Resurrecting Cavity wall insulation

[Clive]

Hi,

The post I copied below captures my question and concern about cavity wall insulation exactly.

Does anyone know if systematic, long-term research has been done on the effectiveness and "damp resisting" properties of cavity wall insulation?

I'm guessing if there were significant problems with cavity insulation causing damp bridges the story would have come out in the press years ago.

I too am worried about this being a one way journey but I feel I have to do it because the exterior walls in my terrace are freeeeezing.

patrick j View profile More options 26 Mar 2005, 15:17 Newsgroups: uk.d-i-y From: patrick j Date: Sat, 26 Mar 2005 15:17:20 +0000 Hello

This posting is a bit OT as it concerns something which is not DIY but I do know that there are many here who will be able to answer my questions.

I am contemplating getting cavity wall insulation put in to the walls of my

1954 bungalow.

I'm wondering if there are likely to be any problems with this insulation such as increase in damp?

The reason I ask is because my understanding of cavity walls is that they work because there is a gap, so filling the gap with something seems like a strange thing to do. If something is put in the gap does this not risk transmission of damp from the outer layer of bricks to the inner layer?

I'm also wondering why cavity wall insulation works? After all the transmission of heat through the wall is slowed by the gap, so once again, does putting something in the gap not just give the heat something to transmit through?

As cavity wall insulation has been around for a very long time obviously there are very good reasons for why my fears about it are unfounded, but I ask because putting the insulation in can not be undone, so I would like to be certain it is a good move.

While I'm at it, does the insulation material come in different forms and is there anything to watch out for when I ask someone to do it for me?

Thanks in anticipation.

Happy Easter

-- Patrick

[tony sayer]

In article , Clive scribeth thus

Ours have been done some 14 years now and no damp problems whatever!..

Just do it. Get the right contractor in for the job tho.......

[Andrew Gabriel]

Mine was done when it was built 18 years ago, in the same way it's generally retrofitted nowadays, by drilling holes and blowing in some sort of wool (glass I presume, not sheep;-), except holes were drilled from the inside as it wasn't plastered at that point (they're still visible in unplastered areas, although mortared).

Like Tony says, no problems.

It got a bad name in the early days with fumes leaking out of the early materials, and one or two people finding their kitchens had become encased in polyurathane foam, but I think these are things of the past.

[tony sayer]

In article , Andrew Gabriel scribeth thus

Yes ours was done in the same way and you just don't notice the holes anymore and this was done from the outside at the junctions of the brick where the joints are staggered as it were..

And they did fill the cavities very well too as we've subsequently found out:)..

I should just get on with it whilst you can afford it before the gas bill comes in!....

[Norman Billingham]

There was a lot of discussion about this some 30 or so years ago when it first started to be used. As long as the outer walls are in good condition and the exposure is not extreme there seem to be no problems.

FWIW our previous house was about 200 yards form the sea, facing into SW gales in winter. It was done with the formaldehyde foam in 1977 and has given no problems at all to us or the later occupants - but the brickwork is rendered.

Our present house is a bit further back from the sea abut on an exposed hill-top site. It was done with blown rockwool in 1992 and has given no problems at all - but again, the brickwork is rendered.

In both cases there was a marked reduction in energy bills.

Get lots of quotes - the prices were very variable when ours were done and there are quite a few of the "25% off just this afternoon" type sales deals around.

[Phil L]

it got a bad name in the early days because the materials were readily available and the mixture was mostly water, so for a hundred quid or so, you could set up in buisness, of course all the cowboys fell by the wayside back in the 70's but not until they'd practically destroyed the industry, very few legitimate companies survived, but they did and were first on the scene when the mineral wools came along in the mid eighties.

The fumes you refer to were generated when incorrect mixtures of formaldehyde (one of the components, along with water and polyurethane) reacted with the preservatives on the joist ends. Aside from this, many corners were cut in the early days by odd jobbers, gyppos and everyone else on the bandwagon, and even though PU hasn't been used for 25 years, these horror stories continue to haunt the industry.

To the OP, yes, long term research has been done on CWI, by Knauff insulations, Pilkingtons, and many other global PLC's, both in the lab and 'in the feild' so to speak.

