Cavity wall insulation problems

Whether you are considering cavity wall insulation, a new conservatory, new windows or any other change you need to consider whether this is the right thing for your home. Let's be clear about this right from the start - not all houses with a cavity are suitable for cavity wall insulation.

With a proper survey by experienced professionals, installed by reputable contractors using the right system and backed by a warranty, then cavity wall insulation will give you a warmer home, lower fuel bills, an improved energy rating - without any problems at all. The system will last for the life of the house.

There are however occasions when cavity wall insulation is not appropriate – and sometimes we advise people that it is not a suitable system for their home.

We discuss the possible problems with cavity wall insulation below. However, first it is worth addressing a question that some customers have:

“The walls of my house were built with a cavities so is it safe to fill them?”

Having a wall with two layers is an effective way of keeping out damp. The outer layer acts like a sponge and gets wet when it rains, but equally it dries out quickly when it’s not raining. What is important is that dampness cannot be transmitted from the outer wall to the inner wall. So it is not a cavity itself that is important, it is the fact that there are two separate walls without a way for dampness the bridge the cavity.

In fact, if there is evidence that water is penetrating the cavity, for whatever reason, we will recommend that cavity wall insulation is not installed.

In our experience where homes have damp patches and mould it is very often the result of condensation - in other words water moisture created in the home that condenses on cold surfaces and over time leads to the formation of mould. Needless to say if your home has damp patches on the walls it is vital that the cause is understood before installing insulation.

When would problems occur with cavity wall insulation ?

Problems can occur if the property hasn’t been surveyed correctly and insulation is installed in a way that does not comply with the BBA certificate guidelines. For example:

  • The pointing on your walls (the mortar between the bricks) is in poor condition, or there are cracks in the walls.
  • If your home is in an exposed location and we think water may penetrate the cavity.
  • The walls already have forms of insulation inside which is incompatible with the system being proposed.
  • There is rubble in the cavity. Poor building practices may mean that rubble has been left in the cavity. If this is the case then the cavity will need to be cleaned out before it is insulated.
  • There are existing problems in your home caused by penetrating damp. Condensation can easily be confused with penetrating dampness (water coming through the walls).
  • Air bricks are not sleeved. If your home has timber floors it is essential that a good flow of air is maintained underneath the floor. Older houses often have air bricks that are open to the cavity. If this is the case the air bricks must be removed and the surrounding cavity ‘sleeved’ and new air bricks installed to maintain an effective airflow. Any reputable contractor will check air bricks as part of the installation procedure.

In some cases we will recommend that some remedial work is carried out to your home before the cavity walls are insulated, and it is sometimes the case that we will recommend that you do not have the walls insulated at all.

However we should reiterate that it is extremely unlikely that problems with cavity wall insulation will occur when your house has been surveyed correctly and insulation installed by a reputable contractor.

If your the walls of your home have been surveyed correctly then the surveyor will have drilled into the walls in several places and used a boroscope or similar device to look inside the cavity. They should be knowledgeable about the system and able to answer your questions. You might want to ask them:

  • What the depth of your cavity is ?
  • Whether there are any access problems that would hinder the installation team or prevent the cavity from being completely filled ?
  • What the regulations are in relation to ventilation for gas fires and wood burning stoves ?

If you are in doubt that the survey has been done correctly you might want to have a second opinion.

See more about the cavity insulation options available and how we undertake a survey.

If you would like further information about cavity wall insulation please contact us or
request a callback.

Keeping Yorkshire warmer
cold walls, no ventilation cause damp, condensation and mould