Attic baffles–My ProVent modification. Or not . . .
As detailed in previous posts, I am now working to improve the efficiency of a 1950 Cape Cod style house. One major “challenge” of this style of house is the heat transfer through the sloped ceiling area upstairs. The summer heat can be especially problematic. My house has rafters that are 6″ deep, which doesn’t leave much room for insulation. I wanted a vented roof assembly, and decided to compromise and use the approx 1.5″ deep ProVent baffles/chutes in this space. Site-built baffles with polyiso trays would have offered better insulation and a potentially deeper vent channel, but I am concerned about flammability issues.
My two initial qualms about ProVent:
Cost: The 14.5″ wide vent costs $2 for 48 inches, so about $5 for each of my rafter bays in the “cathedral slope.’ I know this may not seem like big bucks, but it’s considerably more than the cost of the fiberglass insulation that will fill the rest of the bay. Seems crazy.
Color: Why are these darn things black? In the summer they will absorb IR radiated energy very efficiently from my hot roof deck and transfer it directly to the top of the insulation.
To deal with the second issue, I installed a layer of aluminum foil loosely in the channel, suspended from the sides and drooping into the trough. Reflective on top (but would eventually get dusty there) and low emmissivity on the underside, so low radiated heat transfer to the Provent (and my insulation). Cheap, and easy. I got about 10 of them installed, and was pretty proud of my modification. Then a slight breeze outside set the foil to rattling and rusting. I don’t know if it would have been audible inside after the insulation and drywall was in, or if it could be heard outside. Anyway, I couldn’t take the chance–there’d be no going back once the FG, polyiso under the rafters, and drywall is up. So I ripped out my great invention.
I still wonder why ProVent isn’t shiny, or at least white.
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