Repairing damage from ice dams (cathedral ceiling and HVAC in attic)
My six year old house has chronic roof problems. The question is not what went wrong, but how to fix it. My pride is set aside and I am open and grateful to any suggestions anyone can offer!
The house is located on the “wet side” of the Northern Rocky Mountains where we get about 100″ + inches of snow per year with a lot of cloudy days (5B/6B boundary). The winter temperatures generally range from -10 to mid 30s F. The roof is a simple gable design with a single ridge and no valleys. It is an 8/12 pitch with Fabral Rib metal roofing overlaying ice & water shield and OSB. The baffles are present and functioning. There is a properly installed ridge vent although we have had discussions as to whether or not it may be getting blocked by heavy snow. The metal roofing is laid over engineered scissor joists. In the attic space between the joists run insulated HVAC vents. There is R 50 bat insulation. The air handler for the single stage, variable speed heat pump is enclosed in a small attic which is insulated and closed off from the rest of the attic with OSB. The room below has a flat, drywall ceiling. Two-thirds of the interior ceiling is cathedral pine tongue and grove attached to the scissor joists. The remainder of the ceiling is cathedral but composed of drywall attached to the joists.
Three problems have plagued the house.
1. “Rain” inside which we believe is condensation that has collected in the insulation bats above the T & G.
2.Massive ice dams, some of which broke a lower roof which necessitated rebuilding the area under the lower roof.
3. High heating costs which we assume are associated with inadvertently heating the attic.
We are now preparing to undertake a major overhaul of the roof. We are prepared to take the exterior roof off and make major changes if necessary.
The methods that have been suggested include
1. “Foam the lid” creating a barrier between the attic and the exterior but continuing to have a semi-heated attic.
2. Place a waterproof barrier (e.g. visqueen, etc) directly on the attic side of the T & G and foam over that.
3. Remove or replace the T & G with dry-wall.
4. Install gable end vents with a fan.
I am afraid that anything laid directly on the T & G could cause moisture to build up potentially rotting the wood, even something like “membrane”. If we make the underside of the roof the barrier we continue to semi-heat the attic which (1) is wasteful and (2) may continue the “rain” problem due to condensation. I understand moisture could be removed mechanically or perhaps with convection but it seems senseless to heat and then vent to the outside the heated attic air.
My gut tells me to relocate the HVAC but I still don’t know how to deal with the air penetration from the T & G. Some experts at Green Building Advisor have disagreed about whether or not you can get a tight enough seal with rigid foam to prevent saturation of the wood. Additionally, removing the wood changes the house design aesthetic and would be very expensive.
I have learned a great deal about insulation and ice dams since battling this roof but I really don’t know how to fix the problem properly, environmentally, and once.
Thank you in advance.
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