Hi,

Had some geezer knock on the door last week regarding cavity wall insulation. To cut a long story short, we are entitled to a free partial cavity wall fill off the back of a government scheme.

I've not asked what material they'll be using etc. but upon reading some articles on the interweb, there appears to be a mixed opinion as to if it's a good idea or not, as it might cause other issues such as damp.

Anyone in the know?

Cheers

--
Q

 

Have you already got some form of insulation ? My house has the thinnest sheet of fibreglass I've ever seen , which means I can't get any other type of cavity fill whether I want it or not

 

Yep I looked at this, and it did seem a potential problem with that woolsack type stuff especially as I had a marginal gap

I used EPS ***** and a cleverly adapted leaf blower to blast them in my cavities

Made a difference too

EPS ***** do not suffer from that potential water transmission problem from one membrane to the other

 

is it a narrow cavity ? -- polypearl is used in these

 

If its a timber framed house forget it!

 

From memory, as I saw the houses being built, the blue blocks already have two sections of foam inside them, then panels of foam were attached to the blocks. The outside wall is normal brick.

So there is a gap of about 3 inches between the outer brick wall and the foam panels attached to the breeze blocks.

Thanks

-
Mike

 

Just had it done at my dads house through the same scheme. They use a bead which doesn't transmit moisture - its part of the FAQ section I think.

The front and back wall are being done so should see some savings for heating the house. Loft insulation is also an option - that's worth its weight in gold.

Beware of the number of test / pilot holes required for filling - one every 1.8m

 

I have some stables attached to the house which have breeze block cavity walls, rendered on the outside or whinstone outer leaf and I have been pondering using beads to insulate/convert them, would save lots of time and money but there is no membrane in the cavity.

Not bothered about losing attached stables as not horsey and the horsey folk I have asked say they wouldn't want stables joined to the house because of smells and vermin.

 

I had mine done about 5 years ago, I wish I'd said no

we get black spots of mould near the downstairs skirting now and at the top of the upstairs windows (we never used to)

I wish there was some way I could get the stupid stuff out

 

This is the stuff they use:

http://www.bbacerts.co.uk/Certificat...1a03062013.pdf

Still in two minds if to cancel or not.

 

it all hinges on whether you believe

"Liquid water penetration — the product will not allow water to cross the wall construction via the insulation (see
section 6)."


when I looked into it all - i was surprised to discover that the first (outer) wall will let moisture thru, and the reason for the gap is to let this water run down the inside of the outer wall

the danger with insulation is that you tend to bridge that gap - thus allowing moisture to hit the second inner wall

 

Yep , thats what a cavity wall is for. My single brick garage gets wet on the inside when it rains (just soakes through the cement joints) so I'd hate to see the state of a nice plastered , painted wall if it made it through.

 

I decided to bin this off, but it was a late decision.
They turned up to do two houses on the street last week and to the workmen’s credit, they refused to start doing the job because the wall construction was something they had not seen before. (something about vents/breathers up and down the full length of the walls) After calling out their gaffer, he looked at the walls and told them it was fine and to carry on. However, the two owners by this point had the gee bee’s about the whole thing, since this unique(?) kind of wall construction hadn’t been picked up the earlier surveys, so they told them not to do it.
I wrote them a letter cancelling, but they still pitched up today to do the work. The workmen were the same ones who had attempted to do the two houses last week and whilst they didn’t say it, I don’t think they had full confidence in what they were doing – but if they refused to do the work, then clearly they would get sacked. They said they get a lot of people who refuse to get it done.
However it just so happens that British Gas were round today to install one of their grumpy old git smart meters, so that I can now bill the kids for leaving lights on. We discussed the loft and cavity walls, and he arranged for somebody to call me back. After a brief discussion about the house, the age and the construction, I was told that A) I was not eligible for the cavity wall fill because the house is not old enough – it was constructed with it built in and b) they wouldn’t do a partial fill of the remaining gap because of the risk of issues in the future, which I can only think is damp/water ingress.
In conclusion I can only assume that the company was set up to milk the government green schemes, and that by the time people might start seeing damp issues, they’ll be long gone with the former directors either living it up in the sun or running another scam.

 

I would have thought it would come through the brick rather than the cement as the bricks should, I think, be more porous.

 

Bricks generally are porous.
You can get non - porous bricks such as engineering bricks, they are generally used for manhole builds or below dpc or dpm.

 

Imo all cavity/warm roof insulation needs an air gap .....

So as not to bridge with the outside material as mentioned above.

 

Yep.
Cavity provides insulation and a means of preventing moisture bridging across into the blockwork, weep holes at the base of the brickwork and above lintels can then disperse the moisture back outside.

 

There's lots of useful information here (and about all the other cack that gets peddled to the ignorant - damp proofing, timber treatment, etc, etc):

http://www.askjeff.co.uk/cavity-wall-fill/