Quote:
Originally Posted by Mass_nerder
Hahah, nah. I get enough of that at work!
Didn't mean to start a debate.
I still think it could be an interior air barrier issue, which is why it has emerged during cold weather.
But again, I would consult with a building envelope professional.
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It’s all good, same here. I generally get my construction discussion out on another more construction specific forum.
If Calgary14 has stucco, that could be compounding a problem at the wall assembly but sounds like restoration has been looked at there. Hopefully that doesn’t show again, or elsewhere.
You are right it could be an interior barrier issue. The non-vented soffit is definitely a factor. Adding low level venting inputs in the attic may be the easiest to implement to remove more of the humid air out of the attic before it condenses.
Roof pitches, heal heights and attic insulation value are also factors at play.
In low roof slopes the cold plane of the roof sheathing is close to the insulation layer resulting in minimal air space between the two for the humid air to mix with the dry air and exhaust before it condenses on the sheathing.
Many homes were stupidly built with 3 1/4” truss heals which means on low slopes there may only be roughly R9 over ext walls, and R40-60 in the middle. Studies show you get more heat loss at the exterior edges of ceilings than the middle. Forced air heat may play into this along with heals, and that science thing. Temperature difference between the spaces is often the cause for air movement, so the solution to the problem is to get rid of this winter thing.
I’ve seen crazy things though, like bath fan exhaust pipes laying in attics sending all that humid air straight into the attic. Attic hatches with no weatherstripping or insulation. Attic hatches above showers (my 1910 house has this). Skylight shafts with no insulation around the shaft. Plumbing vent chases, chimney chases, wiring shafts all with wide open gaps into the attic. Electricians clearing insulation to install a light leaving a 4’ circle of no insulation. With air loss goes heat and moisture.