Identifying cavity wall insulation problems

Poorly installed cavity wall insulation can cause problems. In July 2020 the Chancellor announced a Green Homes Grant to give up to £5,000 in vouchers for insulation (BBC News, July 2020)

A few years ago, we wrote this article about the problems (usually damp) associated with cavity wall insulation. At the time it was thought the issue could be widespread as numerous news articles demonstrated. One newspaper reported: : “1.5 million homes are blighted by damp after cowboy builders cash in on a Government insulation drive”. Another asked: “Could the cavity-wall insulation scandal rival PPI?”.

As funding is now available for homeowners, we wanted to make sure that you didn’t fall foul of the same issues that have occurred in the past.

What is a cavity wall?

Many post war properties (and quite a few pre-war properties) were constructed with external cavity walls. These comprise an outer leaf (usually of brickwork), a gap and an inner leaf (usually of brickwork or concrete blockwork).

The construction reduces the risk of water penetration through the outer walls and enhances a wall’s thermal performance. Each leaf of the wall is connected to the other by a series of cavity wall ties, made of either stainless steel, or mild steel or iron, depending on the age of the house. Older steel or iron ties are susceptible to rusting and failure, so a programme of cavity wall tie replacement is often required, but that is a matter for another posting.

Eventually the building regulations required that cavity walls are insulated, typically with a rigid insulating ‘batt’ within the void. Older walls, usually over 40 years old, often have no insulation at all and the void is open.

Cavity Wall Insulation Problems

Why do properties need cavity wall insulation?

For some years, adding cavity insulation has been recommended as a means of improving a building’s thermal efficiency. A system of government grants, including this most recent one in July 2020, has encouraged householders and contractors to carry out work across the country. However, not all cavity walls are suitable for insulation.

The process seems simple, drill into the outer wall, inject a fibre or bead insulation into the cavity, make good the holes, sit back and enjoy reduced energy bills. The problem is that this fills the cavity with a material that can allow water to cross the cavity causing dampness and if the material is not evenly distributed cold spots where insulation is missing can attract condensation.

When done properly to a building in the right location there is no question that a building’s performance is enhanced. However, done badly or applied to an unsuitable property, a building’s performance can be significantly compromised. Problems of water penetration, condensation, dampness and cavity wall tie deterioration can occur.

Can all houses have cavity wall insulation?

There are many factors to consider when establishing suitability for cavity wall insulation. These include the construction of the wall and site conditions such as exposure to driving rain and the properties location.  This makes sense after all a property on top of a cliff in the north of Scotland will behave very differently to one in the centre of London. Unless a property is fully protected you simply cannot guess the degree of exposure and this needs properly calculating. Other aspects to be assessed include presence of cavity bridges, the width of a cavity, the condition of the brickwork and the presence of services and ventilation.

Walls not suitable for insulation may include:

  • Walls particularly exposed to driving rain
  • Walls with a cavity of less than 40mm
  • Timber frame walls – these often have a brick outer leaf and look like cavity walls
  • Metal framed buildings and walls
  • Walls with lots of cavity bridges
  • Walls in a poor structural condition
  • Walls with a parapet that does not have a cavity tray
  • Walls more than 12m high

This is not an exhaustive list and you should always seek advice if you are unsure.

What problems can cavity wall insulation cause?

We have inspected several properties where expensive cavity wall insulation has led to expensive remedial work. These are buildings where cavity wall insulation should never have been installed in the first place.

Typical problems include the bizarre to the downright dangerous:

  • Attempts to cavity insulate a solid brick wall. This may sound ridiculous but we have witnessed it.
  • Poorly filled cavities resulting in cold spots and internal condensation (the image below shows with infra-red where the insulation in the wall is missing).
  • Blocked bathroom and bedroom ventilation bricks causing condensation.
  • Blocked air bricks forming part of a gas heating ventilation system. This is simply dangerous.
  • Internal dampness caused by the cavity being bridged by insulation and allowing moisture to penetrate from outside through the wall to the inside.
  • Insulation of obviously and excessively exposed walls like cliff top and seaward facing property, something many of my readers from the Kent coast should be aware of.

Are there rules for cavity wall insulation?

The installation of retro fit cavity wall insulation is covered by the Building Regulations and must be carried out and designed by a person in a competent installer scheme. The guidance is based on a withdrawn British Standard BS 8208 ‘Assessment of suitability of external cavity walls for filling with thermal insulants’. This suggests a series of checks that an installer must follow to establish whether a wall is suitable for insulation. This must be done before work starts.

They are common sense logical checks. If they have not been carried out, or not carried out properly then an installer has been negligent in progressing their work. A tick box form is not sufficient as it is usually necessary to actually calculate the exposure a building has.

How do you fix cavity wall insulation problems?

As far as remedial actions are concerned, none are especially straightforward. In some cases, the best course of action is the removal of the insulation. This may require sections of the outer leaf to be removed (and subsequently rebuilt) to facilitate access. In one case we dealt with, the whole outer leaf was taken down and rebuilt. Alternatively, and depending upon other factors, some form of external sealant or cladding may be appropriate. Each case needs to be reviewed on its merits. There may also be internal decorative and remedial work to undertake.

Who pays for remedial work to bad cavity wall insulation?

Well, possibly you.

Many installations are covered by a Cavity Insulation Guarantee Agency (CIGA) guarantee – often sold as being Government-backed. It isn’t. CIGA is an independent provider of guarantees for work undertaken by its registered installers only.

How can I identify cavity wall insulation problems?

If you have internal dampness that you think is due to cavity wall insulation, or if you need to make a claim, you may want or need an independent survey and inspection. Collier Stevens can inspect cavity wall insulations and verify their compliance or otherwise with the relevant Standards and Codes of Practice. This includes the all-important calculation of exposure to wind-driven rain. This is the bit that installers very often trip up on!

And if you are an installer who is dealing with an unjustified claim, well, we have helped defend you too. Not all installations are bad.

If you think we can help you with a dispute, or you would like some advice, please contact us via the form below or give us a call.