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Cause of attic mold

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I just installed new sheeting / osb,vapor barrior.metal roof panels, ridge is vented as well as soffit, attic is well insulated except for the access to attic, i just opened it up since new roof job and noticed mold on the north side of house, my house  in the shape of an L with the front facing north, the only side with some mold growth.

Could the mold have grown the hole length of the north side from the attic access not being well insulated ?

What would you reccomend at this point. The roof is just about 1 yr old. It is a 6/12 pitch. The old roof had no sheeting no vapor barrier and no insulation and I never had a mold issue. It was tin panels nailed onto purlins over rafters. Kind of dumb founded.
asked in Attic Area by sc7254 (120 points)
edited by darekrudy
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1 Answer

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Hi SC7254,
Without roof decking your attic was most likely colder / less air tight than it is now, therefore, there was no condensation and mold. Assuming that you have proper type of vapor barrier for you climatic zone, sufficient amount of insulation, enough and correctly distributed lower and upper vents, and properly balanced air flow between the soffits and the ridge vent, the next step would be to increase that air flow.
Some attics, especially in colder climates require more than the minimum amount of ventilation. If there’s no room for additional vents (you already have continuous soffit vent and full ridge vent) you may need to go with a humidistat and thermostat equipped attic power vent
Unless your access panel is heavily leaking conditioned air into the attic space I doubt it would be the only reason responsible for the mold growth.
answered by darekrudy (21,730 points)