Cavity wall insulation

What is cavity wall insulation?

Cavity wall insulation stops heat from escaping your home by filling your walls with polystyrene, mineral wool or foam. It’s designed for buildings with brick walls that have a gap in between – a feature common in houses built after the 1920s.

How does cavity wall insulation work?

If you have a wall with a cavity, you can ask a professional to install an insulation layer between the walls. They’ll do this by drilling small holes and pumping the material through them, before filling the holes so they can’t be seen.

The process should only take a couple of hours.

Do I need cavity wall insulation?

This depends on whether your walls are solid or not. Properties built in or after 1990s are likely to have insulation already, while those built before will likely need to be insulated.

You can sometimes tell if your walls have a cavity just by looking. Two likely signs are bricks forming regular patterns, or the walls being at least 26cm thick (roughly twice the height of an iPhone 7 screen).

Is cavity wall insulation suited to my property?

Not all properties are suited to cavity wall insulation, even if there is a gap between the building’s walls. Here’s a few pointers:

• The cavity should be at least 50mm wide, and the installer needs to be able to reach all the external walls.
• The brickwork should also be in good condition and not exposed to driving rain – any issues with damp will need to be fixed before installing cavity wall insulation.
• Your house should also not be at risk of flooding.
• Your installer will need to carry out a survey to ensure your house is suitable – this could cost somewhere in the region of £75
  

How much does cavity wall insulation cost?

The cost of cavity wall insulation varies, you can expect to pay about £725 to insulate a detached house, or about £370 for a mid-terrace property.

*Estimates are for a gas-heated home, based on fuel prices as of April 2018 (Energy Saving Trust)

How can I get cavity wall insulation?

If you want cavity wall insulation and your home is suited to it, you should find an installer that’s a member of either:

• The National Insulation Association (NIA)
• The Cavity Insulation Guarantee Agency (CIGA)
• The British Board of Agrément (BBA)

They should follow a code of professional practice, and their installation should come under guarantee by CIGA for 25 years – if not, then the guarantee should be independently backed by an insurer.

What if I’m having issues with cavity wall insulation?

You may experience issues, such as damp or mould, with the cavity wall insulation you have installed in your home. If you do, your first resort should be the company who carried out the installation.

They’ll assess the issue to let you know if the original installation is causing the problem. If so, the installer will either attempt a fix or remove the insulation.

If the installation company aren’t willing to help, or if they’ve gone bust, then you should get in touch with CIGA to see if you have a 25 year CIGA guarantee. If you do, then they’ll attempt to fix the problem according to the terms of the guarantee.

If you aren’t covered by the guarantee, you can still ask CIGA for a form to report bad practice. You should also have a look at any paperwork from the installation job. This could tell you if the work was backed by an independent insurer, which can provide a similar level of cover.

While the wrong type or quality of insulation can cause damp in your home, if your installer or the cover provider shows that the damp was not caused by the installation process, it’s unlikely they’ll carry out or pay for repair works. If you think they’re in the wrong, you should submit a complaint.

Your last port of call should be to contact a company that can carry out the repairs – ideally one that is accredited by NIA, CIGA, or BBA.

Compare energy quotes

Cavity wall insulation is a useful way of keeping the heat in your home and saving on unnecessary energy costs. There are a number of other ways you can reduce your energy bills at home, such as turning off appliances on standby and double-glazing your windows. Learn more with our energy saving tips.

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