Condensation and Cavity Wall Insulation

Often when our surveyors are out surveying people’s homes for Cavity Wall Insulation removal, we are asked about condensation; what causes condensation, how to reduce it and what effect if any it can have on cavity wall insulation. So, we thought the following article might be of some use should you feel you are experiencing condensation problems in your home.


Day-to-day activities such as; cooking, bathing, washing clothes, heating and even breathing produce water vapour. The air can only hold a certain amount of water vapour before it becomes saturated, and condenses back into a liquid. This is what’s known as condensing, the product of which is condensation.


Prolonged exposure to condensation in a property can cause; unsightly staining and damage to décor, mould to grow and in severe cases structural defects.


Types of condensation


Cold bridging – This occurs when moisture heavy air comes into contact with a surface that has a temperature at or below its dew point. This causes the water vapour to condense back into a liquid form and condensation occurs. An example of this could be if rubble or whole bricks are left within cavity after building works or construction, and are touching both sides of the cavity.


Interstitial Condensation


This type of condensation occurs when moisture heavy air disperses within a vapour-permeable material such as cavity wall insulation. If this material is warm on one side (The side nearest your inside walls) and cold on the other side (The side nearest your external wall) the moisture vapour will condense and deposit its liquid state within the material. Wet cavity wall insulation can lead to damp and mould growth if left untreated.

The Problem

Interstitial condensation is perhaps the more insidious, as it is difficult to detect until significant damage has occurred to the building fabric.

Interstitial condensation occurs where warm, moisture-laden air from the interior diffuses into a vapour-permeable material such as fibrous insulation or a porous brick wall. This is most common in cavity walled structures where the cavity is filled with insulation. The air reaches its dew point within the cavity, depositing water in the insulation layer.

The result is the insulation material can become saturated, so it no longer functions as an effective insulation layer. Water droplets can also form within the cavity, leading to damage of structural elements: corrosion of metal wall ties or rotting timber frames. These may not be evident until significant deterioration has occurred.

When the dew point is reached in the outer brick wall, water will be deposited within the porous brick. In very cold weather, the resultant freeze/thaw action can cause spalling or cracking of the brick.

The Solution

One way to prevent the water vapour entering the wall and reaching the cold surface is to apply a vapour proof barrier on the internal wall underneath the plasterboard and decorative finishes. Cavity trays are also required to assist moisture evaporation.


Cavity problems and not sure where to turn?


If you’ve got issues of any other nature with your Cavity Wall Insulation that may be down to the installer not following proper guidelines as to the install. It is now apparent that hundreds of thousands of home owners across the UK will need remedial work that will consist of a full extraction of the Cavity Wall Insulation and could well mean a whole host of other repairs and replacements directly caused by the install.


Contact Wall Cavity Claims today on free phone 0800-8-654321 or visit

1 Comment

  • Veronica Berney

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