Brian Lent has discovered something in his walls that no homeowner wants to see: mold.
Preparing a ground-floor room for drywall, Lent pulls some fiberglass batt insulation from a 2×6 stud cavity and notices the back side of the OSB sheathing is damp. A moisture meter reveals that in 80% of the bay, the moisture content is 66% or higher. Moisture and mold are heaviest at the bottom of each bay.
“Interestingly,” he writes in a Q&A post at GreenBuildingAdvisor, “after a panicked weekend a few days ago thinking we had an exterior leak, and much research on the internet and from GreenBuildingAdvisor, came to the consensus that it’s a cold sheathing condensation problem.”
His house is in the hills of Seattle, where winters are slightly colder than they would be downtown. The 400-square-foot room in which Lent is working is really a half-basement. It had been left unfinished and was serving as a mechanical room for HVAC equipment, including a furnace with an attached humidifier, and two gas hot-water heaters along with two 8-inch duct supplying outside air. He also discloses that he’s been running a humidifier during the winter to make indoor air more comfortable.
His remediation plan, already underway, includes killing the mold with a disinfectant, drying out the materials with heat and dehumidification, and then reinstalling the R-19 batts. He’ll finish the walls with mold-resistant drywall, a primer, and two coats of latex paint.
Is he on the right track? Or is there something missing from this equation? That’s the focus of this Q&A Spotlight.
The humidifier is a big mistake
Indoor relative humidity in his area should average about 30% at 70 degrees F during the winter, writes Dana Dorsett. “The only way you would ever need to add humidity…