Roof insulation
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Joined: 22 Jul 2021
Posts: 1
Location: Québec, Canada

PostPosted: Sun Aug 15, 2021 10:00 pm    Post subject: Roof insulation Reply with quote

Hi everyone,
I am a new member of the forum, although I did read a lot of post from the last couple of years on different subject.

I am an old house owner (1890 years old) and l truly appreciate everything that is old fashionned, from the material used, the techniques employed and the finish result. I bought this house 3 years ago. For the short story, it is an old presbytary that has been abannonded for 6-7 years in the seventies before it was bought by the previous owner and refurbished in 1990. The house used to be in plaster with hollow walls. The walls have been insulated with fiberglass batts and the attic and roof with blown in fiberglass wool. The house is what we call here a story and a half house, which means that part of the second floor’s ceiling is the roof itself and part of it the attic.

I don’t know if my walls are rotting (hopefully not…) but my house does have a problem of ice barrier in winter/spring. This means that my house suffers from poor ventilation (obvious – the ventilation channel has been insulated….) and/or poor insulation (4-5 inches of blown in fiber glass wool + thermal bridges). My roof is a cedar shingle roof that is 50 % brand new and 50 % 10 years old, and I plan on keeping this roof as long as possible (FYI : the contractor did use new techniques/material when installing the roof, including a pitch based underrofing membrane and cedar breather plus a ridge vent. From what I have heard afterward, these membranes aren’t 100% recommanded in houses like mine but I can’t do anything about it now… The deck was in perfect condition when the now roof was installed).

I am now looking for the best way to deal with my problem. Although my actual ceiling has been covered with gypsum pannels, I would like in some time to remove these and rehabilitate the old plaster ceiling (although I have no idea if it is still in a good enough shape for this).

The only way I see I could tackle this issue without removing the roof is by removing the actual ceiling from the inside, remove the actual insulation and create a ventilation channel and then put back some sort of breathable insulation like rockwool and hope it work. Unfortunately, this would mean removing my plaster wall and reading several post from this forum, this could mean traping humidity in my walls in the future.

I guess that ice barrier were not a problem back then because the hollow roof cavity acted as a vent and even if a lot of heat (I guess) was escaping from there, it was expulsed from the home without causing problems.

What are your thoughts about my problem?

Thank you,

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Joined: 20 Aug 2004
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Location: Portland, Maine, USA

PostPosted: Sun Nov 07, 2021 2:24 pm    Post subject: Reply with quote

I'm not sure what you mean by "ice barrier." Where is the ice forming? Can you provide a photo or illustration of that?

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