We've recently had an extension on the house and builders discovered we have no cavity insulation in original house. Our gas suppliers Eon has offered us rockwool cavity insulation for £100. I've had a bit of a google and some people have suffered damp and condensation afterwards. I'm in two minds whether to get it filled or not. Anyone got any experience of it – good or bad?

I have the same issue and discovered that if your house was designed without it (ours was), then it can cause problems by bridging the gap between the walls. I've decided not to take that risk, and put up with higher bills…

We're just considering this too. The surveyor bloke that came round was very good and have some decent advice.
I need to replace the wooden gutter at the back to plastic like the front, same wooden profile style and fit an extra air brick. Also mentioned that our cavity was only just worthwhile doing as it was pretty big. 120 year old terrace

Generally, and it seems counter productive, in adding cavity wall insulation to older properties you then have to provide additional background ventilation to reduce the risk of condesation.

It seems odd to spend money making the house warmer to then have to add 'holes' to its envelope.

Any competant installer/surveyor should advise that this is the case!

If its done properly there shouldn't be a problem – problems usually occur if the cavity is not filled properly which can cause cold bridging. Rockwool is one of the better products to put in your walls and will make a significant difference to the warmth of your house in winter and a pleasant reduction in bills. Also ensure you have appropriate loft insulation and pipe lagging.

How old is the house?

Let the house breath and wear an extra clothing layer.

Much cheaper.

There is the polstyrene bead bound with adhesive option. I'm sure that would not enable damp to spread.

I have always been a bit sceptical about the effectiveness of blowing mineral fibre insulation into wall cavities (getting past all the obstructions, filling to the required density etc).

Breaching the dampcourse is an obvious pitfall. Surely proper trained installers know about this and how to deal with the problem.

I would have expected that is would be more likely that condensation would appear on uninsulated walls (and have experienced this on a couple of occasions – north facing walls that never get sun on them).

Condensation occurs as a result of inadequate ventilation and differentials in temperature (like cold uninsulated walls). Ventilation is all about doors and windows, not cavity walls. The exception would be with older properties which rely on ventilaion below suspended wooden floors. The air flow through air bricks needs to be maintained, but then the effectiveness of correctly installed cavity wall insulation would be diminished.

It's a case of making sure the right solution is applied to each building.

So are these newspaper articles written by confused journalists who don't really understand what they are talking about? I know a lot of them love a controversial attention grabbing headline (which often borders on totally misleading). I wonder how many accurately explain the difference between damp and condensation. If they understand what is going on.

Insulating your home is of major importance in reducing the unecessary waste of natural resources and we should all buy into it.

If an energy company is offering to insulate your cavity walls for £100, even with a government subsidy, alarm bells should be ringing as to whether this installer is going to do a proper job!

Had our 1950s detatched house done a few years ago.
We've had no problems and the house felt immediately 'snugger' (seems to hold on to heat better), but ymmv.

Is a low price necessarily something to be wary of? We've just had our loft, pipes and tank done for free, from the electricity company, although no doubt the govt ultimately. We're not old age either.

we've been told out house cannot be done. 1934 Brick stone built semi. Internal wall were too rough and stone ties stop it flowing to where it should. Perhaps there are just easier ones to do for the money.

Jeff Howell says:

http://www.telegraph.co.uk/property/propertyadvice/jeffhowell/7985218/Home-improvements-removing-cavity-wall-insulation.html

I got silver bonded beads

took ages to find an installer prepared to do it as part of one of the schemes and we had to pay extra

however I can't see how damp will get across and there are no problems in my house