Greetings. I'm looking at insulating my bunkie roof. There is no attic and the trusses are made of 2x4's. The roof is shingled. I am interested in preserving space so after insulating I would like to nail pine boards to the 2x4's. I'm just not sure whether I should use a strofoam, say 2 inch thick and whether I need a vapour barrier between the foam and the pine boards.
Your comments would be appreciated.
I guess you wanted an answer before the long weekend, huh? In terms of insulation and energy conservation, some is better than none. Depending on the styrofoam product you want to use, it may act as a vapour barrier on its own. The blue or pink stuff with the ship lapped joints (no products mentioned intentionally) will work. But there is a big caution with this method: without providing ventilation to the underside of the roof deck, you can create problems with moisture buildup, rot and/or mould. If you are very careful with your cuts to ensure they fit very tightly from rafter to rafter with no gaps, then you'll do well. If you're going to attempt this method, it's best to invest in acoustic sealant and goop up every joint before you put up the pine.
So, next option is poly vapour barrier. Cover the whole ceiling area and overlap the joints a minimum of 6" (a whole rafter bay is easier) and use acoustic sealant to seal between the flaps. But of course we've totally ignored the walls, which you shouldn't. The point I'm trying to make is you can't *just* do the ceiling. This is one of those all or nothing deals (in my opinion) otherwise any moisture will simply follow the path of least resistence. If you want more help or suggestions, email me at dave at hendersonbrothers dot ca.
Good luck with it!
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