According to the Energy Saving Trust (EST), around one-third of the heat loss from most homes is through the walls. By insulating your walls with cavity wall insulation, you can benefit from saving £100’s on your energy bills, help to reduce your carbon footprint and keep your home warm in the winter months.

In this blog, we address some of the frequently asked questions from our customers.

 

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 40mm between. Cavity widths do vary depending on the build type of the property.

Cavities between walls became popular in the 30’s and was a method to control damp and noise. These walls are known in the industry as the outer-leaf and Inner-leaf and tied together using cavity wall ties.

The cavity can help drain any moisture build-up on weather-beaten outer-leaf walls and drain through holes at the bottom of the cavity.

You may ask why solid walls tackle the damp problem? To put it simply, the materials used in solid walls are a lot more porous, making it easier for moisture to move down the wall and drain off.

This is similar to how cavities are now insulated with graphite beads which allow moisture to travel through the cavity and drain off.

 

Is my house suitable?

If your house was built after the 1920s, it is likely to have cavity walls. Older houses (pre-1920) are more likely to have solid walls, with no cavity and possibly no damp proof course.

Before the installation, one of our retrofit surveyors will carry out a free no-obligation assessment of your property to confirm that it is suitable for insulation.

Once it has been confirmed, the survey will be uploaded to the IAA (Installation Assurance Authority) where they will complete an independent inspection to confirm suitability and consumer protection.

Once the property has been independently deemed suitable for retrofit cavity wall insulation, a member of our team will contact you to arrange a date for install.

 

How is cavity wall insulation installed?

Cavity wall insulation is installed by drilling holes through the mortar joint of the outer-leaf. The drill holes are 22-26mm in diameter, depending on the material used. The holes are then made good after injection. Each hole is injected in turn.

I have vents at my property. What will your installers do with these?

Any ventilators supplying air to gas appliances will be safeguarded by installers. This would be the same with any underfloor ventilation or ventilators in to wet room areas. The installers will check to see if these are suitably sleeved.

How long does it take to install wall cavity insulation?

It takes around 1-2 hours to install cavity wall insulation, depending on the size of the property. Cavity wall insulation can also be installed as part of a wider energy efficiency measure, such as during a loft insulation installation.

My house is semi-detached, how do they stop insulation going into my neighbour’s cavity?

The installer will insert a Cavity Insulation Barrier Brush into the cavity wall. The barrier is a flexible brush that is inserted into the hole that has been drilled in the mortar joint from the top of the cavity which is pulled through a hole at the bottom having being tied to a weighted chain that is inserted. The chain is located and pulled through the lower hole and enable the barrier to be appropriately positioned. Once in place, this prevents insulation material from flowing into the neighbouring cavity.

Obviously, if your neighbour has insulated their cavity, a cavity barrier will not be needed.

What about filling the holes?

Yes, the drill holes are pointed after the insulation material has been injected. The installer will use mortar to seal the hole which is matched up as close as possible.

What product do you install?

We install either a bonded bead or white wool fibre products which are both systems of cavity wall insulation that have been tested, assessed, and approved by the British Board of Agreement (BBA) and KIWA.

You can read more about these insulation products in our guide here

I live in a listed building, can I still have cavity wall insulation?

Yes, you can still have cavity wall insulation installed in a listed building. However, you may need to get permission from your local authority first. Wall cavity insulation can also be installed in conservation areas, all works are undertaken under the CWISC competent persons scheme whom notify building control following any installation on completion.

Does cavity wall insulation cause damp?

No, cavity wall insulation does not cause dampness. In fact, it can help to prevent damp by reducing heat loss and draughts. Cavity wall insulation is also effective at reducing condensation.

I live in a thatched property, can I still have cavity wall insulation?

Yes, you can still have cavity wall insulation installed in a thatched property. However, you will need to get permission from your local authority first. However, it is advised that you get a full survey before committing to insulating the home. If there is debris from the roof, this could cause the insulation to fail.

Can I have cavity insulation with external insulation?

Yes, you can have cavity wall insulation with external insulation. External insulation will provide an additional layer of protection against heat loss. Cavity wall insulation is also effective at reducing draughts.