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Flat roof dormer very airy and cold in room

dormer cold roof, i have vents above windows into facia , it is freezing in the winter and i can feel draught ,i feel the wall and ceiling which have insualtion in and dormer built 12yrs ago may not be sufficient, kingspan insulation boards where put in full all over in dormer .I am thinking of building a stud wall on exiting dormer walls and putting extra 3inch insulation to the walls and putting battons on exiting flat roof dormer and putting extra 2inch kingsapn inulation ,will this make dormer more warm and keep in heat as the heat just dispates so quickly and makes room feel freezing ,dormer is very airy if it makes sense its like cold is sticking to my arm hair, dormer is 13ft by 13ft and covered in mineral felt ,the dormer is far too big and just not retainig heat well and very airy.Will condensation be a issue?

1 Answer from a MyBuilder Roofer

Best Answer

You need background ventilation, when we convert lofts we have to put 100mm insulation board between the rafters then cross baton and go over it again with 50mm giving 150mm in total. You could always have a warm roof installed on the top, this is where insulation is sandwiched between the roof boards and roofing membrane. You can also get a thermal camera to see where your losing most of the heat just to be sure, also check the size of your radiator and room size to make sure the u value is right for the room, there are calculators online for this.
Hope this helps
Many thanks Aaron (DRS)


Answered 9th Sep 2017

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