Cavity Wall Insulation – worth the risk?
- Thread starter Benny5
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I work in the building trade. I'm well aware, a small number of poorly constructed buildings, react unfavourably to certain insulation. I'm also well aware of the idiosyncrasies of buildings, condensation and their suitability for one insulation method over another.
It still does not justify your ignorant..."cavities are there for a reason" garbage, boyo. Stick to googling and dog impressions.
My wife told me cavities shouldn't be filled when I built our extension with cavity batts. One of her friends told her over coffee and chat that CWI causes damp and mould. I don't always listen to her advice. 25 years ago she warned me about getting a computer, as she thought they carried viruses.
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I work in the building trade. I'm well aware, a small number of poorly constructed buildings, react unfavourably to certain insulation. I'm also well aware of the idiosyncrasies of buildings, condensation and their suitability for one insulation method over another.
It still does not justify your ignorant..."cavities are there for a reason" garbage, boyo. Stick to googling and dog impressions.
You are the ignorant one! Do some research lad..........try and get out from behind your pc screen and get into reality lad.
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Our's was CWI'ed in from memory, the early 90's. It was of the blown in, fibre type - It certainly saved us some on the bills, and made the house warmer. No damp issues, my only concern being that it has maybe settled in the cavities, and so is less effective/could do with topping up.
But, why the need for animal impressions?
But, why the need for animal impressions?
Judging by the amount of companies that extract CWI (20+Manchester alone) news articles and the like it, it is obviously a problem for many, the main cause was that the installers didn't know/care what they were doing, most went out of business within a few years, you can also now get a grant to remove it if it goes tits up
Judging by the amount of companies that extract CWI (20+Manchester alone) news articles and the like it, it is obviously a problem for many, the main cause was that the installers didn't know/care what they were doing, most went out of business within a few years, you can also now get a grant to remove it if it goes tits up
That is the government to blame, rather the installers - The government should put an end to these silly, rush, unsupervised, and wasteful of money schemes, .
Settlement is one of the main problems, creating cold spots around eaves, a friend had hers done on a large exposed gable, spent £000s trying to rectify it, i removed some brick in one of the areas and found the insulation soaked and slumped leaving gaps, all been removed now.
Can't believe you've got damp issues in Manchester Charlie, I've heard it never rains there.Judging by the amount of companies that extract CWI (20+Manchester alone) news articles and the like it, it is obviously a problem for many, the main cause was that the installers didn't know/care what they were doing, most went out of business within a few years, you can also now get a grant to remove it if it goes tits up
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IMHO it depends how the house structure is intended to work. If the house has breathable internal plaster/decoration, and brick walls with soft lime mortar then the consensus seems to be that the wall has to "breathe" to keep damp at bay - i.e. any moisture that gets in to the wall fabric must be allowed to evaporate by design. The science behind this is that warm air containing water vapour will diffuse in to the breathable internal walls, and as the wall gets colder the nearer it gets to the outside, at some point the dew point is reached and condensation forms.
Likewise lime mortar external walls are more porous and hence prone to water penetration from outside than cement mortared walls.
The history of early cavity walls describes the cavity originally being introduced primarily to protect the internal decoration and wooden joist ends etc from rotting due to penetrating damp (rather than being a thermal barrier). Ventilating the cavity helps to evaporate both penetrating damp and condensation caused by water vapour passing through from internally. If the ventilated cavity is designed to work this way, then there should be air bricks in to the cavity only, and IMHO if these are present, I personally would not install CWI because it will inhibit ventilation and evaporation.
However if the house is designed to be "airtight" with gypsum plastered internal walls and cement mortared external brick, then there probably won't be cavity wall ventilation airbricks, in which case I think CWI is totally safe. - modern houses have full-fill cavities without issue.
The danger I see is if a wall is designed with a ventilated cavity, which is designed to evaporate interstitial condensation (caused because the walls are breathable) and also any penetrating damp, CWI will likely move the dew point inwards (because the outer skin will now be colder because it is insulated from the warmth of the house by the CWI) so there is a risk of this condensation occurring inside the insulation close to the very cold outer skin. Once the insulation is wet it has a worse thermal performance than an air gap, and the trapped moisture causes internal damp.
My 2p. Other opinions may vary.
Likewise lime mortar external walls are more porous and hence prone to water penetration from outside than cement mortared walls.
The history of early cavity walls describes the cavity originally being introduced primarily to protect the internal decoration and wooden joist ends etc from rotting due to penetrating damp (rather than being a thermal barrier). Ventilating the cavity helps to evaporate both penetrating damp and condensation caused by water vapour passing through from internally. If the ventilated cavity is designed to work this way, then there should be air bricks in to the cavity only, and IMHO if these are present, I personally would not install CWI because it will inhibit ventilation and evaporation.
However if the house is designed to be "airtight" with gypsum plastered internal walls and cement mortared external brick, then there probably won't be cavity wall ventilation airbricks, in which case I think CWI is totally safe. - modern houses have full-fill cavities without issue.
The danger I see is if a wall is designed with a ventilated cavity, which is designed to evaporate interstitial condensation (caused because the walls are breathable) and also any penetrating damp, CWI will likely move the dew point inwards (because the outer skin will now be colder because it is insulated from the warmth of the house by the CWI) so there is a risk of this condensation occurring inside the insulation close to the very cold outer skin. Once the insulation is wet it has a worse thermal performance than an air gap, and the trapped moisture causes internal damp.
My 2p. Other opinions may vary.
The £9.50 weekend residential course at Pontins was not refundable.
Not a very nice or friendly response is it?It still does not justify your ignorant..."cavities are there for a reason" garbage, boyo. Stick to googling and dog impressions.
Why do you think cavities were there then?
The concept of CWI is sound, and done properly it performs well.
Yes the internet is full of these negative stories (along with the negative people who promote them), and not full of the stories where there are no issues. But digressing from that, the actual problem is commonly the system by which CWI tends to be carried out - grant or subsidised works, poor or no initial survey, subcontractors on price work and daily targets, fly-by-night companies.
Properly surveyed, specified and installed, there are no problems.
The reason for that is surely the vast majority of the work is carried out by these fly by night companies, and a large number of houses with cavities are not suitable for CWI, the house my friend had insulated only had damp problems on the exposed gable, her semi neighbours had no problems due to being protected, and when after i suggested it was the CWI at fault, she kept telling me well next door don't have any problems, now 2 years after it was removed no damp
Another problem with older properties is debris in cavities (even found a pair of old work boots once) variation in cavity width, lack of trays and damp detail around openings, at least with the open cavity air can circulate and help to lessen the damp bridging, also heard stories of surveyors insisting on remedial ties on older houses with CWI due to corrosion caused by the damp insulation?
Maybe there is a good reason the internet is full of these horror stories
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