Posted By Lbear on 17 Mar 2012 05:38 PM
NREL Study
Question:
In lieu of ridge vents, do they make a switch-controlled mechanical damper that homeowners could control unwanted infiltration by cutting off the attic vent with a wall switch during heavy winter winds?
That is an interesting report, and I agree with jonr's comments.
In terms of a "switch-controlled mechanical damper," that is somewhat like an attic power vent fan. Those fans typically have a thermostatically controlled switch at the fan that turns the vent fan on at 110 F, or whatever the homeowner sets the thermostat at. On a house that I owned, there was also a power switch inside the house that could be used to shut off the power to the fan.
The arguments made on this forum against power vents are: (1) they apply a negative pressure to the attic that can suck conditioned air out of the house into the attic, and (2) they consume electrical energy when operating. I would add that it is uncomfortable to change out the fan motors in a blazing hot attic when they wear out.
Concerning the NREL report, it was interesting. I would add to their comments the following. Having a conditioned attic would make it much safer to do work like running cable TV wiring, etc. in the attic on hot afternoons. On the other hand, it seems much easier and cheaper to upgrade insulation by adding it onto the attic floor than adding it to the attic sealing, and it seems like super insulation levels would be more practical on the attic floor. The report states that sealed attics have higher roof temperatures, and these higher temperatures would reduce the lifetime of asphalt shingles. Reroofing is a major maintenance cost in hot climates.