Condensation issue with roof
Just got a call from a builder who recently completed a house I designed her in Ct. (zone 5). He didn’t install soffit vents or ridge vents since he was supposed to use open cell spray foam in the rafter cavities. Turns out he didn’t foam the rafters, but use fiberglass batts (with baffles) instead & is now seeing condensation dripping from the rafter tails & down the soffits.Air handlers & ducts are in the attic, so I’d prefer to keep the insulation in the rafters.
Potential solutions include:
1. Remove the batts & install spray foam in the rafters.Best solution in my opinion, but probably won’t happen due to cost & messiness as the house is now being lived in.
2. Install soffit vents & ridge vents.
3. Install soffit vents & a power vent. This is the roofer’s suggestion, but I think this would only remove air from the attic & would not work the same as a ridge vent.
Any comments on these solutions (or others) would be appreciated!
Thanks…….Brad
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Replies
Brad/John,
I certainly hope that the homeowner ends up with a code-compliant roof, regardless of the cost, in light of the builder's error.
A code-compliant roof needs to meet minimum R-value requirements, which are probably R-49 in Zone 5 (but which may be less if local codes haven't been updated recently).
The power vent is a very bad idea. In addition to wasting electricity, it will drastically reduce the thermal performance of the fibrous insulation -- from R-24 (just guessing) to something closer to R-1 (again, just guessing).
Here is a link to an article that explains all of your options: How to Build an Insulated Cathedral Ceiling.
+1 on power venting being the anti-solution.
How deep are the rafters?
How complicated are the roof lines? (any valleys, hips or dormers?)