How do I stop a leak from my attic?
I'm getting water dripping down the inside walls of two opposite exterior walls. I checked the attic and found 1) frost of the underside of the roofing plywood
2) insulation stuffed to the soffit and touching the roofing plywood
3) 6-ish inches of paper covered fiberglass bats
4) no vapour barrier but the topside of the ceiling has a silver face
5) a 3 inch duct ( crushed but no holes) from the bathroom on top of the insulation leading out to soffit ,
6) some electrical wiring penetrating the ceiling and routed over the insulation
7) several areas of frost that have not leaked water. I had removed snow from the roof a week earlier, and didnt see much ice.. certainly not ridges or buildup.
The occupants use a humidifier three times a week in one of the bedrooms that are leaking. The other area, which is a bedroom and closet corner does not experience humidification.
My thinking is .. not ice damming. Continue to remove blocking from attic edges, seal house-to-attic penetrations like the bathroom vent, and wiring, insulate the bathroom vent.
Any thoughts?
Frost buildup in an attic is a result of moisture that can’t escape, and that is caused by the insulation blocking the soffit vents. I hate to bring you bad news but I think you need to strip it all out and re-insulate. That would afford you the opportunity to install an air barrier and vapor barrier properly at the same time. It’s not necessarily an easy job, but once you remove the existing batts you could lay down a 6 mil poly vapor barrier, seal any penetrations then insulate on top. The problem with the insulation batts blocking the soffits is easily solved with venting, then you could blow in a bed of cellulose insulation. That's the short story, but everyting you need to know is on this page here -
How to insulate attics properly
As for the dryer duct, that is some very moist air so be very sure that it is actually venting out successfully. As for the humidifier, it would be wise to give the tennants a hygrometer (which measures Relative Humidity) and see what it says. They could be using it because the air is dry, but it could lead to mold so they may not be doing themselves any favours. Keeping humidity down to 35-40 RH is generally pretty comfortable, having it up around 55-60 RH or higher is not good for the house and also starts to cause health concerns for occupants.