Cavity wall insulation causing damp

[Frankiebaby]

Several years ago I was foolish enough to install cavity wall insulation. Since then I have noticed a musty smell inside which is getting worse as time passes. The smell is extra strong if we have been away from home for several days when all doors and windows are closed. We have condensation on the windows which we didn't have before and a length of wall approx. 6' long x 1' high above the skirting is quite damp. Here in the UK it appears that there is a high level of complaints like mine and a lot worse for some. There is a 25-year CIGA guarantee on the job but I am informed that the body who deals with complaints is financed by the UKs insulation installers and apparently they come up with all sorts of excuses to exonerate the installers and try and find causes that is not covered by the guarantee. Removal of the cavity insulation is very costly and I was wondering if installing air bricks around the exterior of the house would help. I believe the insulation installed in my home is not the small polystyrene balls. I think it's some form of fibre. Another thing I have noticed is that the exterior painted render is developing large blisters with quite a lot of moisture behind them. Am I right in thinking that the cavity insulation is allowing moisture to breech the damp-course and the only way out is through the walls?[/b]

 

[JohnD]

It's unlikely

You are mistaken in thinking that there is a high level of problems.

It appears that you have defective walls. Rainwater can penetrate through cracked or gappy pointing, render or pointing. You say you have defective render. Have it hacked off and replaced. Very likely rain is collecting in these bubbles. If you puncture one of them near the bottom after rain, water may drip out.

Are the walls wet on the outside, perhaps due to persistent driving rain or overspilling gutters?

How do you ventilate this house?

How do you dry your washing?

When you raised your concerns with the installer, did they inspect the house? What was their response?

Tape a piece of clear plastic tightly to the wall. After a few days, inspect it and see if water droplets are appearing on it and, if so, where.

 

[freddiemercurystwin]

It should stated though that this kind of post from the OP is not uncommon and that following the installation of cavity wall insulation, problems seem to develop with regards to dampness and condensation where there were none before.

So whilst the OP's walls may well have had problems that may well have been present before the installation of cavity wall insulation, they were not causing a problems per se whereas they are now.

So whilst the problems may not be a result of a faulty installation, the house should maybe not have had CWI installed in the first place.

 

[JohnD]

yes, and so the installer is responsible for surveying the property beforehand and can be forced to remove insulation at own expense if not.

 

[freddiemercurystwin]

Yes I agree entirely, the issue is that the surveyors (well salesmen) do not possess the necessary education in order to assess the suitability of a particular building. So arguably that is included in the installation as a whole. But how often has an installer been forced to accept responsibility? Incredibly rarely I suspect.

 

[Frankiebaby]

Thanks both for the info. The bungalow has a well-maintained painted rendered exterior. The render is in good condition. I always use Dulux Weathershield Masonry paint and I repaint every three years. The crack I referred to in a previous message is a historic one and has always been cleaned out thoroughly and filled prior to painting. This crack used to be dry when hacking out to renew the filler but since cavity wall insulation the crack is damp/wet. Blisters are forming on the smooth-rendered plinth under the upper render which is spar dashed. No blisters have ever formed here until CWI. We dry clothes outside or in a tumble-dryer which has a vent-pipe to the outside. Weather permitting, we open windows in the morning and close them early afternoon. We have gas central heating. I need to renew the filler in the crack and paint it before a representative of CIGA make an inspection because I know they are going to blame the dampness on that. I know for a fact that the crack is not the cause because it was present before CWI and I never had a problem before.

 

[theprinceofdarkness]

As the external skin is growing blisters now. It can not be rain getting in as the outer skin has been getting wet for all its life.
The strip on the inner leaf that is wet, its not under a window is it. I think the real reason is that as the room is getting warmer, the air in it is carrying more water. before all the walls were cold so a layer of condensation was actually forming every where but it was so minute, that it was not detectable. Now most of the walls are warm, so the condensation just appears on the cold bits, the window and the strip along the skirting board, if its under the window , it means that this area has not been filled properly.
The one litre of sweat a human produces every night has to go some where and it ends up on the coolest surface unless vented out. This water is soaking into the wall from the inside and as the ventilation in the cavity is very much lower then it used to be, soaks through the outer skin via a dodgy cavity (debris?).
Frank

 

[Frankiebaby]

Thanks princeofdarkness. Yes, the damp strip is under a window. I may have to ask a builder to knock a hole from the outside into the cavity to do an inspection.