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SnowFlakeUsername2 t1_jabfv90 wrote

The vapour barrier is behind the interior wall? If so there is some rule of thumb ratio that I can't really remember about adding insulation on the warm side of a vapour barrier. Guessing 1/3rd r value of the insulation on the cold side.(look it up) IMO you don't want anything touching the warm side of the plastic that would trap condensation and grow mold. An air gab between would be a good thing.

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hoppyending OP t1_jabfzok wrote

Good to know. I was concerned about it being on the wrong side of the vapour barrier.

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woodprefect t1_jace031 wrote

You don't want to use a vapour barrier at all if you will hang drywall. The moisture will move through the drywall but not the plastic and now you have mold conditions.

Keep the vapour in or out or allow it to pass all the way through.

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>Incorrect use of vapor barriers is leading to an increase in moisture related problems. Vapor barriers were originally intended to prevent assemblies from getting wet. However, they often prevent assemblies from drying. Vapor barriers installed on the interior of assemblies prevent assemblies from drying inward. This can be a problem in any air-conditioned enclosure. This can be a problem in any below grade space. This can be a problem when there is also a vapor barrier on the exterior. This can be a problem where brick is installed over building paper and vapor permeable sheathing.

https://buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers

If you _have_ to use it for code use certain tweed's which allows the interior to dry.

https://www.certainteed.com/insulation/vapor-barriers/

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CrispyBacon_87 t1_jack1am wrote

This is so ass backwards.... You're contradicting the building codes of countries around the world.

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Thrawn89 t1_jacss96 wrote

You must always follow local code. They require vapor barrier on the interior side of the wall above grade. Also your links just say incorrect use will cause problems, they don't say don't use vapor barriers at all.

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UncleBobPhotography t1_jabkaae wrote

Makes me wonder, what is the warm side in OPs case when there is such a big temperature difference between summer and winter? I guess the inside is the warm side since the delta is larger during the winter than in summer?

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SnowFlakeUsername2 t1_jabnm5h wrote

Could have the terminology wrong. Where I live we typically call the interior the warm side. I'd also guess it is about temperature differential. The condensation problem is much worse going from humid 20c into dry -30c.... plus the moisture on the cold side isn't warm enough to dry the insulation and foundation. So vapour barrier goes on the inside with it's most important job being to keep warm interior air from condensing into a cold wall. In the summer, any moisture inside a wall can dry out and escape out the non-barriered wall.

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UncleBobPhotography t1_jabozqs wrote

I think you've got the terminology right, we say the exact same thing here in Norway. The difference is just that in Norway, the inside is always the warm side. I'm pretty sure you would do it the other way around in Sinagpore.

Especially if you live in a fairly dry area I guess 30c outside won't make too much of an issue in the summer since it's just 5-10 degrees warmer than the inside which is not much compared to the 50c difference you could get in winter.

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