Cavity wall insulation is an insulation material that provides multi-purpose use and can be applied to the walls, floors, ceilings, and lofts/roofs to improve the building thermal conductivity of a residential or commercial building. Cavity wall insulation is available in a variety of insulation materials and is compressed into durable slabs. The chosen insulation material will depend on the area being insulated and what the insulation is required for. We sell a variety of cavity wall insulation products from top brands.

Showing 1–12 of 125 results

How is cavity wall insulation installed?

Cavity wall insulation can be installed in a variety of methods.
Its can be fitted into joists or rafters in the building, it can be installed into stud walls, or in layered insulation, and masonry partial fill applications. The method used depends on the area being insulated.

How to insulate cavity wall slabs into masonry partial fill cavity walls

When installing cavity wall insulation into a new build or extension, cavity wall slabs are recommended. The slabs should be fitted between the building's outer leaf (breeze blocks) and inner leaf (brickwork) and should be installed as the walls are being built and should start between 100mm and 300mm beneath floor level. It can be held into place using wall ties.
Each board should be secured with a minimum of three wall ties and extra wall ties should be applied around windows and door frames. At all horizontal and vertical joints where slabs are butted together and board edges, suitable tape should be applied. This will provide your building with excellent thermal quality and will last for as long as the building does.

How to insulate cavity wall slabs into a timber frame wall

When installing cavity wall insulation into a wall ensure all timber is installed and all studs and rails are sitting flush with nothing jutting from the wall. Then insert the insulation boards into the frames pushing back the plywood sheathing. If necessary, cut the cavity boards to size to fit firmly into the stud walls. Ensure the wall insulation continues with the floor perimeter.
Use any leftover boards for infill panels and use any cut-offs to fill any gaps in the wall. Foil tape can be applied over any joints or boards butted together to provide extra protection from thermal bridging. Then install a vapor control layer over the warm side of the stud work.
Then apply plasterboard lining over the vapor control layer using suitable plasterboard fastenings.
Building Regulations
The limiting U-value for walls in new dwellings is 0.3 W/m2K
The U-value for buildings other than dwellings is 0.35 W/m2K
Where new thermal elements are constructed, such as in a new extension, they should be at least 0.28 W/m2K

Why use cavity wall insulation?

Cavity wall insulation will prevent heat escaping through the walls. It keeps your property warmer in the winter and cooler in the summer. Different types of cavity wall insulation are available to suit every need such as acoustic advantages, safety measures and thermal efficiency. These components will make your living or working space a more comfortable environment. It also means lower monthly energy bills and making your residential building more energy efficient.
When installing cavity wall insulation remember to take the buildings fixtures and fitting into consideration as it can increase or decrease the wall depth. This can affect factors such as the space in the room. Also take safety measures to ensure insulation is fitted correctly around electrical sockets, wires and ventilation spaces, or the correct procedures are put into place to remove these components.
Always consult a building professional when insulating your walls to prevent the wrong insulation being installed and the possibility of damaging your property. Insulation being applied to existing damage such as mould, wood rot, or damp it can worsen the condition.


Rockwool RWA45 insulation are high-quality resin bonded slabs. They are available in a variety of densities and thicknesses to suit your properties requirements. They provide excellent acoustic, thermal, and fire performance and can be applied to variety of uses such as in walls, ceilings, floors, roofs and so on. They can also be used for soundproofing purposes. They have a thermal conductivity of 0.035 W/mK.


Kingspan Kooltherm K106 Cavity Board is made of premium performance insulation with a fibre-free rigid thermoset phenolic core. It also has a low emissivity composite foil bonded to one side which is the inner facing and should be applies to the inner leaf of the building structure. It has a thermal conductivity of 0.018W/mK and is available in widths from 90mm and 125mm.


Celotex CW4000 is an insulation board specifically designed for partial fill cavity wall applications. CW400 is made from rigid polyisocyanurate and has a low emissivity foil facing bonded to one side. It has a thermal conductivity of 0.022W/mK.

Other cavity wall insulation materials include frametherm slabs and acoustic slabs.