Proper insulation is necessary to improve your home’s energy efficiency. Cavity wall insulation is one of the most successful methods used in the UK. But homeowners wonder: Do I already have cavity wall insulation, and how do I check?

This guide will explain the easy ways to identify if cavity wall insulation is installed, how to inspect whether it’s doing a good job, and what you can do if you’re not sure.

What Is Cavity Wall Insulation?

Cavity wall insulation refers to insulating the gap between internal and external layers of a cavity wall using insulating material. Such material, commonly mineral wool, polystyrene beads, or foam, slows heat loss as it holds air within the wall cavity.

In plain words, it is similar to wrapping your home with a blanket, keeping the warmth inside during winter and the heat out during summer. It’s one of the most efficient means of enhancing energy efficiency in existing walls and can drastically reduce energy bills.

How Cavity Walls Work

Before discussing inspection techniques, it is important to understand the typical cavity wall construction.

• A cavity wall is made up of two layers (called “skins” or “leaves”) of blockwork or brick with an intervening gap (the cavity).
  
• The standard cavity wall width is between 50 and 100 mm, varying according to building age and type.
  
• Solid walls, by comparison, have no cavity and are often thicker (the solid walls are usually around 225 mm thick, whereas cavity walls are generally 260 mm or more).

Knowing your wall type is the first step in figuring out whether insulation is present.

Why Cavity Wall Insulation Matters

Installing insulation in cavity walls can:

• Cut heat loss by as much as 35%
• Lower your energy bills by keeping your home warmer during winter and cooler during summer.
• Decreasing carbon emissions and your home becomes more environmentally friendly.
• Keep the draughts out and have a home free from cold spots.

Insulating existing cavity walls is usually recommended as one of the most affordable house energy upgrades.

How to Tell If Cavity Wall Insulation Is Installed

There are several ways to check if cavity wall insulation has been fitted to your home.

1. Look for Small Drill Marks on Your Outside Walls

When cavity wall insulation is added, installers drill small holes—about the size of a coin—into the mortar between the bricks. These holes are later filled, but if you look closely, you may notice slightly different patches in the brickwork. This is one of the most reliable signs of cavity wall insulation in existing walls.

2. Check Your Property Age

• Properties constructed after the mid-1990s tend to have insulation already installed.
  
• Properties constructed between 1920 and 1980 can sometimes have cavity walls but are not likely to be insulated unless they have been retrofitted.
  
• Properties built before 1920 tend to have solid walls rather than cavity walls.

3. Use a Cavity Wall Insulation Certificate Check

If your home had insulation installed professionally under a government-backed scheme, you should have received a cavity wall insulation certificate.

• You can perform a cavity wall insulation guarantee check by contacting the Cavity Insulation Guarantee Agency (CIGA), which covers many UK installations.
  
• This will confirm whether your home has been treated and what insulation material was used.

4. Ask Previous Owners or Builders

If you have just bought your house, inquire with the previous owners or the estate agent, or contact the local recommended cavity wall insulation installers who would have done the work.

5. Professional Survey

The professional survey is the best method. A professional will perform a borescope inspection—a borescope camera fed into the wall—to give a clear picture of whether insulation is present.

How to Tell If a Wall Is Insulated

If you’d like to make a simple check yourself, here are some easy tests:

• Touch test: Put your hand on the inside wall in winter. If it feels quite cold, it may not be insulated.
  
• Thermal imaging camera: Many energy assessors use an infrared camera to detect heat loss. If you hire a surveyor, they can provide this service.
  
• Thickness check: Measure wall thickness at a door or window opening. A thickness over 260mm usually indicates a cavity wall, which may or may not be insulated.

These checks provide valuable clues for identifying good cavity wall insulation without damaging your walls.

Cavity Wall Insulation Advice for Homeowners

If you discover you don’t have insulation, or your insulation may be failing, here are some key points of cavity wall insulation advice:

• Always use recommended cavity wall insulation installers who follow cavity wall insulation best practice.
  
• Poorly installed insulation can cause damp problems, so quality matters.
  
• Make sure the work comes with a guarantee.
  
• Ask your installer what type of insulation is used—options include mineral wool, polystyrene beads, or foam.

How to Check Cavity Wall Insulation Types

There are different types of cavity wall insulation, and each can be checked differently:

• Mineral wool: Fibrous material within the cavity.
  
• Polystyrene beads: Tiny white or grey beads, normally visible during construction.
  
• Foam insulation: Hard set material, normally cream or yellowish in colour.

If unsure, a surveyor can help you identify the type.

What If My Insulation Is Not Working?

Occasionally, insulation gets worn or damp. Signs are:

• Cold patches on your walls that shouldn’t be there
  
• Heating bills that keep going up, even though you already have insulation
  
• Damp spots or mould showing up inside your home

You may need insulation cavity wall repair from the inside or even removal and replacement.

Additional Considerations

• How to construct a cavity wall: As per modern building regs, cavity wall construction needs to meet set insulation standards.
  
• Upgrading existing homes: If your home has old or poorly installed insulation, upgrading with modern materials can improve efficiency.

Loft insulation: Remember that insulating your loft is equally important—most heat escapes through the roof.

FAQ’S