I have a 1940 2-1/2 story home, the 1/2 story being an attic space with older batten insulation in the rafters covered by thin particle board. The old asphalt shingle roof had a ridge vent which kept when the new metal shingle roof was installed. Since the attic floor has minimal insulation, each winter I block up the ridge vent with solid foam insulation which fits tightly between 2x4's and cover with wood paneling. I did this for years with the old asphalt roof without issue. Now, condensation builds up and leaks into the attic.
The roof vent was installed to provide additional summer ventilation, which otherwise came only from two gable end windows and one dormer window. Should I simply seal up the ridge vent, and if so, how do I assure no more condensation gets in? I've considered a complete insulation tear-out and replace with spray foam, but since the attic space is accessed via stairway, it seems this would only provide a "semi-hot roof". Would this create other issues; and does the foam need a fire retardant cover? Getting drywall to the attic space would not be easy.
Guest User
2014-09-01 14:24:49.000000
Todd and Eric: When the old asphalt roof was in place, I did not have condensation issues. That roof was installed 15+ years ago and the ridge vent was put in at that time. The shingles failed after roughly 10 years and I replaced it with the metal roofing. Since then, we've had the condensation problem.
I've attached an interior picture showing the ridge vent area, the fiber board which covers the batten insulation and the 2x4 framing I installed when the ridge vent was originally put in. During the winter months, I put rigid foam insulation between the 2x4's (it fits tightly) and cover both the 2x4's and the wood studs with wood paneling. I've always done this to keep out the cold winter air (due to minimal attic floor insulation). The condensation seems to drip onto the rigid foam and eventually gravitate down the walls. So far, it seems to have stayed in the attic space.
Thanks for your assistance.
Guest User
2014-09-02 19:33:51.000000
Thanks. I am confused. I thought that sealing the ridge vent did not cause a problem before but now it does ... but then you ask me if you should seal it. Can you clarify.
Condensation in an attic occurs from moisture inside the home which does not get vented out and instead reaches dew point.
I look forward to hearing back from you.
Todd Miller
2014-09-01 14:43:31.000000
PRB,
Please post up some pictures when you can.
This house is vented and insulated improperly right now. The lack of permeability in the metal is probably lessening the release of the moisture and you need to address this before winter.
Post up some pictures and we will get you squared away.
Eric Novotny
2014-09-01 17:23:57.000000
The reason the shingles did fail was the lack of moisture management and trapped heat.
Your insulation schedule and air barrier isn't adequate in this case.
If the roof is not equip with a ridge vent and you can to leave that space as conditioned, you need to pull that insulation down and ideally spray foam that underside.
It won't be cheap but it is the best way to do it.
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