Following a roof leak that went undetected for months, we suspect the fibreglass slab insulation in the cavity wall has been saturated for some time.
We've been advised to have it all removed and replaced because of mold spores, although this would involve removing at least part of one skin of the wall.
Is replacing it really necessary or will it dry out on its own and any mold spores not be a problem?
Who advised you to do this?
Given there should be a vapour barrier between your plaster and your insulation I don't see how these spores should enter your house?
Best to suck it and see. Don't rush into instant action. There is nothing for mould to sustain itself on. The air is full of mould spores anyway. The problem may well be self resolving, this possibility is one that's been anticipated.
The fibres are treated with a moisture repellent so should not be as wet as you might think. In practice water runs through it rather than remaining caught in the insulation.
If fitted/fitted correctly.
My concern would be the moisture wicking through an internal wall, and a cycle of decorating and damp control until it dries out. A couple of pilot holes should tell you how wet the internal skin is.
However, its not going to dry very fast and not be much of an insulator is it?
Brian
Can you drill a few holes in the outer skin and blow some air through the cavity to dry the stuff out?
Owain
a) It will eventually dry out - but it might take quite a long time;
b) Mould? Who told you that? Seems like some panicky knee jerk reaction to me. Even IF it goes mouldy (unlikely - rockwool is not known for being nutritious to any lifeforms), how are the spres got to get through the inner wall skin?
We were told this by a building company that specialises in damp and remedial work for insurance companies.
I thought it sounded like someone trying to talk the job up which is why I asked. The consensus seems to be that it's exactly that.
Thanks for all the replies.
There you go - they are talking cobblers trying to drum up work.
Cavity insulation batts are treated with a water repellent to prevent them soaking up water (unlike loft insulation which will become waterlogged, like a wool pullover).
The outer skin of the house should breathe anyway. If you are worried fit some airbicks just above the DPC and some at eaves level.
The paragraph above says it all.
Porous brick/bock walls will breathe and dry out.
The vapour barrier (if any) will be on the inside
Given that the leak went undetected, one can presume no signs of internal wall damp were seen.
No surprise there then.
A 1960's ex-council house behind me had the full scaffold treatment recently with a complete cover over the roof. Nothing hapened for 2 weeks then some guys spent a couple of days removing a few tiles (Marley modern on a 37 degree pitch), did a couple of hours of hammering and banging and that was it.
I have since heard that the felt had been damaged and a cracked tile allowed water to soak into the loft insulation and rot the trusses a bit. Apparently the owner claimed on her insurance when a damp patch appeared in a bedroom ceiling and the Ins. Co. paid out £6,000 (!!!!) to 'repair' it. This work could have been done during a dry spell and taken no more then 2 to 3 days.
She's going to have a shock when her renewal premium is due.
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