Mold in Attic

Paul in Pennsylvania asked:

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

Marty from Go Roof Tune Up said:

Paul, You don’t have proper ventilation. 1/150 is the recommended ratio of sq ft of vent area to sq ft 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.

Let us know what you find.

John Kenney of Cotney Consulting Group said:

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.