Soon to be starting a loft conversion in my house I have noticed on our Architects drawing that he has specified putting 50mm kingspan between the rafters, rafters being 100mm leaving a 50mm continuous air flow and then 72.5mm under the rafters. I know that this whole project has been over engineered and therefore I am wondering whether I can put the 72.5 in between thus leaving a 30mm continuous ventialtion and the 50mm underneath, does any one know the actual regs in this case as I am not sure.
Air ventilation and kingspan
- Thread starter chirpychippy
- Start date
you must fit the thicker insulation across the rafters as to prevent cold bridging through the timbers.
he would probably prefer you to fit 95mm over and 25mm between but this makes fixing difficult due to the fixings length required.
he would probably prefer you to fit 95mm over and 25mm between but this makes fixing difficult due to the fixings length required.
Thank you once again, the breathable felt is an idea but probably not cost effective, stripping the roof, re felting re battoning re tiling re leading plus the hire of the scaffolds front and back for the sake of losing a 100mm on the slope, thanks once again.
check out the kingspan website it has comprehensive diagrams and installation instructions for various roof conditions.don't think thermal bridging through timber is to much of a problem as if the timber depth allows you can put the entire amount of insulation in the rafters as long as ventilation is maintained between the insulation and felt.
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