# Vapour barrier around studs?



## joecaption (Nov 30, 2011)

#1 Need your location added to your profile for questions like this. Just go to quick links to edit.


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## ront02769 (Nov 28, 2008)

Yes, you can. Not the optimum solution bur workable. Ron


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## Gary in WA (Mar 11, 2009)

I agree, as long as the vapor barrier is in the warm 1/3 of the cavity insulation. IMO, add some foam board strips on the stud edges before the sheathing ( if wall shear bracing is existing) before your rainscreen approach to prevent thermal bridging there.

Gary


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## wilyum (Jun 18, 2009)

thanks, its looking like ill take the drywall down and do it right, the cottage is only 20x16. Definitely not fun, zigzagging the VB back and forth between each stud, then crunching it in at the top and bottom plates. Gary, is there a company that just sells the foam strips or are you just cutting rigid foam?


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## ericjones (Mar 21, 2014)

Go ahead, but make sure that the drywall insulation is perfect shape and need not be replaced anytime soon! I had a similar situation where in I thought the drywall did not need a replacement but I soon found it to be worn out. And I had to call up the 1800 Drywall people in Toronto asap!


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## Gary in WA (Mar 11, 2009)

"The drywall is in great shape and don't want to replace it."------------- if you want to leave the drywall and not add a vapor barrier at all, just add enough foamboard sheathing on the studs to prevent cavity condensation; http://www.buildingscience.com/docu...ulating-sheathing-vapor-retarder-requirements

It would require adding trim to existing windows/doors, though. I believe your code calls for FB and a rainscreen approach, check with local AHJ.

Gary
PS. Welcome to the forums, Eric J!


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## wilyum (Jun 18, 2009)

Could i not just add kraft faced batts from the outside, as long as the paper was facing the drywall, like u would to insulate the joists in an unvented crawlspace? Or how about 3.5" rigid foam sealed at the edges with spray foam, like u do when u insulate a rim joist? would either of these work without a vapour barrier?


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## wilyum (Jun 18, 2009)

anyone?


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## ront02769 (Nov 28, 2008)

Neither of those would work withOUT a vapor barrier....because both of them ARE vapor barriers, the rigid foam itself and the kraft paper on the fiberglass. For me everything depends on what you want to accomplish. If you just want to tighten things up a bit without touching inside, I'd probably use polyurethane rigid foam closed cell. Comes in widths that slide into a standard stud bay, can get up to r-28 at 3 1/2 inch thickness and is ok to work with. Wouldn't concern myself with doing anything to the studs themselves unless you want to mess with the trim on all of your windows and doors plus there is very little "vapor" making its way through a stud. So slide the foam into place and use some expanding foam in a can to seal edges if necessary. Ron


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## JustinK (Oct 4, 2009)

Fiberglass insulation should be stapled so is doesn't fall down so it wouldnt work


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## ront02769 (Nov 28, 2008)

Not really, it will friction fit and stay right where it is supposed. Just buy the right product, called something like "speed batts" or "fast batts". Ron


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## wilyum (Jun 18, 2009)

So sounds like both options will work, im going to guess the foam would be superior insulator and would last longer, and in areas with lots of wires put the batts?


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## ront02769 (Nov 28, 2008)

The rigid foam will give you more higher r-value and lower u-value than the fiberglass in the ace that you have to work in. That said, some is better than nothing. Ron


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## Gary in WA (Mar 11, 2009)

wilyum said:


> Could i not just add kraft faced batts from the outside, as long as the paper was facing the drywall, like u would to insulate the joists in an unvented crawlspace? Or how about 3.5" rigid foam sealed at the edges with spray foam, like u do when u insulate a rim joist? would either of these work without a vapour barrier?



Your location requires a Class 1 (poly) vapor barrier, though the local AHJ may possibly accept rigid foamboard only (I doubt it), check with them. The asphalt paper-faced fg is only a Class 2;http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers


http://www.buildingscience.com/documents/insights/bsi-073-macbeth-does-vapor-barriers Also requires a ventilated cladding= rainscreen.

Gary


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## wilyum (Jun 18, 2009)

Gary in WA said:


> Your location requires a Class 1 (poly) vapor barrier, though the local AHJ may possibly accept rigid foamboard only (I doubt it), check with them. The asphalt paper-faced fg is only a Class 2;http://www.buildingscience.com/documents/digests/bsd-106-understanding-vapor-barriers
> 
> 
> http://www.buildingscience.com/documents/insights/bsi-073-macbeth-does-vapor-barriers Also requires a ventilated cladding= rainscreen.
> ...


Im going to guess thats why they dont sell it in this province, not up to code.


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