Should I add more venting to my attic, or seal it up, or do nothing?
Should I add more venting to my attic, or should I seal it up and run a dehumidifier to prevent mold, or should I do nothing, or should I go with some fourth option? I read the “All about attic venting” article, but it doesn’t leave me certain about how I should proceed.
GENERAL DETAILS: My home was built in 1965, is in climate zone 2A (Austin TX), has 2000sf of attic floor covered with blown-in insulation, and has a sheet-metal roof covering an asphalt-shingle roof with no insulation above the sheathing or between the rafters.
VENTILATION DETAILS: There is a 4sf gable vent on the north side, and a 0.8 sf vent on the south side. Yes, that’s barely any venting. I presume that prior to a 2F addition in 1982, there was another 4sf gable vent on the south side. There are no soffits (see picture), so no easy way to add intakes there. There is no ridge venting.
MOISTURE DETAILS: There is no basement. No bath fans vent into the attic. No special efforts were made by the previous owner to seal up the ceiling penetrations but I intend do, though the roof is pitched so low I won’t be able to get to the edges to seal the top plates to the drywall there. The attic has leaky ducts but I plan to install a heat-pump minisplit system and seal up the registers and return.
I wouldn’t be venting to lower cooling bills or keep the attic dry, since I know venting won’t do that. If I vent, it would be to keep air circulating through because stagnant air is conducive to mold. However, I observed no mold in the attic, so if mold hasn’t been growing there over 51 years then it’s likely not a concern–and that even if mold formed, if it were confined to the attic, it’s probably not a health risk for the occupants. Perhaps I can go one step further and just seal the attic up completely to keep moist air out, then run a dehumidifier to keep it dry. Once the attic is dried out, I assume it should stay dry enough that the dehumidifier won’t kick in very often so I wouldn’t be using much electricity to power it.
So, should I add more venting to my attic, or should I seal it up and run a dehumidifier to prevent mold, or should I do nothing, or should I go with some fourth option?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part