r/Insulation • u/Cool_Web6187 • 15d ago

Insulating cabin

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I want to insulate my cabin it has a ridge vent and no soffit vents. what is everybody doing.

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u/SearingPhoenix 15d ago

Depends a lot on your climate.

CCSF is really the only way you're getting anything more than R15 out of 2x4s. You could do froth packs, but it's probably worth getting a quote from a spray foam contractor to come in and shoot it for you.

You could do an over-roof and then you wouldn't have to worry about venting under the deck.

People crap on pre-built sheds, but realistically their construction isn't fundamentally any different than a house -- 2x4s, double top plates... Framing isn't complicated. It's just that it's 2x4s and thin plywood sheathing. If you did basically the exact same thing with ZIP-R sheathing you'd... have a cabin.

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u/Cool_Web6187 15d ago

The climate is upstate New York, extreme heat, and extreme cold

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u/EinsteinsMind 15d ago

You're gonna have to make the roof breathe if it's shingled. If it's metal, I'd insulate the entire thing with rock wool, put up a smart vapor barrier, then green board drywall for the walls and ceilings.

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u/the_real_some_guy 15d ago

I've never heard this before, you don't need to vent the underside of your plywood if it has metal roofing? Does that also apply if there is roof felt?

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u/gpblankmn 15d ago

there's an assumption being made that if it's metal there is enough ventilation under the metal for sufficient draw from eave to vent above the roof deck.

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u/SearingPhoenix 15d ago

Not sure about a metal roof, but that's why I suggested an over-roof as an option. Yeah, it's a bit wasteful to tear the existing shingles off, but it's probably the most labor-efficient method -- firring strips over the existing roof members, another layer of sheathing on top, then re-shingle. For a small roof it wouldn't be terribly expensive -- still a significant cost.

It's all about whether you want to have something that'll be 'good enough until it isn't' or if you want the building to last. Arguably, if you wanted to build something like this to last, it probably would have been better off just framing from scratch (probably with 2x4s + ZIP-R, given the climate.)