What is a cavity wall?
The external walls of most houses consist of two masonry (brick or block) walls, with a cavity gap of at least 50mm between them. Metal ties join the two walls together.
How is cavity wall insulation injected?
The cavity wall is injected with insulating material by drilling holes in the external wall through the mortar joints. Holes are generally between 22mm and 25mm in diameter and are 'made good' after injection, so they won't be too noticeable. Each hole is injected in turn, starting at the bottom.
How long does it take?
Cavity wall insulation normally takes around two hours to install, but the exact time depends on the size of the house plus other factors such as access.
Do I have to do anything before installation?
The drilling process creates some vibration, so it would be wise to remove ornaments, especially from external walls. The technician needs access to all walls of the house, so will need to get inside attached garages, lean-to sheds, conservatories, and so on. The installation can only really be effective if every wall is done. If you have a wall right on the boundary with a neighbour, you may like to tell them the technician will need to go on their property.
Is my house suitable?
Before the installation firm undertakes any work, they will undertake an assessment of your property to make sure it's suitable. This will be undertaken by a surveyor or the technician.
Is there much mess?
The drilling process will create a little dust, which will be cleared when the job's completed. It might be wise to remove vehicles from the drive and things close to the walls.
My House is Semi-Detached. How Do They Stop Insulation Going Into My Neighbour's Cavity?
Assuming your neighbour's house is not already insulated, the technician will insert a cavity barrier at the party wall line. This is usually a length of bristle brush. Of course, if your neighbour's house was to be insulated at the same time, the barrier would not be needed.
Does the technician have to come into my home?
The technician must undertake checks before and after installation, including any heating appliances, so it's essential that they have access inside the property. Apart from these checks, all work is carried out from the outside.
Are all systems of insulation the same?
There are several different types of insulation available. We have chosen InstaFibre White Glass Wool, Yellow Glass Wool, Rockwool, and InstaBead because they are all simple to install. Note: Glass Wool and Rockwool are often referred to as 'mineral wool'.
All systems of cavity wall insulation have been tested, assessed, and approved by the British Board of Agrement or the British Standards Insulation. All systems have a similar insulation value. Whichever system you decide on, you can be sure that the installer can offer a 25-year CIGA guarantee.
Are the technicians trained?
All technicians (team leaders) undergo training by the system supplier and the installing firm to ensure they are competent in CWI and carry a training card. Please feel free to ask to see the training card.
How do I know that 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 activates when the adjacent wall area. There is tolerance in the injection pattern so the material will flow past the next injection hole.
Is the insulation dense?
No, as the insulation is contained within a masonry wall, it doesn't need to be 'dense'. For insulation and other purposes, a light density is better. Before installation, the technician will undertake a quality test to ensure the insulation will go into the wall at the right density. He will also note the amount of material used, to know that sufficient insulation has been installed. Note: Drilling a hole in the outer wall and testing the cavity fill with a rod or pencil will not provide any meaningful information.
What about the ventilators that are stored 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 if they are already sleeved. If they are not, the technician will remove them and seal around them to prevent them from being blocked by the insulation. Other vents which may be redundant such as cavity vents or vents used to supply air to open fires in bedrooms might be closed off, and redundant airbricks may be filled. The technician should discuss this with you.
But my house has painted areas!
Normally, the installing firm will not paint the injection holes. Unfortunately, even if the original paint is used it may not match due to wea
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