Cavity Wall Insulation

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 from the bottom.

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 of the technician before 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 the walls, so they 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 your boundary, you may like to mention to your neighbour, that the technician will need to go onto their property.

The technician must undertake checks before and after installation, including any heating appliances, so it is essential that they have access to the property.

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 a bristle brush. Of course, if the neighbour’s house were to be insulated at the same time, the cavity barrier would not be needed.

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 Agrement 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.

All technicians (team leaders) undergo training by the systems 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.

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.

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. They will also monitor the amount of material used for the size of your property to ensure 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.

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 as 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 air-bricks may be filled.

The technician will fill all the injection holes with mortar to match the existing as closely as possible. They will user a mix that closely matches the existing colour and texture. On pebbledash finishes, they will apply pebbles to the surface to match the existing finish. After weathering, the holes are difficult to see.

Normally, the installing firm will not paint the injection holes. Unfortunately, even if the original paint is used, it may not match due to weathering. So it may be necessary for you to consider painting the area, after the mortar has dried. You should discuss and agree what will be done, with the installing firm.

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.

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.

No, not to the cavity wall insulation, but normal building maintenance is needed.

For the life of the building – the British Board of Agreement say so.

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.