A three-season cabin built in the 1940s became a year-round dwelling two years ago, but owner Marty Pfeif has discovered an alarming problem: a bumper crop of mold in the attic.
In a post at the Q&A forum, Pfeif ticks off the particulars, including no apparent attempts at air-sealing, “shake and rake” R-19 insulation on the attic floor and some batting against the walls, no vapor barrier, and a ridge vent but no gable vents.
In addition, he’s recently learned that an exhaust duct for the bathroom fan has fallen apart, allowing moist air to spill directly into the attic for the last couple of years.
“This week I found mold in the attic, and lots of it!” he writes.
“I’m spraying the mold with bleach, and have ordered RMR 80 mold remover,” Pfeif continues. “I have removed a 12×5-foot section of insulation, and I am in the process of air-sealing this section.”
When he’s done, he’d like to have a more usable space, either for storage or possibly for use a loft.
“The house is only 600 square feet,” he says. “It has vaulted ceilings everywhere but the bedroom and bathroom. I have no idea if mold is growing in this part of the roof. I plan to hire a new contractor, but this time I want to know what should be done, instead of blindly trusting that they will do the job correctly.”
Air leaks are the problem
The cause of the problem is no mystery to GBA senior editor Martin Holladay, who writes, “The most likely cause of the mold is air leaks in your ceiling. These air leaks allow humid interior air (conditioned air) to enter your attic. The moisture in the air condenses on cold attic surfaces, encouraging mold growth.”