Insulation, Vapour barrier question
One gable on my great room has 7/16 OSB, 5/8 drywall, then painted. This gable is in the area that is heated by infloor radiant. On the other side of this gable is a 2 x 6 wall framed for a second floor granny suite. Right now the granny suite is unfinished and not heated. I had this wall insulated with fibreglass and then vapour barrier (on the granny suite side). Last winter, the vapour barrier had condensation on the insulation side. I am thinking I should take out the fibreglass and put solid foam panels up against the OSB, seal the cracks with spray foam, then put the fibreglass back along with the vapour barrier.
Will I experience any problems now and what about in the future when the granny suite is finished and heated .
I will be doing the ceiling in the granny suite during the winter….the forced air heat ducts are run on the ceiling trusses so want to spray foam the space above the ceiling so that I get good insulation around the ducts. When I do the ceiling, should I put vapour barrier then the drywall or leave out the vapour barrier knowing that it will be sprayed.
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I'm just sayin'
Your vaulted ceiling in the great room shares the wall w/ grandma's place? You put the VB on grandma's side? Not sure I'm reading it right. If so, I think you put VB on the wrong side (cold side). FYI ... the OSB should act as a VB (it's perm rating will meet energy codes for max perm rating ... I think ... plywood typically does).
If you foam something and it is done right ... I think it is the VB ... no need to add ... but let someone else comment, too here. Most foams have good perm rating I think.
I wouldn't necessarily insulate grandmas wall ... at least for energy reasons (maybe sound, though). If it is 'not heated', usually it will be 55+ in there (not good to let the space get to cold). Heat loss is small, then.