Cavity Wall Insulation

Cavity Wall Insulation
Cavity Wall Insulation
Cavity Wall Insulation

Cavity Wall Insulation stores the heat within the inner walls, bouncing it back into the room and holding it for longer. This gives you a more even temperature and gets rid of the draughts that come down from the walls.

  • The cavity is located between the inner and outer brickwork of the property (show picture)
  • The main materials used by NIA installers are Mineral Wool (Glass or Rock Wool) and EPS Bead (Polystyrene bead)
  • Cavity Wall Insulation can lower your heating bills, lower wear and tear on your boiler and reduce global warming and climate change
  • CIGA (Cavity Insulation Guarantee Agency) issue an independent 25 year guarantee covering defects in materials and workmanship.
  • The recommended cavity width is 50mm
  • Cavity Wall Insulation can give you an annual saving of up to  £275. There are a number of grants and schemes available to home owners which can substantially reduce the cost of installing these product.


- Cavity Wall Insulation With Blown Mineral Wool

- Cavity Wall Insulation With E.P.S. Beads



BuildingAnnual savingInstallation costPayback timeCarbon dioxide saving per year
Detached £275 £720 5 Years or fewer 1,100 KG
Semi Detached £160 £475 5 Years or fewer 650 KG
Mid Terrace £105 £370 5 Years or fewer 430 KG
Bungalow £110 £430 5 Years or fewer 450 KG
Flat £90 £330 5 Years or fewer 360 KG



What is a cavity wall?

The external wall of a house is constructed of two masonry (brick or block) walls, with a cavity (gap) of at least 50mm between. Metal ties join the two walls together.

How is cavity wall insulation installed?

The cavity wall is injected with insulating material by drilling holes in the external wall, through the mortar joint. Holes are generally of 22-25mm diameter and are ‘made good’ after injection. Each hole is injected in turn, starting at the bottom.

Is my house suitable?

Before the installation, the installing firm will undertake an assessment of your property to confirm that it is suitable for insulation. This assessment may be undertaken by a surveyor or the Technician before installation.

Do I have to do anything before the installation?

The drilling process does create some vibration – so it would be wise to remove ornaments, particularly on external walls, for their safety and your peace of mind.

The Technician will need access to all walls, so he will need to get inside attached garages, lean-to sheds, conservatories etc. The insulation can only be really effective if all walls are done. If you have a wall right on the boundary, you may like to mention to your neighbour, that the Technician will need to go onto their property.

Are all the systems of insulation the same?

There are several different types of insulation:

  • Bonded bead (white polystyrene beads)
  • Glass wool (Yellow or white in colour)
  • Rock wool (Grey/brown in colour)
  • Urea formaldehyde foam (white foam)

Note: both glass wool and rock wool are known as ‘mineral wool’.

All systems of CWI have been tested, assessed and approved by the British Board of Agrément or the British Standards Institution. All are suitable for their purpose.

Except for Urea Formaldehyde foam, the systems can be used in all parts of the UK.

All systems have a similar insulation value.

How do I know the walls are full?

Each system has a defined pattern of holes, which has been tested to verify that it results in a complete fill. Most systems have an automatic cut out, which actuates when the adjacent wall area is full. There is tolerance in the injection pattern so that the material will flow past the next injection hole.

What about the ventilators that are in the external wall?

Ventilators supplying combustion air to fuel burning appliances must be safeguarded. Similarly ventilators at ground level that ventilate below timber floors must be safeguarded. The Technician will investigate them to check they are already sleeved. If they are not, the Technician will remove them and seal around them to stop them being blocked by the insulation. Other vents, which may be redundant, such a cavity vents or vents that used to supply air to open fires in bedrooms may be closed off. The Technician should discuss these with you. Redundant airbricks may be filled.

Do I apply for the CIGA 25 Year Guarantee?

No, the installer or the agent submits the Guarantee application. The Guarantee is posted to you within days of the application being received at CIGA. - Keep it safe

CIGA is non-profit distributing; its only function, is to stand as guarantor for the promises set out in the Guarantee. It has the resources to meet the promises made in the Guarantee.

All professional approved installing firms are members of CIGA and can apply for a CIGA Guarantee, for properties built with traditional cavity walls. You should insist on a CIGA Guarantee, since nothing else can give you the level of assurance to which you are entitled.

How long will the insulation last?

For the life of the building - the British Board of Agrément say so.

Will my house be warmer?

Yes – if your heating is not controlled by a thermostat. However, if you have a thermostat, it will cut out the heating at the same temperature, so you may not notice the difference in the room with the thermostat. However, you should find that the temperature in other parts of your house improves, for example, the small bedroom on the corner.

With CWI, you should find that the house holds its temperature for longer, therefore the time between heating cycles may be longer. The result should be a more even temperature throughout the house and / or a reduced fuel bill.

If I am concerned after the installation – what should I do?

Talk to the installing firm and tell them of your worries. A contract exists between you and the installer, so they must be given the opportunity to investigate your worries.

They will help you.

Solid Wall Insulation

If you live in a home with solid walls, 45% of your heat is escaping through the walls which is costing you money.

Loft Insulation

As much as a third of the heat you pay for could be escaping through your roof.

Draught Proofing

Draught proofing is one of the most inexpensive and effective energy efficiency measures for the home.