Airsealing a kneewall
NickBrody
| Posted in General Questions on
I have been struggling to find a solution to an insulation issue. I have a cape cod with dormers. The exterior of the kneewall is open bays covered with fiberglass. I wnt to airseal the bays keeping the fiberglass in. The access is tight and I can’t bring in large pieces of foamboard. Any suggestions? Something like Thermawrap seems like a perfect solution but it’s quite expensive and almost impossible to find. A flexible wrap would allow me to wrap the dormers too (also open stud bays).
Zone 5
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Replies
I insulated a similar space with rigid foam board. I brought the pieces in in manageable size panels, then tacked them up with screws and plastic “insulation washers”. I sealed the gaps with some canned foam. It’s tedious, but it works.
If you’re just trying to put up some kind of air barrier behind the batts to limit convection currents and resulting R value reduction, try stapling up some housewrap.
Bill
Housewrap and tape would be the cheap and easy route, but it won't solve all the woes of a cape. I'm in the same boat.
https://www.greenbuildingadvisor.com/article/insulating-a-cape-cod-house
I hate to say it, but spray foam against the roof deck often makes the most sense. If you're lucky enough to be in climate zone 3 or below, go for dense packed cellulose and a vapor diffusion vent at the ridge.
Thanks, folks.
Insulating the roof above the rooms is not in the cards. The house is relatively new and I am not planning to open the roof space. I am closing off the spaces between the floor joist too. I may have to do foamboard.