vapour barrier condensation

[rocking23nf]

so at the cabin this weekend, i noticed on the wall that faces the sun, had alot of moisture behind the plastic vapour barrier. We were out for 3 days, and while it improved at night, it never went away.

Should i be concerned about this?  Its all new insulation batts, and plastic vapour barrier in the cabin. Theres no attic as its an A frame, so insulatin is stuffed into the frame of the A.

[Alan Gage]

What's the outside wall like? Is it possible it's rain that's gotten behind the siding and is now trapped?

Alan

[rocking23nf]

at first i thought it was rain, but its not.  its all over the walls that face the sun's direction. The walls are shingles since its an Aframe. I assume something to do with the intense heat the shingles generate.

[Alan Gage]

The water had to come from somewhere and since you have a vapor barrier on the inside it shouldn't have come from there.

http://www.greenhomebuilding.com/pdf/RainScreen.pdf

http://www.buildingscience.com/documents/digests/bsd-108-investigating-and-diagnosing-moisture-problems/?searchterm=wet%20cladding

http://www.buildingscience.com/documents/digests/bsd-105-understanding-drainage-planes/?searchterm=wet%20cladding

Alan

[rocking23nf]

i think your misunderstanding me, im talking about plastic vapour barrier,

My wall is Shingles/Tar paper/Sheathing/r12 insulation/vapour barrier/cedar paneling.

The condensation is between the r12 and vapour barrier.  

[Redoverfarm]

Did you install vent baffles in the wall from the foundation to the ridge between the rafters?  Is the ridge vented?

[Alan Gage]

i think your misunderstanding me, im talking about plastic vapour barrier,

My wall is Shingles/Tar paper/Sheathing/r12 insulation/vapour barrier/cedar paneling.

The condensation is between the r12 and vapour barrier.  

That's what I thought you meant. But the water can't just appear because the sun heated up the wall (though that may be why you see condensation inside your vapor barrier on only that wall), it had to come from someplace, and it's most likely it came from the outside. Unless the framing lumber is still drying out.

Alan

[poppy]

Should i be concerned about this?

You better believe it.  That's a huge problem.

If you can't keep moisture out, then you have to let it out. Others know much more about this than I, so they should be along to help out.

[MountainDon]

Where is this building located? What sort of climate?

[rocking23nf]

northern alberta.

-30s in the winter (but we dont use it)
It was 25C on the days i noticed the moisture and really sunny.

I really dont think this is any type of leak. It seems to be caused by the Sun heating up the shingles.

[MountainDon]

I asked about the climate because in places like the deep South here, where it is very hot and humid and nearly everybody has air conditioning. That makes the cold wall the interior and the moisture drives through the wall from the humid exterior to the cooler and lower humidity interior. If a vapor barrier such as yours is used in that sort of climate situation the moisture condenses in the wall on the vapor barrier. So it seems that your interior wall must be colder than outside.


Re-reading the thread I see this is an A-frame "wall". It seems this is acting more like the roof it is as well. Normal roofs are built with an air circulation space under the roof sheathing with lower and upper vents. I think this may be why this is happening. In any event it is good you noticed before paneling the interior side as that moisture will cause mold. I believe that is almost guaranteed. Mold likes dark moist locations.

Removal of the existing insulation and replacement with spray in foam after everything is dried out could be one solution.

[rocking23nf]

The penaling has started, spray foam is not an option, too much money, and this is all brand new insulation, i dont want to throw it away.

your corrent about the wall being a roof, theres no venting area, and in the summer, its cooler inside then outside during the daylight.

[Redoverfarm]

Did you install vent baffles in the wall from the foundation to the ridge between the rafters?  Is the ridge vented?

That is why I asked previously.  You have no way to get rid of the moisture and condensation.  With the rafter-mates you would be carring that moisture to the ridge and expelling it.  Otherwise it has no place to go. 

[firefox]

Mold is not something you want to take chances with.
You need to fix the problem before continuing on.
It will ruin all your good work!
Bruce