To ventaliate a roof or not?
I apologize for asking this since it seems like there is more on the web about this topic than one could possibly read. However, you might understand my confusion since there seems to be two schools of thought and each is convinced of their position.
I live in Ontario, Canada, zone 4 if that helps. My home is one hundred years old. It is balloon frame construction with brick veneer. The attic was renovated in the 1960’s but very poorly done. When I replaced the roof five years ago the insulation or lack of was made very apparent.
The soffits are now vented and the roof ridge is vented as well. As it stands the attic appears to have some mold behind the dry wall and no ventilation between soffit and ridge.
It is very hot in the summer and cold in the winter. Ice damming is a problem but not one that has brought water into the house.
My hope is to gut the attic this summer and insulate properly. It will be a bedroom when I am done.
The question is really about spray foam insulation directly against the roof boards. When the roof was changed they had to lay 1/2 inch plywood over the 1 inch pine boards in order to secure the 30 year shingles (in our climate that usually means 15 years!) Spray foam seems to be the best choice with old structures since the space between the rafters changes from section to section and within individual sections. The advice I have found is literally split down the middle. Half say you must vent behind insulation in order to keep your shingles intact and the other half say that heat transfer is prevented by sufficient spray foam so it is not a problem.
Help! My wife thinks I am all over this one but in reality I am confused about the whole project.
Thanks for any help you might be able to offer. Cheers
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