Cavity Wall Insulation: Materials and Side-effects

I read some recent articles on the newsgroup about cavity wall insulation. It is not hard to buy the argument for it, esp. at a reduced price, as subsidised by energy companies.
However, I tried to do some research and came across a claim that it can cause dampness and also that the mineral-wool product is inferior and actually the cause of damp:
http://www.telegraph.co.uk/property/main.jhtml?xml=/property/2008/04/29/pask129.xml
What do folks think and what is your experience?
Thanks!
Kostas
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Kostas Kavoussanakis wrote:

http://www.telegraph.co.uk/property/main.jhtml?xml=/property/2008/04/29/pask129.xml
Damp is a known issue. If water is running down the cavity, as happens occasionally, with insulation there it will soak into it and be trapped, causing damp. In the unlikely event that this occurs, one can repair where the water is getting in.
There are some wall constructions that should never be cavity filled. These are bridged cavities and uneven cavities, such as ratbond and rough stone.
Polystyrene is usually avoided today because of the probems its caused in the past.
NT
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what problems does polystyrene cause? should i remove it from my house?
flammable? does something nasty to electric wires (what?) what else?
[george]
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George (dicegeorge) wrote:

George,
The use of Polystyrene 'balls' is common in cavity fill even today - but fibre fill is gaining popularity/
If your house cavities have been filled for a while with 'balls' and there are no damp patches at various spots on the internal walls, don't worry, there are no problems.
Is it flammable - yes. But its unlikely to catch fire in a cavity wall!
Does soemthing nasty to electric wires - no. And its not a normal practice to run cables in the cavity.
What else - If its polystyrene balls, then they just go everywhere if you have to cut into the cavity. If it's the old Styrene injected foam, then that did cause problems with fumes - But its unlikely that you'll have that.
Hope this helps?
Tanner-'op
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We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "Tanner-'op"
<of polystyrene>

It leaches out the plasticiser and makes the cabling brittle, perhaps leading to fires, so no, no real problems there, then.
--

Dave

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saying something like:

However the plasticisers cause the polystyrene to shrink away from the cable breaking contact. So not a real problem.
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We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember "dennis@home"

Oh no, not a real problem at all. Right.
--

Dave

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Grimly Curmudgeon wrote:

With sheathed twin-and-earth cable it's not considered to be a problem if the cable remains undisturbed.
--
Andy

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We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Andy Wade

Until somebody goes and disturbs it. That'll work, I'm sure. I mean, nobody every goes and rummages around the loft, do they? I'm thinking about the thousands of houses that have polystyrene loft insulation, not to mention the unknown number of houses where cables do (in spite of tannery smell's assertion) pass through cavity walls filled with polystyrene balls. Then there's the really common technique of dry-lining older houses with battens + polystyrene aeroboard, where the cables are simply led willy-nilly round the back of the new lining, with no thought given to the contact 'tween cable and 'styrene.
After I first heard of this degrading effect, I started paying attention to new and older installations and was quite surprised at the number of places I found instances like those above. Trouble is, you just don't know what's been done over the years and imo, there's a whole pile of house fires waiting to happen.
--

Dave

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oh i should be ok then, in the loft today i found old style rubber cables going to a light socket, they were surrounded by sawdust, which is also very very flammable!
I've found mouse tooth damage to some of the wiring, but no electrocuted mice yet!
Ive been vacuuming the sawdust and polysyrene and foam bit out...
--

[george]



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Grimly Curmudgeon wrote:

Unlikely to happen to with the 'inert' polystyrene balls in cavity fill - as in the original question - even if were in contact with live electric cables dropped down the cavity (which is not normal and bad practice anyway).
And I suppose that even if you covered a cable in the polystyrene balls and left it like that for years (as in some of the early attempts at loft insulation) - then all would be ok (apart from a possible heat build-up from some high current carrying cables). Now if you were covering the cable in expanding styrene foam - then your arguments would at least be bear some weight!
As a matter of interest, could you point me in the direction of the BRE digests that support this argument - or any other document that would for that matter
Ah well!
Tanner-'op
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http://www.telegraph.co.uk/property/main.jhtml?xml=/property/2008/04/29/pask129.xml
We had mineral wool injected into our cavity walls many years ago. There has been no damp but the comfort of the house was immediate.
Damp isn't absorbed by mineral wool but there shouldn't be damp in the cavity.
Mary
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On Monday, May 5, 2008 4:20:10 PM UTC+2, Mary Fisher wrote:

Mary, have you placed mineral wool in a tray of water ? See what happens, all be it slow.
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On Sun, 4 May 2008, Kostas Kavoussanakis wrote:

http://www.telegraph.co.uk/property/main.jhtml?xml=/property/2008/04/29/pask129.xml
Many thanks for all the answers.
Kostas
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On Tue, 13 May 2008 14:14:54 +0100 Kostas Kavoussanakis wrote :

Where in the country are you? The risk is higher in coastal areas and the further west you are.
--
Tony Bryer SDA UK 'Software to build on' http://www.sda.co.uk


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On Sunday, May 4, 2008 2:02:30 PM UTC+2, Kostas Kavoussanakis wrote:

