Dormer Window cheek insulation advice.

[crispy_wafer]

Hi All,

 

Trying to get me head around the detail for insulating dormer window cheeks.  Construction build up is (from out to in) OSB then a 5*2 frame.  I'll be using kooltherm boards, Should I treat this like other roof detail and leave a gap between the insulation and the OSB board, or should I fit the insulation tight up to the board seal it in and tape over, I'll be insulating the inside too.

 

Many thanks.

Marek

[riboid]

If your insulation is 4" thick, then I would run it flush at the front of your frame and leave a gap at the back (and your drywall or gyproc will be pressing against the frame and insulation), but ensure that your insulation has a good vapour barrier and it is well taped up and always, always, rub your tape down by mechanical means (plastic strip or something) and not just your hands.  Lots of debate and this subject and can get quiet complex.

[Gordo]

I’d avoid any gap as you risk thermal bypass to unconditioned voids. If you have gaps best seal to avoid thermal bypass.