Healthy Indoors Magazine - USA Edition

28 | July 2019 Ventilation Won't Prevent Attic Mold Growth ©2019, Jeffrey C. May growth on the attic sheathing at both gables, as well as on the gable-end wall sheathing. A moisture meter confirmed that damp-appearing spots on the sheathing were indeed wet, and I could even see some small spots of ice on the wall. The couple had two young children. Because they found that the hot-air heat made the indoor air feel dry, they were using a number of portable humidifiers, including in their children's bedrooms on the second floor. They told me that they estimated they were using several gallons of water a day to humidify the indoor air. That moisture was rising up into the attic through leaky pull-down stairs, leading to condensation and mold growth on the cool attic sheathing. I recommended mold remediation under containment to prevent the spread of potentially allergenic dust. The roof was older, so another option would be to install a new roof, replacing the sheathing at that time. The moldy rafters would have to be cleaned and sealed before installation of the new sheathing. The family also had to stop pouring so much moisture into the house, and cover the pull-down stairs with an airtight, insulated box to prevent moist house air from flowing up into the attic. Alternatively, the couple could have spray polyurethane foam (SPF) installed between the raf- ters after the sheathing was dry. This would encapsulate the mold and change the attic into a "conditioned" space. Prior to that installation, the plywood flooring and existing insulation would need to be removed, so that the floor fram- ing and ceiling drywall could be HEPA vacuumed and light- ly spray-painted to adhere residual, allergenic dust before new flooring was installed. My one cau on with SPF is that if improperly mixed or applied, the insula on can off-gas noxious odors, so an experienced company should be hired. In addi on, SPF must be covered with a fire-protec ve coa ng such as intumescent paint. I recommended that a DennyFoil barrier be stapled to the ra ers, and then drywall installed to cover the barrier and foam. The foil would prevent off-gassing, and the drywall would act as a fire-protec ve coa ng. In another home, the owner had been in residence for over 10 years. He called me because while he was having W e get a number of calls about attic mold, espe- cially during real estate transactions. Ironically enough, a building occupant is much more apt to be exposed to spores from mold growth in a basement than in an attic, because air in a house flows from bottom to top and out, especially in the heating sea- son. Still, in a house with central A/C, there may be leaky ducts in a moldy attic, or an air handler with a filter holder that isn't airtight. Then spores from attic mold growth can be entrained into the mechanical system. And occupants who use the attic for storage can disturb mold growth. Once it has been established that black staining on attic sheathing is indeed mold growth, the first question to ask is: why is it growing and/or why did it grow there? (Due to high summer temperatures, such mold growth is often dead, but that doesn't mean it's no longer allergenic.) If this question isn't answered, a lot of money can be spent on remediation, and the mold growth will most likely return. Attic mold growth near a bathroom vent May Indoor Air Investigations LLC I worked with one young couple who moved into their new home a few months before they called me. Neither of them saw mold in the attic during the home inspection or when they moved in. Yet when they went up into the attic in mid-December to retrieve their stored Christmas decora- tions, they saw dark black staining on the sheathing. The wife had allergies and so was concerned. I could see mold

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