condensation

[akpolaris]

I have a shop with 16' walls, T1-11 siding, Tyvec wrap, 2 X 6 framing, R-19 craft backed insulation and 6 mil vapor barrier. I am finding a a lot of condensation on the inside of the Tyvec. The inside of the building is heated with radiant heat kept about 50 - 60 degrees. The walls are sheathed with 7/16" OSB. On the south side wall prior to sheathing the last couple of sheets of OSB I noticed that the insulation was wet at the top. I stripped off the vapor barrier and pulled the fiber glass down to let it dry and look for any possible;e leaks. I did not find any leaks but this condensation does not seem right. Any ideas or other things to look at?

 

[Jess]

You building sounds pretty much like mine, other than I used metal siding. The framing and sheeting won't like moisture so its good that you discovered it now before other problems come up. If there a ceiling installed? Air leak at the top plate where the vapour barrier should be sealed? Snow on the roof? You may have moisture coming off the roofing and onto the top of the framed wall. Metal roofing without something under it will sweat and could be the source of the moisture. Good luck with a quick resolution.

 

[pattenp]

Why did you use kraft faced insulation and a plastic vapor barrier. You should have used unfaced batts. I assume you have the kraft paper facing the heated area then covered by the poly. If you put the kraft paper face to the outside against the Tyvek then that's your problem.

 

[75gmck25]

Based on what I've read on the housing science site, you want the vapor barrier on only one side, and it should be the side that is the most prevalent source of moisture. In your case the kraft paper and poly should be on the heated area side, and the Tyvek wrap will still let moisture out in the other direction.

One exception is that if its a basement wall with concrete covered by dirt, then the concrete is the biggest source of recurring moisture and you want the vapor barrier on the basement exterior wall side.

Bruce

 

[DC73]

Do yourself a favor and post your problem on the Q&A forum at GreenBuildingAdvisor.com.

Sounds like you've created a wall that can't breathe. The thinking behind vapor barriers is changing. Most building scientists now use the term vapor retarder as a true vapor barrier can easily trap moisture if construction details aren't perfect. There are different levels of vapor retarders required for different climates. What works in one climate may be disastrous in another. Alaska is one area where the details must be perfect.

The gurus at GBA can set you straight. Another good source of info is BuildingScience.com.

DC

 

[Highbeam]

Your double vapor barrier was a mistake. But if the poly barrier was perfect and both vb layers were on the inside then I can't see it causing this problem.

 

[akpolaris]

The Kraft face an poly are on the heated side. This is an out of pocket project. I used the Kraft vs unfaced insulation then covered it with the poly since it was not sheathed as promptly as I would have liked.

 

[bullnerd]

I think you need to give some more details?

Stick framed building?
Attic insulated yet?
Eve/ridge vents?
No insulation between the t11 and tyvek?
Just wet at the top or all the way down the wall?

 

[akpolaris]

It is stick framed, balloon framing
Ceiling is insulated with R-30 and 6 mil plastic. Not sheathed yet
Good air circulation in attic with trusses and baffles at eaves and vents installed.
No insulation between the siding and tyvec
Just wet at the top.

I pulled the insulation and plastic away to dry out and reinstalled just the fiberglass the other day to see how that looks.

I think you need to give some more details?

Stick framed building?
Attic insulated yet?
Eve/ridge vents?
No insulation between the t11 and tyvek?
Just wet at the top or all the way down the wall?