roof rebuilding due to heat leakage

Old 03-27-02, 08:55 PM
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Unhappy roof rebuilding due to heat leakage

We have a open beam roof style (no attic) and we have a continual problem of the asphalt shingles ice damming in the winter and baking in the summer. I feel that the roof is not constructed properly. Can you explain how a roof like this should be made? e.g. inside layer is Knotty cedar, then plastic vapour barrier, then insulation, then plywood, then tar paper and shingles.
Old 03-28-02, 01:51 AM
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That's the way that it's supposed to be built.
Just must not be enough insulation for your climate.
Maybe the only solution is to add another layer of insulation, but that would bury the beams and require another layer of knotty cedar or other ceiling surface.
Have you consulted an experienced building contractor or architect to see if they have any other suggestions?
Old 03-28-02, 07:50 AM
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Unfortunately thats the way most Vaulted ceilings are constructed. The contractors and designers of years past did not understand the problems with this type of construction. Stuffing even more insulation is NOT the answer. The problem lays in the lack of ventilation not the lack of insulation. Most times you see these roof systems packed full of insulation and as you know that does not stop the Main problem. Alot of these type of roof systems were build using 2 by 6 rafters or 2 by 8 and by the time the insulation is stuffed in there is NO room for ventilation. There must be a 1 1/2 to 2 inch air space provided between the insulation and the underside of the roof decking to provide air flow. Along with the air space its best to have a ridge vent system installed and a continuious soffit vent to provide a 50/50 balance of air flow. Another problem is the way these are designed its very hard to achive the proper R-factor at the ceiling as called out by the building code for your climate. Without fixing this problem your sheathing and other wood members will begin to deteriorate.

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