Insulating under pitched roof in highly ventilated loft

21 Dec 2006
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United Kingdom
With recent sub-zero temperatures this week I've had water dripping from the underside of my sloped roof down into the loft. Not leaks from tiles/felt, but multiple droplets from underside (ie condensation?).

Loft floor is part boarded and mostly insulated with old fibre-glass style rolled insulation between joists.

I'm considering insulating the space under the roof between the eaves to hopefully insulate the underside and prevent the moisture forming and dripping down? However, loft has two large vented bricks at either end which ventilate lots of cool air in the winter, to the point of cold wind blowing through the loft the last week!

With such large ventilated bricks open to the elements, would insulating the underside of the roof be worthwhile or pointless? Should I instead be concentrating on improving insulation on the floor of the loft. Or indeed, insulate both floor and the underside of roof?

Thanks in advance!!
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If you say it is well-ventilated, then you should be looking for the source of the moisture.

Might be:
Hot water in loft tanks due to pumping-over or other fault
Steam from bathroom due to gaps in plaster or no extractor fan used (or extractor blowing into loft)
Damp air from house due to wet washing left over radiators or condensor drier blowing out steam.
Ill-fitting loft hatch allowing warm damp air from house into loft.
Plumbing leak from tanks or pipe in loft
Damp patches from roof leak
I also have damp running down the inside of my roof between the eves, it is the section directly above the loft hatch, the adjacent sections of the roof are dry.
I investigated this due to damp patches on my bathroom ceiling.
Having read the reply to your posting it sound like condensation from warm air through the loft hatch and cold air from as you have, a well ventilated loft space.
Can anyone confirm my suspicions.
I am also thinkinh of ripping out the old insulation, can i dispose of it at the tip. its the old itchy yellow stuff that comes in rolls

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