Insulating loft / condensation problem

9 Mar 2021
Reaction score
United Kingdom
Hi all

End of terrace built in 1890.

Since topping up my insulation, I have a significant build up of condensation on the breather membrane in my loft that I’m trying to fix through:
- installing lap vents in between every rafter at the lowest point close to the eaves.
- installing a mechanical extractor fan in bathroom ceiling to duct through loft and out of the roof (we haven’t got one at all currently).
- removal of a strange structure/room in the middle of the loft built with fibreboard that looks like it’s been there for decades, clearly preventing adequate cross ventilation.
- installing some sort of vapour barrier before relaying new glass wool insulation (the current stuff is now wet due to condensation dripping) - is this a good idea and what should I use for the vapour barrier? I bought some thermawrap only to discover I will probably blocking out the phone signal in my house if I lay it.

Any advice much appreciated as the loft is dripping and I’m super worried about rot!!

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Pull back the insulation from the eaves on both sides so that air can flow through.

See also

Pull back the insulation from the eaves on both sides so that air can flow through.

See also

I’ve already done that, there is definitely air coming through there as I can see daylight in some parts but in others it’s completely sealed off. I can’t see a way to create an opening. Assume it’s the way it was built?
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Don't know. Post some pics of the eaves please (inside and out)

Soffits can be drilled.

It is also possible to drill gables, if detatched, but slower.

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