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Cavity wall insulation

Cavity wall insulation FAQs

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Cavity wall insulation FAQs

Our experts answer your most common cavity-wall insulation questions. Read on to find out what you need to know about cavity-wall insulation.

Installing wall insulation is a big decision, so make sure you do your research before you decide. Here we answer popular questions on cavity-wall insulation to help you make the best decision for your home. 

How much will it cost to get wall insulation installed?

The cost of insulating your property’s walls depends on the size of your home, whether the walls are cavity or solid and the condition they’re in.

You’ll find a guide to the approximate costs and savings involved in installing the different types of wall insulation in our guides to cavity wall insulation costs and savings and solid wall insulation

Installing wall insulation is one of the most cost-effective improvements you can make to your home. The savings you make on your heating bills means insulation could pay for itself in as little as nine months.

Make sure that you’re not paying over the odds to heat your home. Use our independent energy switching service, Which? Switch, to look for a cheap energy deal.

Can I get financial help to pay for cavity wall insulation?

Maybe. Under the Energy Company Obligation, some households might be eligible for discounted or free insulation. The eligibility criteria is complex, though. Call the Energy Saving Advice Service on 0300 123 1234 to see if you could be eligible.

How do I know which type of walls my property has?

The picture above shows the difference between cavity walls and solid walls. The pattern of the bricks can often be an indication of the type of wall you might have. 

If your home was built from 1920 onwards, it’s likely to have cavity walls. The cavity should be at least 50mm wide and the walls need to be in good condition to be suitable for cavity wall insulation. 

If your house was built in the past 10 years, it’s likely that the cavity walls have already been insulated.

As wall cavities catch rain coming through the outer wall, could wall insulation become damp?

Provided the insulation material is installed correctly and is water-repellent, damp shouldn’t be an issue.

Any installer registered with the Cavity Insulation Guarantee Agency (CIGA) should check whether your home is suitable. Their work and materials will be covered by a 25-year guarantee.

However, some cavity walls are not suitable for cavity-wall insulation, including those regularly exposed to wind-driven rain.

In early 2011 Which? uncovered some bad practices when it came to getting advice about cavity-wall insulation for a house prone to damp problems. You can read our advice about damp risks and watch our undercover insulation video

Do I need planning permission for wall insulation?

Planning permission is not normally required for wall insulation.

However, if your property is listed, is in a conservation area or the insulation will change the appearance of your property, you should consult your local planning authority.

How do I find a wall insulation installer?

For cavity-wall insulation, choose an installer registered with one of the following organisations:

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

Check that your installer has signed up to a code of professional practice, such as that offered by the NIA. Also ask if the insulation installation is guaranteed for 25 years by the Cavity Insulation Guarantee Agency (CIGA).

The CIGA provides independent 25-year guarantees for cavity wall insulation fitted by registered installers in the UK and Channel Islands.

Visit Which? Trusted Traders to find local, trustworthy installers – go to insulation installers.

You can also contact the Energy Saving Trust (EST) for a list of recommended insulation installers by calling 0300 123 1234.

What other types of insulation could help me save money on my heating bills?

You could save up to £225 a year by insulating your loft

You can buy jackets to fit around your hot water cylinder and piping. These are available from DIY stores and can be fitted yourself, provided that your pipes are easily accessible. The energy savings are much smaller than with wall or loft insulation but, as jackets cost between £5 and £15, they pay for themselves in a year or less.

It’s worth fitting draught excluders to doors, windows and letterboxes to reduce heat loss. Gaps between skirting boards and floorboards are also worth tackling. Remember to close your curtains at dusk to stop heat escaping. 

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Double glazing also cuts heat loss and reduces noise and condensation problems. You can expect savings of up to £110 a year on bills if you replace whole-house single glazing with double glazing. Make sure you use a company you can trust – we reveal the best and worst double glazing companies

To cut your fuel bills further, make sure you're on the right energy tariff. Using our independent not-for-profit switching site, Which? Switch, to compare gas and electricity prices