Finishing out a cold attic space – 2×4 rafters – zone 6 – gambrel roof
We’re working on a remodel of our 1920s dutch collonial house. There’s a lot going on with some new construction building a stairway into our attic and turning it into new, livable space. It’s currently a cold roof and we’re going to insulate and finish it out. The roof rafters are dimensional 2×4. We’re in zone 6 and winter temps can hit -20. Also, we’ve had some big snow loads over the last few years. Ice damming is a problem on many houses in our city.
Here’s my insulation plan. Please weigh in and let me know if this sounds like a reasonable approach.
• The roof rafters on the new construction that will join the existing roof will be 2×8
• I plan to sister 2×8 onto the existing 2×4 rafters of the old construction
• Then between all the rafters (new and existing-sistered), 7″ closed cell spray foam (~ R40-R45)
• I am then debating adding some foamboard on top of the sheathing. I’d like to keep this minimal as the rooflines are somewhat complex
Attached is a front profile showing where the attic space is. I understand we’ll lose a bit of livable space with sistering the rafters but I’d prefer to build this as a hot roof system. Thanks for all your expertise!
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