Cavity Wall Insulation – A Good Idea Or Not?

In a nutshell no it’s a terrible idea. I will qualify that by saying it is just our opinion and in no way represents the general consensus on insulating cavity walls. I also have to make clear that we are not big fans of retrospective cavity wall insulation and not the insulation that we find in the newer build properties which is sometimes fixed to the inner leaf but it still leaves a substantial air gap.

The reason I am against it is because the cavity (gap) in between the outer and inner walls is there for a very good reason. The gap does not allow moisture from the outside (driving rain) to enter the inner walls of the house. The air gap between the two walls doesn’t allow the bridging of moisture from the outer wall into the inner wall.

Basically it’s one of the water and thermal proofing measures that is inherently built into the structure of a house. Any insulation material which fills that gap has the potential to act as a bridge for moisture to wick across the outer wall to the inner wall leading to damp issues on interior walls.

In short we believe that it’s a total waste of time and money.

What is cavity wall insulation ?

A few years ago the government-backed a scheme to insulate people’s houses which would prevent heat loss and therefore encourage the use of less heating. The theory is that if our homes are better insulated and less heat is lost through the walls, we would consume less electricity and gas. In effect it was amongst the first of the green energy schemes.

It involves the filling of the cavity (the gap) between the exterior and interior walls of a property with an insulating material such as fibre, polystyrene beads or foam insulation.

The general idea is that this filling will help keep the warmth in, the cold out and improve the insulating or thermal value of the walls.

Is it really a waste of money and time?

We are against it because we have seen the disasters first hand on some of the claims we have been involved with. However, in some cases it works perfectly well and does help make people’s homes warmer.

What are the advantages and disadvantages of cavity wall insulation?

Advantages

• Better insulation of walls making the house warmer
• The home loses less heat so you use less gas and electricity to heat your home
• Better for the environment

Disadvantages

• The insulation can act as a bridge from the outer wall to the inner wall allowing the moisture to wick across. This can lead to damp patches on inner walls
• If excess moisture is entering the house it could lead to mould and condensation issues
• Usually the cavity air bricks which are installed to help carry excess moisture out of the property are blocked up and one of the natural moisture management measures has been taken away. This can lead to a build up of excess moisture in the property
• If moisture does enter the cavity and the insulation gets wet it’s almost impossible for it to dry naturally. It can stay wet for a very long time (I have seen this with my own eyes).
• Insulating the cavities can lead to a lack of air movement within the property which can lead to a build up of condensation on inner walls. In short the house cannot breathe.
• Over time, retrospective filled insulation can sink to the bottom of the cavity which means not all of the wall is insulated. This can result in cold spots on the walls.

Summary

We have given you the advantages and the disadvantages of having retrospective cavity wall insulation. It must be said that millions of people have had their cavities insulated without issue however, in our experience the disadvantages outweigh any potential benefits.

The cavities are there for a reason and filling them with mineral wool, polystyrene beads or foam insulation defeats the purpose of them being there in the first place. It’s a big no from us.

If you have a damp house or are having problems with cavity wall insulation, condensation or mould issues please contact Rainbow International on 01274 588011.