Hoping to get your advice on this. Every year around wintertime, i've had excess humidity buildup in the attic. Last year, I went up into the attic and found that they never broke the 2x bathroom vents out into the soffit. I attributed the moisture buildup to this and had the builder remedy the problem. This year, I once again have excess moisture buildup in the attic, which frosts up against the sheeting, then melts during a thaw, and ends up wetting the insulation. Last year, I had the builder replace the insulation due to its performance characteristics being altered after becoming wet. This year, I will likely do the same, but the problem is -- the builder is STUMPED. They don't know why this is happening. None of the soffit vents are blocked, I have one of the really good high-rising Venmar vents, and about 600sq ft of attic space.
My own theory is that the dryer and the bathrooms vented into the soffit are causing the problem, primarily because the louvers are pointed back into the soffit. I had my spouse run the dryer while i was in the attic, and the entire thing smelt laundry-fresh when she did so. This leads me to suspect that with the natural roof convection, it's drawing the warm humid dryer air back into the attic.
The roof is a gable roof, on a mid-unit (connected on both sides) townhome, with a north-south exposure. Only the north side aspenite is wet, the south is fine. There are no leaks or penetrations in the roof, this is purely a condensation problem. I checked all of the bathroom vent boxes, and they were all well sealed and tuck taped. I also checked all of the rigid and flex vent lines in the attic, and all appear to be well sealed with no penetrations.
I need a professional opinion about this, since I am listing the home on the market, and do not want to pass on any problems to the purchaser, especially while the builder is willing to correct the problem at no cost outside of the warranty period.
In particular, I'd be curious to know if there's any section in the Ontario Building Code that stipulates blocking off the soffit ventilation within a certain distance of the exhaust vents
Thank you so much for your help.