Attic moisture problems
I live in Oakland, CA, near San Francisco. I have a 1920s building with a low-slope roof, 1.5” in 12, and an unvented attic with R-30 cellulose blown in. The ridge is roughly 3 feet high. A new roof was installed 8 years ago.
Recently I noticed mold in the attic on the roof sheathing and sides of the joists. There are no water leaks so I am lead to believe this is a condensation issue. I want to remediate the mold and want to make sure the mold does not come back.
I believe I have 3 options:
1) Re roof with foam board insulation
2) Spray foam insulation to underside of roof or Flash / Batt
3) Seal ceiling airtight and vent attic.
Option #1 is costly as I still have to remediate the mold.
Option #2 encapsulates the mold but I am not sure about access to perform the work and removing the ceiling might be my only option. Are there any other concerns to consider with this option, i.e. creating a “sick house” since roof is now airtight? Would I still need venting?
Option #3 appears to not be as efficient as #2 but may be my only option.
My walls are not insulated, will this affect the airflow into the roof? Do you see any issue venting in a low slope roof? I would be adding soffit vents according to code, but what type and location of exhaust vents would you recommend? Should an exhaust fan be an option?
Thanks for your help
Posted Thu, 10/31/2013 - 23:36
Edited Fri, 11/01/2013 - 05:01
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