Q&A – Mold mystery

This homeowner reached out to the AskARoofer experts to help them make sure their attic ventilation is set up properly.

Paul, a homeowner from Pennsylvania, reached out having discovered black mold in their attic. They asked:

I noticed I'm getting black mold on the sheathing in my attic. I have ridge vents, soffit vents an gable vent. The problem is only on the rear of the house the north side. I have baffles at the bottom of each bay.

One of our roofing experts, Marty from Go Roof Tune Up responded:

Paul, You don’t have proper ventilation. 1/150 is the recommended ratio of square feet of vent area to square feet of attic space. 50% low 50% high. Also sometimes gable vents and ridge vents work against each other, however, it looks like your problem is at the lower area of your roof. Still good to check.

Double-check the area of the venting in the soffits and double-check that the baffles are clear.

Additionally, John Kenney of Cotney Consulting Group shared:

Different methods can be used to remove the mold growth, but the mold growth will return if the underlying moisture issues are not addressed. Typically, this involves increasing the roof ventilation and air-sealing the top floor's ceiling. Even with vents in place, the airflow might not be sufficient to remove all moisture. It's important to ensure that soffit vents are not blocked by insulation and that the baffles are properly installed to maintain an air passage. Sometimes, additional venting or better placement of existing vents is necessary. Consulting with a mold remediation expert who can visit your home can provide specific advice tailored to your home's unique situation.

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