Hi,
You identify an old problem that is not explained properly or not at all by many insulation manufacturers.
Whilst a basic product in itself may be waterproof that does not mean the way it is used to produce an insulation product is.
Take for an example glass - it is both waterproof and vapor-proof, but go back to basic school science. If you stand two pieces of glass in water, with a matchstick between one vertical edge, you will see that the water climbs up between the two panes of glass - the smaller the gap the higher it will climb.
This is called capillary traction. The same happens with glass-wool or mineral-wool.
Another point that most fail to mention is - when you insulate externally , in a cavity or internally is that there is the risk of interstitial condensation.
Believe it or not, most wall constructions are not vapor-proof. In other words moisture can travel through a wall. When that moisture meets a cold surface it condenses - that is called interstitial condensation when it happens within a material - the exact point of condensation is called dew point.
ALL insulation should have a vapor barrier on the warm side of the insulation and that should have taped joints or holes.
INTERNAL insulation.
If you insulate the internal of say a solid wall, it should be covered with a vapor barrier unless the product manufacturer states it is not required as is possible with closed cell products.
If you do not, you will find the internal air passes through the insulation and condenses on the inner face of the external wall. Which in time can result in timber rot.
CAVITY WALL insulation.
The same as above can happen.
Also almost every external wall will have minute cracks etc in it, which will permit rain to penetrate and run down the inner surface of the external wall. Unless a pressure hose e.g. a fire hose is directed square on to a wall, such penetration is not detectable when the contractor inspects the cavity. I do not know of any contractor that hoses the entire wall when inspecting the cavity.
This is likely to progressively saturate any insulation unless it is closed cell.
So be warned.
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On Friday, November 2, 2012 6:20:20 PM UTC, snipped-for-privacy@googlemail.com wrote:

It can happen with unVBed CWI, but seldom does.
NT
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CWI inspectors tend to miss key problems... - Dirty narrow cavity, eg, 15-25 to 35-40mm rather than clear 50mm width - Corroded wall ties, eg, black mortar combined with wind driven rain - Brick returns, eg, at random to brace not just openings but outside walls
Corroded wall ties, narrow cavity, brick snots & brick returns bridging cavity, black hygroscopic mortar are all problems for CWI.
The idea is moisture may get in, but as it got in - so it can get out. This is not true in certain cases, some houses aged roof felt has flopped back against the eaves and dump water down the cavity in addition to normal wind driven moisture ingress. The problem is water loading builds up and saturation can occur.
I recall 2% moisture content of glass wool insulation results in 100% loss of insulation value. Where cold bridging occurs local condensation occurs at those points (typically around windows) which can cause decoration damage.
The CIGA guarantee is worthless because it does NOT cover damage caused by Building Defects and any building which is not to current building regulation standards is considered to be defective, not compared to when it was built. So as usual a piece of toilet paper in most instances except where it can be demonstrated the installer was negligent in assessing suitability whereupon I think they do pay for it to be scraped out of the cavity.
Bonded polystyrene ball insulation may outperform glass wool, never checked.
If cavities are 35mm the benefits are still present, but quite small. Modern cavity wall insulation at build involves thick celotex (far better than glass wool) AND usually maintains an air gap so water penetration can run freely down the outer leaf. A common fault then is the insulation separates away from the inner leaf, or a gap is left which results in convection - essentially turning the insulation's effectiveness into little more than "warehoused insulation board".
If you are redecorating a room, and you can afford to lose 50-70mm off it, frankly I would insulate internally with 50-75mm Celotex. It will far outperform CWI in terms of rapid room warmup (and cooldown, more useful in summer) and give the lowest heating loss.
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This sounds like a good idea for those of us without cavity walls then? Brian
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From the Sofa of Brian Gaff Reply address is active
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On 02/11/2012 22:12, snipped-for-privacy@ntlworld.com wrote:

not true in certain cases, some houses aged roof felt has flopped back against the eaves and dump water down the cavity in addition to normal wind driven moisture ingress. The problem is water loading builds up and saturation can occur.

insulation value. Where cold bridging occurs local condensation occurs at those points (typically around windows) which can cause decoration damage.

Building Defects and any building which is not to current building regulation standards is considered to be defective, not compared to when it was built. So as usual a piece of toilet paper in most instances except where it can be demonstrated the installer was negligent in assessing suitability whereupon I think they do pay for it to be scraped out of the cavity.

cavity wall insulation at build involves thick celotex (far better than glass wool) AND usually maintains an air gap so water penetration can run freely down the outer leaf. A common fault then is the insulation separates away from the inner leaf, or a gap is left which results in convection - essentially turning the insulation's effectiveness into little more than "warehoused insulation board".

frankly I would insulate internally with 50-75mm Celotex. It will far outperform CWI in terms of rapid room warmup (and cooldown, more useful in summer) and give the lowest heating loss.

Something like this?:
http://www.celotex.co.uk/products/celotex-products/celotex-pl4000
I'm thinking of fixing some to the alcoves either side of a chimney breast, as I'm in the process of decorating anyway.
Main problem is the coving - original 19C and too much trouble to remove. So thinking of taking the Celotex to within 30cm or so of the ceiling and creating a shelf.
Rob
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