Hi all, speaking to an elderly neighbour this morning, she is having some fellows come round today to insulate the cavity walls in her house. The house is a 2002 build, breeze block with a rough texture concrete render. I can think of a few potential issues here:

1: They will cause a mess drilling into the walls, at the very least she will have to have the house repainted or re-rendered

2: The foam or whatever it is they pump into the cavity will break the air gap, allowing damp to penetrate the inside skin

3: She has one westerly-facing wall which is often exposed to driving rain (this is Wales!) – maybe water will penetrate the render and blow it if the insulation guys don’t seal the holes properly.

Just trying to look out for her really, she’s quite vulnerable and alarm bells are ringing, especially as apparently this is being done for free.

Am I right to be concerned?

Its a fairly common insulation upgrade, additional EPS bead insulation pumped in to the cavitys, it is normally done where the cavity is totally uninsulated though and the value of topping up existing unsulation is questionable.

If it is being done for free it will most likely need a Building Control certificate and if the building control surveyor is genuine then he should make sure its all done correctly

Rain penetration isnt such a big issue on a plastered house and the holes they make are small and easily pointed in.

If you are concerned call your local authority Building Control and ask them if they have an application for the works and ask their opinion.

RJ surely a 2002 build will already have cavity wall insulation?

The points you raise are valid. Even a tiny amount of moisture getting between render and blockwork in the winter during freezing conditions could cause the render to spall. I would definately get it checked out before work begins.

^ second what lyrikal says.

I’d be more concerned that a property built in 2002 needed ‘extra’ insulation. Regs haven’t ‘improved’ that much since then.

Assuming that there is already insulation in there then what is being added needs to compliment it. If there’s already mineral wool in the cavity I can see problems trying to fill it.

I’d be more concerned that a property built in 2002 needed ‘extra’ insulation. Regs haven’t ‘improved’ that much since then.

Yes, yes they have.

Feel free to let her know that a man off a cycling forum is paying about £4500 to have the cavity insulation removed from his house due to the damp problems it is causing. Rendered brick on the rainy west coast of Scotland if the details matter. Ours is wool fibre or whatever it’s called, and was done for free on a council/govt scheme (before we bought the house), and evidently wasn’t done properly. When it’s being done for ‘free’ the company get a nominal sum from the govt, with the temptation to do things quickly and/or shoddily.

(hijack)

greatape, I work in the render trade in Scotland if you need any advice.

Blown wool insulation is a problem, it absorbs or at least wicks moisture. anyone pumping insulation now should be using bonded bead EPS which in theory should not cause any moisture problems.

The easy way to check if a material is suitable for its application is to ask for the British Board of Agrement certificate or look it up yourself online. The certificate will give details of where it should be used and how. Good thing about agrement certificates is that they are factual and free of the advertising nonsence.

Thanks blindmelon. I’ve got a decent local builder on board who’s going to redo some of the render. Just giving the cavity a month or so to dry out first. But if I get stuck I will come your way.

No problem, I’m more a technical specification person than an applicator. Email in profile if you have any questions or anything.

Yes, yes they have.

No they haven’t.

Assuming new build. 0.35 in 2002 – 0.30 in 2012.
Works to existing dwellings are more stringent at 0.28.