How to fix an attempted insulation retrofit on a '70s cathedral ceiling?
I discovered this website 6 months too late!
After losing heat through a 70's era cathedral ceiling built on 2 x 8 rafters for more years than we liked to count, we decided to replace the roof, sheathing, and insulation in one operation. The area of the hip roof was bid at 2,230 sq. ft., the cathedral ceiling comprising 2,040 sq. ft., leaving a small attic space above bathroom and hallway areas under the peak.
The building contractor proposed a couple of options to gain R-value, but the real challenge was in providing an airtight ceiling – cedar T&G had been applied directly to the bottoms of the rafters when the house was constructed. The boards were butted to the wallboard on the perimeter of the interior walls and trimmed with molding, but no vapor barrier or other attempt at making a contiguous, sealed, ceiling was evident.
We chose to employ two layers of 3" hard foam (foil faced) placed in the bays, giving us an R-38 ceiling. Not as high a value as I would have liked, but better than the R-19 (maybe) we had previously, plus, we couldn't really afford to completely rebuild the entire ceiling and roof structure/facia/gutters to get more. A great amount of 'pink' foam was used to seal the T&G at the perimeter of the wall and ceiling joint, plus each foam block was sealed against the sides of each rafter bay and to each other. The contractor assured us that we would achieve an 'air-tight ceiling'.
The roofing was nicely done on a 4:12 pitch, incorporating continuous ridge venting along the long hip ridges and a short ridge vent on the top ridge over the small attic space. There is also continuous venting around the eaves.There were also three skylights in the cathedral sections. These clearly blocked the airflow in their respective rafter bays, but cross bay vents were planned. The space between the insulation and the underside of the roof sheathing was minimal (and I suspect not consistent).
The house has been more comfortable this winter, but after a recent week of sub freezing weather (but no snow – unusual for Seattle), we had a sudden rise in outside temperature – hi 40's during the day – resulting in multiple drips in the the living spaces, no doubt the result of the melting of frozen condensation on the underside of the sheathing. The contractor is being pretty slow at responding to my request to mitigate the problem and I am at a loss to envision an expedient way to solve this problem.
My question is this: Is there now any way to positively create an air-seal for my existing T&G ceiling? Do I need to remove the existing T&G or can I build it up with a new membrane and new paneling. If that were done, can we ignore the inconsistent air gap?
Posted Mon, 12/16/2013 - 20:56
Edited Tue, 12/17/2013 - 06:16
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