frost in attic at joint with outside wall | |
hi,
i've got a house with no eaves extending from the side walls. i was up in the attic the other day to inspect the insulation. there seems to be adequate ventilation both thru a vent in the roof, and a number of vents in the gable ends.
i've got about an r16 up there right now which is totally inadequate for edmonton alberta. i'm looking at blowing in cellulose. no need for insulation dams at the eaves as there is no ventilation coming thru there anyway. but that seems to be a problem. it was quite cold outside (-25 c) when i was up there, and i could see a line of frost all along the edge of the roof line where the rafters join up with the outside wall of the house. obviously in 1953 when they built the house, installing some sort of vapour/air barrier was not standard practice. the wood of the rafters at that point is somewhat discolored, so this has been a problem for awhile.
my question is what to do about it. i can't retrofit a vapour barrier on the inside of the house. should i put some poly in each of the spaces between the rafters and out 12"-18" ? could i use a styrofoam board the same way? what about spray foam? i sure could use some advise on this one. thanks- mitch
Answers:
From: Matt Noles
definitely the problem had been there for quite a while due to the discoloration of the wood. depending on the size of the spaces, you could use a combination of poly and spray foam to seal it out.
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