Condensation in loft. 11 December 2022 at 5:03PM in In my home (includes DIY) MoneySaving 87 replies 6.4K views

superstylin

I think I'll just use pipe lagging, there's no chance I'm paying £4 a piece for a bit of plastic. 

housebuyer143

All my condensation has turned to solid ice today 😱 at least I know the heat isn't escaping from the house into the loft 🤣

badatDIY

Fitted the lap vents today - I am guessing the felt is very old as some of it was quite brittle and split around the fixings. So be careful and gentle when you are putting it on! I feel like an extra tear probably helps ventilation more than anything though...

10 was almost enough for my tiny loft space, but might buy a few more if the problem still occurs. I have also pushed down the insulation by the eaves so there is an air gap (quite a lot of it was blocking the airflow!) so hopefully those two things combined will get the ventilation going adequately. I'm also gonna leave my dehumidifier up there for a few hours on constant see if I can get the humidity down below 50 (was 81 when I started it!!!)

Oh yeah one final word of warning - anyone else with the real "smart" idea to use a window vacuum on the felt to get rid of the water... Don't. I only bought mine this week and I fear I have already ruined it with bits of black (which I am assuming is plastic rather than mould, but you never know...). Next time paper towels, for sure.

badatDIY

Doesn't seem to have made any difference. Should I see it clearing up immediately or can it take a few days?

ashe

I don't think it would make an immediate difference as that condensation is already there, I'd expect it would need to evaporate naturally, which would happen over time meanwhile you should get no new, or less new condensation. 

This all assumes your loft hatch is sealed and insulated, extractors all vented correctly, Dow lights have hoods etc and lap vents installed to give enough airflow based on size of roof 

badatDIY

Does insulation on the loft hatch matter? I've sealed it with foam strips now but haven't got around to insulating it. I was under the impression it's airflow not warmth that's the problem?

ashe

badatDIY said:

Does insulation on the loft hatch matter? I've sealed it with foam strips now but haven't got around to insulating it. I was under the impression it's airflow not warmth that's the problem?

Warm air getting into your loft will help cause the condensation 

for me out ceiling in bedroom is 12c and loft hatch is 7.5c so it's obviously much colder therefore leaching heat; that hotter air then gets into loft and helps the condensation form, so it's a combination of wanting airflow to ventilate but also stop the heat getting there in the first place 

stuart45

It's not heat getting into the roof space that's the problem. It's damp air getting into the roof space and because it's much colder there the moisture condenses on the cold surfaces. 
Before roofs were insulated, condensation was less of a problem. 
When you add insulation to an old house it's important to make sure there is adequate ventilation.

ashe

stuart45 said:

It's not heat getting into the roof space that's the problem. It's damp air getting into the roof space and because it's much colder there the moisture condenses on the cold surfaces. 
Before roofs were insulated, condensation was less of a problem. 
When you add insulation to an old house it's important to make sure there is adequate ventilation.

Surely heat loss helps though otherwise we wouldn't need to insulate the ceiling? 

stuart45

You insulate the ceiling to keep the heat in the rooms, and keep your bills down. Having a warm roof space would keep down condensation, but waste money.