Cavity Wall Insulation
Why consider cavity wall insulation?
Cavity wall insulation dramatically slows the rate that warm air leaves your house through the walls and cool air enters.
In homes built with cavity walls, space between the inner and outer wall can be either empty or poorly insulated. An empty cavity allows heat to pass straight through the wall — escaping outside in winter and entering the room in summer.
In winter, warm air inside the house moves toward colder external walls. Without insulation in the cavity, that heat is lost quickly to the outside, making those rooms feel cold no matter how much the heating is on. In summer, the process reverses: external heat passes through the walls and warms the room, causing it to overheat.
Rooms with more external walls, such as corners, extensions, or north-facing spaces, are usually affected the most because they have more surface area exposed to outdoor temperatures. Insulating the wall cavity slows this heat transfer down, helping those rooms stay closer to the rest of the house temperature year round rather than swinging between extremes.
How is cavity wall insulation fitted?
Our 1970s home had cavity walls and no insulation, so was an ideal candidate to have cavity wall insulation fitted. The house underwent a suitability assessment, a very thorough examination that included going into the loft to check for insulation up there. It also checked that we had no existing cavity wall insulation that had sunk or degraded.
Before cavity wall insulation could be fitted, we had to have vent fitted in our sitting room as we have an open fireplace there. We had the option of sealing the fireplace instead, but although we don’t use it we wanted to retain the option so chose the vent instead. This was fitted low down in a wall.
Cavity wall insulation comes in several flavours. Ours is a mixture of tiny expanded polystyrene beads and a bonding adhesive that holds everything together and stops the insulation sinking inside the wall. Holes are made all over the wall and the mixture pumped in through that. We were finding the little beads everywhere for weeks. In preparation we had to strip back some ivy that was growing up the front of the house, to make it easy to access the wall.
After pumping in the insulation, the team filled all the tiny holes.
How different does it feel inside?
The difference is astonishing. We had this fitted in the autumn, and felt the benefit all through the winter. We no longer feel the house drain of warm air when the heating goes off. The temperature is much more stable and comfortable. This is particularly noticeable in the rooms with large expanses of external wall.
From our experience we would recommend having your cavity walls filled. We used Evolve Home Energy Solutions based in Monmouth and are happy to recommend them too.