Posted By haese56 on 03 Oct 2017 10:41 PM
Been in a SIPs panel house in Alaska for 5 years and love it. I have a question regarding the roof penetration for out boiler chimney. The sips roof panel was cut away so there's a 2" offset from the metalbestos pipe which I understand for fire safety. There is a metal flashing cap on the roof side, but this has some venting so that it is NOT air tight. On the inside surface there is nothing, just a 2" gap between the sheetrock, OSB, foam, etc, right up to the vented metal cap around the pipe on the roof side. Since the house is so tight, when we run a bathroom exhaust fan the air has to come from somewhere so a good deal of air is drawn through this stack penetration back into the house. Is this acceptable? Or should I be able to get a flashing plate to seal around the stack on the inside? I'm thinking it would have to be specific to the slope of my roof? Or Is there a fireproof foam that could be used? If this does indeed better seal that penetration, where will the intake air come from to feed the bathroom exhaust fan? I have a honeywell HRV system which I run intermitently, will the bathroom fan draw air through that HRV even when it's not running? I know air has to come from somewhere, and there is such a thing as too tight, It just seems like having this fairly substantial "hole" in my roof is not quite the way things should be. The stack goes a good 8' above the roof so I'm really not concerned about boiler exhaust being drawn back in.
you can use the HRV as a bath exhaust fan if it is ducted to the bathroom,
I would fabricate d a metal trim piece for the flue if one is not available