For example there's a 'wet' wall at the factory down the road from me where it's made - a brick built cavity wall, insulated with blown glass wool. On one side of it is a water sprinkler, similar to the kind that does your lawn, and on the other side it's plastered and skimmed...after at least 16 years of continuous 'rain', the skimming is still bone dry, and when was the last time we had 16 years of continuous rain in this country?....although it sometimes feels that way...

And if all this isn't enough, your insulation is backed with a 25 year guarantee which has nothing to do with the company that installs it, it's a seperate agency called CIGA, who oversee many companies (almost all the reputable ones) and make sure everyone adheres to strict guidelines.

[stuart noble]

What the hell are "strict guidelines"? Are they different to optional rules?

[Phil L]

Insulation companies pay into CIGA, who issue the guarantees, and in return, CIGA inspect the work, if it fails, they are thrown out of the scheme and very few people will use that insulation company because it cannot issue it's own guarantee

[Peter Taylor]

All good advice. I was really sceptical about CW insulation when it was first thought of, but in over 40 years of diagnosing building defects, I've only ever seen two problems. Both were a long time ago, caused by dampness ingress through large bubbles that had formed in the formaldehyde foam - probably done by cowboys as you say. But even these were quite easy to cure. It couldn't happen with blown fibres.

Peter

[Andy Champ]

Not all the cowboys. I saw a house on the Isle of Wight once, I cannot date for sure but would think early-mid 90s which had been nearly demolished by foam in the cavity. Large timbers were shoring up the outside of the house, obviously professionally done, and were there to contain the pressure of the foam that had expanded in the cavity and in places produced lumps from the cracks several feet across.

I suppose it *could* have been there for 20 years awaiting the court case, but it seems unlikely.

This of course cannot happen with blown fibre. I've heard that it's problem is settling.

Andy

[Phil L]

I'm afraid you've heard wrong.

It doesn't expand. It was pumped in as a kind of 'froth' not disimilar to froth on a pint of guinness, the only major difference was that when the moisture dried out, it left behind a polyurethane froth, IE millions of bubbles - this foam, when touched, would disintegrate almost on contact - it had no substance to it, - imagine dried beer froth - and I've taken down a few walls that had it in, the first slight breeze would see it disappear over the horizon, it was nothing like the foam that you get these days, that which is used for around windows and frame fixing, which his what it sounds like you are describing - this solvent based stuff has never been used for CWI commercially, although I suppose some numpty must have had a bash at it if he's #got a few thousand cans off ebay for a tenner....

[Phil L]

it doesn't settle, glass fibre that is, or any other blown fibre for that matter, no settlement, not even on a 20 metre high building

[Peter Johnson]

It can be done under the government subsidised scheme as well - just Google cavity wall insullation grants for lots of sites with information.

[Mark]

IME you are only elligible if you are retired or on benefits.

[tony sayer]

In article , Mark scribeth thus

Yes good that isn't it?, and we're supposed to be emitting less CO2 etc..

Think the govvermint could have got this one right;!..

[PeterMcC]

That's for a 100% grant. Most Local Authorities provide grants for non-benefit-qualified applicants and the commercial providers rarely seem to provide insulation without some sort of grant-based deduction from the cost.

B&Q do a 5 bedroom detached house for £198 installed by British Gas.

[Huge]

They do? I knew house prices were falling, but ....

:o)

[Peter Johnson]

(ref government insullation scheme)

It is free for those on benefits or who are retired. It is subsidised for those who aren't. I paid a subsidised £199 to have my loft topped up earlier this year; commercially it would have cost around £500 (four-bed detached house). My understanding is that you can have either the loft or the cavities done under the scheme, not both.

[Steve Firth]

The quickness of the hand deceives the eye. How many rolls at what thickness? What would it have cost to DIY? Did the subsidy do anything other than provide drinking vouchers for person fitting the insulation?

[Mark]

That's my opinion too. I don't call £199 for a loft insulation top up cheap.

The only way I'd install CWI is if I got it free. Otherwise it would take much too long (if ever) to recoup the cost.