Condensation on Cathedral Ceiling
Nine months ago I had a new composition shingle roof installed. When the roofer removed the old roofing, he found there were two layers of comp shingles in place. The slope on the roof is 3/12. The drywall is attached directly to the 2×6 rafters, so no attic space. The underlayment is 30lb felt. The roof faces west. City permit was pulled.
About three months ago I noticed that the ceiling above the skylight was glistening in about a 2×2′ area. The moisture is evenly distributed — no water spots (no plumbing). The moisture appears overnight, every night, and for the most part, dries out during the day. The skylight was installed in 1991, and I have never had any problems with it. Still, I called out a local skylight installer to check the flashing, etc. No problems there. My roofer came out and installed an O’Haven roofing vent in the problem area. No improvement at all.
I live in Southern California less than a mile from the beach, and the humidity is usually around 65-70%. This summer has been hotter and more humid than normal, with humidity rising above 80% several times. The cathedral ceiling is in my master bedroom, and I sleep with the skylight and windows open every night. I never use the tiny shower in the master bath, and condensation never appears on any walls, windows, or mirrors. I use my air conditioner infrequently, and its use doesn’t seem to impact the problem one way or the other. The rest of the ceilings in the house have attic space and no problems.
Do you think that I never experienced this problem with the old roofing because its two layers provided a little extra insulation from the sun? Is this a vapor drive problem? Would you suggest a different underlayment? Other than the new O’Haven roofing vent, there are no other vents on the roof, or venting holes under the eaves. My roofer claims to have never run into this problem in his 20+ years of roofing. He admits to not knowing what to do to solve the problem. He wants to try drilling some ventilation holes under the eaves next. In your opinion, will this help? As for insulation in the rafter area, I assume it is there, but I haven’t checked yet. Please help. My roofer is clearly spinning like a top. All I know for sure is that the problem started with the new roof, and the only thing that really changed, is that I now have one layer of roofing where before I had two.
I recently lost my husband to cancer, and I’m feeling overwhelmed here and in need of some honest advice. Thank you listening. 🙂
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