How do I identify whether I have cavity walls?

A registered installer will assess your homes suitability for cavity wall insulation before any insulation work is carried out on your home. Your local Energy Saving Trust advice centre can put you in touch with a registered installer just call 0800 512 012 to be speak to speak to them now.

This is the only way to be sure your home is suitable. But to give you a good idea, here are some questions to ask yourself.

1. Does your home have cavity walls?

Most houses built from 1920 onwards have cavity walls. The easiest way to tell is from the pattern of the bricks on the outside of your house. Please note: houses built in the last ten years or so are likely to have cavity walls that are already insulated.

If your home has cavity walls, the bricks will normally have a regular pattern like this.

If your home has solid walls, the bricks will have an alternating pattern like this.

If the brickwork has been covered, you can also tell a cavity wall by measuring its width. Go to a window or door on one of your external walls, and take a measurement there. If the wall is more than 260mm deep then it probably has a cavity; a much narrower wall suggests that it's solid.

2. Are your cavity walls unfilled?

If you think you have cavity walls and want to check whether they are already filled you can:

• Ask a registered installer. If necessary, they will drill a small hole in your external wall which will show you if your walls are hollow or filled, too. This is called a boroscope inspection, and will sometimes be carried out when an installer comes to assess your homes suitability for cavity wall insulation. Speak to your local Energy Saving Trust advice centre who can put you in touch with an registered installer.
• Check with your local authority's building control department - they might know if your cavity walls have been filled already.

3. Are your external walls easy to access?

Cavity wall insulation is blown into the cavity from the outside of a house. Every part of the wall must be filled with insulation, so it's important that the installer can reach all your external walls.

Also, if your home's external walls join to a house next door, the cavity will be separated at it's dividing line, this involves the installers inserting a cavity barrier to ensure the insulation is contained so that your neighbours aren't affected.

4. What if there is damp?

If you have any damp patches on your internal walls then they should not be insulated until the problem is sorted out. You should speak to a builder who specialises in damp prevention about this.

• All about cavity wall insulation
• How does cavity wall insulation work
• Find out how to get cavity wall insulation installed