OSB as wind protection?

[menhir]

Hello!

I have an outbuilding that will be converted into a guest cottage. The exterior walls consist of a timber frame with OSB and exterior wall cladding. Is it possible to insulate the frame and install a vapor barrier, OSB, and gypsum board on the inside, or will it be too airtight with OSB on the outside despite the vapor barrier on the warm side of the wall? Does anyone have practical experience with OSB as a wind barrier and can share their experiences?

 

[klaskarlsson]

Hi!

I have an outbuilding that is to be converted into a guest house. The exterior walls consist of a wooden frame with OSB and wall cladding on the outside. Is it okay to insulate the frame and install a vapor barrier, OSB, and drywall on the inside, or will it be too airtight with OSB on the outside despite the vapor barrier on the warm side of the wall? Does anyone have practical experience with OSB as weather protection and can share their experiences?

There should not be any problems. If you are worried that moisture will not escape, and if the guest house is not always heated, you could use a vapor retarder instead of a barrier on the inside. But OSB is not moisture-blocking so it should work well regardless.

 

[menhir]

That shouldn't be any problem. If you're worried that moisture won't escape, and the guest house isn't always heated, you could use a vapor brake instead of a vapor barrier on the inside.
But OSB is not moisture-proof, so regardless, it should work well.

Thanks for your reply. It sounds like it could work. There are two options without tearing down the existing outer wall; either just filling up with insulation and building the inner part of the wall or making ventilation holes at the top and bottom of the OSB from the inside in each section, creating an air gap, and then filling with insulation. Is the latter just unnecessary work that doesn't significantly reduce the moisture risk? I also asked CharGPT and got the response that OSB is not used as wind protection in Sweden since we have much larger temperature differences/risk of condensation than in countries where OSB as wind protection is common. But AI has been wrong before, so proven experience is more reliable...