outside walls. Insulation is usually mineral wool or polystyrene beads, or polyurethane foam.
How much does cavity wall insulation cost?
The average cost of cavity wall insulation for a detached single story house will be about £400-£450. For a terraced house, you'll be spending around £350-£400. A semi-detached house will cost around £450-£500 for cavity wall insulation. A detached house will be between £700-£750 for blown cavity wall insulation.
How long does cavity wall insulation last?
Cavity wall insulation is designed to last for the entire lifespan of the building. However, expanded foam insulation can shrink over time, and may become less effective over the course of several years.
How to insulate your walls without cavity
To insulate solid walls internally, you can fit insulation boards to the walls. This is otherwise known as dry lining. It involves fixing insulation material to the inner side of a solid external wall, and then covering it with plasterboards or cladding.
How to check cavity wall insulation
If your house was built in the last 20 years or so, the walls are probably already insulated. To find out whether they are, you can do the following: Ask a registered installer for a borescope inspection. The installer will drill a small hole in your external wall to see if your walls are hollow or filled.
To check if it has failed - cold and wet patches on internal walls could be signs of failed CWI. Water-damaged and blistered plaster, wallpaper or painted surfaces are also warning signs. On the external wall, look out for spalled or cracked brickwork.
Can I have my cavity wall insulation removed?
Through the government's Energy Company Obligation (ECO) scheme, it is possible to have the entire removal and installation of cavity walls insulation funded without cost to you. A cavity wall insulation removal grant can save you a lot of money
What is the best cavity wall insulation?
Our best-selling DriTherm Cavity Slab 32 is a water-repellent Glass Mineral Wool slab, designed for use in external full-fill masonry cavity walls, that offers the best thermal performance in the range.
It is non-combustible with the best possible Euroclass A1 reaction to fire classification, and is manufactured using Knauf Insulation's unique bio-based binder, ECOSE Technology.
When was cavity wall insulation introduced?
Cavity wall insulation was first introduced during the 1970s, becoming compulsory in the 1990s for all new UK buildings. Any London property built after 1983 should already have cavity wall insulation fitted, but in older homes it may not be present.
