Ventilationa and Insulation in Loft Dormer Ceiling

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Hello

I have recently had a loft conversion. As far the dormer is concerned, the ceiling goes like this:

Starting from below:

Spotlights, skim, plasterboard, double c16 joist, xtratherm (foil) insulation on top of the joist, 3 layers of hot bitumen felt, vent all along the dormer beneath the fascia board. There is no bathroom extractor fan flap. I can see the foil insulation well above the vent when I look through my bedroom window.

1) Is this correct?
2) Is it correct to have the felt direct above the insulation (xtratherm) or should there have been a barrier, i.e., board or some sort in between?


My concern is that as the vent is continuous (from left to right of dormer) and there is no insulation touching the plasterboard, when the wind is blowing the air gets through the vent and between the insulation and the ceiling which could cause the ceiling to get very cold hence loosing heat and making the rooms cold.

3) Am I right to assume this?


I see other dormers where there is no open vent, just closed fascia boards, top and below with an extractor fan flap.

4) Why are these different?


Sorry, dont know much about construction....

I am thinking of getting the vent closed.

5) Is this wise to do? I read somewhere that air is needed so as no condensation is caused.


6) Is there anything that can be done so that the rooms dont get cold, that is if the air is causing it... and also stay within the building regulations.

Would appreciate any help. Sorry about so many questions. :)

Thanks
 
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What you have described sounds like a 'warm' roof scenario.

This is where the insulation (+125mm thick) sits wholly above the joists so that the air below, i.e. the ceiling space remaining beneath the insulation and above the plasterboard is at the same temperature as the room underneath.

This ceiling space does not need venting and requires no flow of air through it.
 

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