cavity wall insulation

clogger

is this a good idea? A firm is offering this service free backed by government grant, however there is evidence on internet forums of damp problems occuring after installation which is then almost impossible to attribute to the firm who install the damp proofing (despite them telling you they are insured against any problems). I would like the savings on the winter bills but as I have no damp problem now am I better to leave well alone?

iamcornholio

clogger wrote: »

however there is evidence on internet forums of damp problems occuring after installation

There is actually no evidence of this.

Inappropriate installation can be an issue, as can the installation highlight or exasperate existing damp or internal condensation problems - but CWI does not cause damp

warmhands.coldheart

clogger wrote: »

is this a good idea? A firm is offering this service free backed by government grant, however there is evidence on internet forums of damp problems occuring after installation which is then almost impossible to attribute to the firm who install the damp proofing (despite them telling you they are insured against any problems). I would like the savings on the winter bills but as I have no damp problem now am I better to leave well alone?

I've heard of damp issues but only when cavities Topped Up with a different material to what was originally used... i.e. Beads pumped in on top of rockwool

27col

If you would rather pay the heating bills in an uninsulated house, than those in an insulated house then you have more money than sense. It's a no-brainer. Even if a small area did develop a damp problem(unlikely). It would be easy to fix because you would know exactly where to open the wall to clear the material bridging the cavity.

jhe

i must be the minority but had mine insulated a few years ago, its a pre war, north facing cold house, i have never felt any difference since the cavity walls were done.

societys_child

iamcornholio wrote: »

There is actually no evidence of this.

Inappropriate installation can be an issue, as can the installation highlight or exasperate existing damp or internal condensation problems - but CWI does not cause damp

Except that, many houses were designed to allow the cavity to breath. That's why they put air bricks in the outer leaf . The air gap was an integral part of the design.

I looked into this a few years ago and found lots of evidence, perhaps that's why there are companies who now specialise in CWI removal.

I had no damp or condensation and still haven't but in damp/wet conditions the bricks forming the outer leaf absorb moisture, which is then released when the sun shines and the temperature rises, causing Efflorescence (white salts and phosphates)

Now I'm so lucky, that at some time in the past, parts of the outer brickwork were painted . . . there was no problem with this before I had CWI installed, but within a short time the paint started falling off some of the bricks, accompanied with the formation of the salts.

Looked an unholy mess . . just spent the past week removing the paint from the affected part of the front of my house . So at that rate I've about 3 or 4 more weeks work!

The only way I've found to do this is using an angle grinder and expensive Poly Discs (and managed to only burn-out one angle grinder - so far)

Did notice the house was much warmer when I had it installed a few years ago so don't really want to remove the insulation, but it does appear to cause many people problems and there's plenty evidence of this on the web.

iamcornholio

societys_child wrote: »

Except that, many houses were designed to allow the cavity to breath.

That is actually an outdated concept/bad design, and a cavity wall is a cavity wall. Insulating it does not cause it to become damp

In any case, would that come under inappropriate installation wouldn't it, where there is a situation where insulation should not be used?

runninglea

It was on watchdog a while ago that some houses pre 1935 or so should have a proper survey done before any insulation is put in.

It was to do with the actual cavity - it also showed several houses where a lot of damage had been caused once the insulation had been put in place.

A lot of companies knock on your door,say you qualify but don't carry out the necessary surveys

societys_child

But you can't do much about "outdated concept/bad design" when the house is already standing (1945)

By effectively blocking the cavity, air cannot circulate and this causes dampness, bit like keeping your bathroom window closed and complaining about condensation. Circulating air helps prevent damp.

As far as inappropriate installation goes, this is the point, many houses were not designed to have the cavity blocked but his wont stop most of the CWI installers when there are subsidies to be had and the "surveyors" are on commission.

So if installing CWI causes damp problems that weren't there before (forgetting whether the building is suitable or not) then the CWI must be causing the damp?

irishcol

iamcornholio wrote: »

There is actually no evidence of this.

Inappropriate installation can be an issue, as can the installation highlight or exasperate existing damp or internal condensation problems - but CWI does not cause damp

It can cause damp on very exposed facades (typically those near the coast or exposed to driving rain). but as you say, the pre-installation survey should identify any such areas and not recommend installation.

clogger

thanks for the replies
The pre installation survey consisted of the man looking at two sides of the semi and declaring yes we can do that, took him three mins tops! The firms involved are payed by the goverment with I think help from some of the utilities so they are real keen to install. At first I said yes (free after all whats the harm) then I thought I had better find out about it as the cavity isnt there for nothing after all, many stories on the internet of problems and despite the company saying if there is a problem we are fully insured, apparantly proving they caused your problem is not easy, so yes I would like a lower winter gas bill but I also like my house and dont want to damage it.