Cathedral Ceilings Retrofit – Zone 5
I have house just north of Boston, in Zone 5. It is a contemporary home built in 1983 with nearly 100% cathedral ceilings. I have an active leak on one of the roof sections, and as such will be replacing the roof very shortly. The roof section is 6/12 pitch 22 feet wide and 28 feet high with two layers of asphalt shingles.
I would like to address some of the shortcomings of the existing roof system which are:
Currently inadequate ventilation, with eave vent but no ridge vent. The rafters on this section are 2 x 10, and I suspect the fiberglass insulation is nearly 10 inch thick allowing very little if any ventilation gap. Consequently, I experience awful ice dams and icycles. This is a post and beam house, and there is poor air sealing between the beams and the various ceiling sections (blueboard with plaster skim coat).
I would like to rectify the ice dam situation and would appreciate some input as to the most cost effective way to do so. At the moment, these are some options based on my limited research:
(1) Remove existing asphalt shingles. Cut portions of plywood sheathing out. Remove fiberglass batts. Apply Icynene foam. Paint ceiling with Vapor retarder and caulk gaps between beams and ceiling.
Pros: Seems to solve my ice dam issue, improves insulation. Does not mess up rakes or fascia.
Cons: I am very nervous about any residual smell after foam application. We have a very smell sensitive family, and I have two kids with immune disorders. It just seems like Murphys law that things can go wrong here even though all the marketing hype tells you foam is safe and doesn’t smell.
(2) Remove existing asphalt shingles. Use Hunter Cool vent panels attached directly over existing sheathing (what thickness)? Fill existing eaves vent with foam to seal. Apply new shingles over hunter panels.
Pros: No foam application so no risk of smell.
Cons: My rakes and fascia would have to be adjusted / added for six inches, which would not match the rest of the house and may look poorly. Not sure about the cost.
(3) Stay with standard roof and simply apply ice and water shield to deal with ice dams when they occur and hope that it works. Live with icycles.
Pros: Cheapest solution. Does not alter rakes and fascia.
Cons: Hope that it works (for twenty years).
(4) Remove shingles over existing sheathing. Roofer is proposing to build cold roof directly over existing sheathing with 3/4 inch strapping and new plywood on top.
Pros: Less expensive than foam and Hunter panels. Results in only an inch and a half of rake and fascia adjustment which can be handled by a drip edge.
Cons: Does nothing to improve insulation. Also I have a concern that I am getting some condensation on the underside the existing sheathing which causes mold. This would not improve this and may make it worse.
What are your thoughts as to the best solution for my situation (I don’t have an unlimited budget)? Do you know of contractors in the Boston area who are experienced in solving this situation effectively?
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