Flat roof venting with no condensation issues?
Hello,
I’m trying to reduce the energy use in a 13,000 sq ft building. It’s a steel office building with a drop ceiling and 10″ fiberglass batts on top of the ceiling tiles. Right now the attic is used for storage of old files and gets very hot in the (very humid) Chicago summers (~90 degrees Fahrenheit). We also don’t have any attic venting that I’m aware of and there are no condensation/mold issues.
My question is: Will installing forced attic ventilation (Solar powered fans) be a wise idea? I’m not sure pushing 90 degree (and humid) air into a fairly low-humidity attic is going to save that much on cooling costs.
Please let me know any information I skipped over and I will try my best to provide it (total noobie, here).
Thanks,
Pete Koszulinski
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Replies
Pete,
1. The existing fiberglass batts laid on top of the suspended ceiling are doing virtually nothing. Their R-value is worthless because of air leakage.
2. Solar-powered attic fans will make the air leakage problem worse by depressurizing the attic and increasing exfiltration.
3. The solution is to install an air barrier and insulation layer at the level of the roof sheathing above the attic. One way to do that is to install closed-cell spray foam on the underside of the roof sheathing, although there are other approaches that work as well.