Cavity Wall Insulation

What Is Cavity Insulation?

Cavity wall insulation is one of the best and affordable ways you can do to improve your home's energy efficiency.

Houses in the UK mostly have either cavity walls or solid walls:


  • Cavity walls are made of two layers with a gap or ‘cavity’ between them. If your home was built after the 1920s, it's likely to have cavity wall

  • Solid walls have no gap, so they can’t be filled with cavity wall insulation. If your home was built before the 1920s, it's likely the external walls are solid walls rather than 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.

Is My Property Suitable For Cavity Wall Insulation?

The first thing to check before applying for a Grant is whether your home has cavity walls. Most properties built of brick from 1924 onwards are likely to have a cavity. If your property was built before 1924, it is likely to have solid walls as shown on the side:

Another way to tell whether your property has a cavity is if the walls are at least 250mm (10″) thick. Properties that are built after 1982 should already have Cavity Wall Insulation, as building regulations changed to ensure it was fitted during construction.

If you think that your property already has Cavity Wall Insulation, it is not worth applying for a Grant as Cavity Wall Insulation cannot be topped up.

Frequently Asked Questions?


If your property has solid walls, rather than cavity walls, you may be able to claim a grant for


External Wall Insulation or Internal Wall Insulation.



Cavity Wall Insulation FAQs


How long does it take to install Cavity Wall Insulation?


An averaged size property will take around two to three hours.


Will I receive a guarantee?


Yes. The Installer will apply for a 25 year guarantee through one of three organisations: CIGA, Kinnell or GDGC.


How can I tell if my walls are already filled with Cavity Wall Insulation?


If you look closely, especially under the windows, you may be able to see where holes have been drilled and filled with cement. The holes are drilled where the mortar forms a T joint.


Can I get Cavity Wall Insulation if I live in a flat?


The Insulation must be installed from the ground floor to the roof. Each property is assessed individually for the grant, so you must have the consent of any neighbours above and below before you make an application.


What if I have damp in my walls?


You will need to have the problem checked and repaired before applying for Cavity Wall Insulation through EnergyLink. A local builder may be able to help you to assess this.


Are there any health risks from Cavity Wall Insulation?


No. The Insulation is sealed within the walls. If glass fibre is used, this is derived from sand which fits in with the natural brick and mortar fabric of the property.


Where can I find more information?


Visit the CIGA website to find out more about Cavity Wall Insulation: www.ciga.co.uk.