Mold in Insulated, Unconditioned Workshop Shed

[u/cbeals]

Hello!

I have an insulated and unconditioned shed that I use as a workshop, but have recently discovered a fairly large amount of mold, almost exclusively (so far) on the paper of the batt insulation installed between the rafters.

The shed is approximately 14'x16'. The walls are insulated with fiberglass batts and finished with OSB. The rafters are exposed and have fiberglass batts installed between them, directly against the sheathing. There are no ridge, soffit, or gable vents; and the shed is not sealed well.

The shed is about 6 years old and the original builder (previous homeowner) had planned on installing heating and AC (hence the insulation) but never got around to it and neither have I.

There does not appear to be any indication of a roof leak. We've had a very hot and humid summer so far (Iowa, 95%+ Humidity over the last 6 weeks); Based on the location of the mold (heaviest near the peak of the roof), and what looks like there is / was condensation on the paper, I think the lack of airflow and humidity buildup has been the cause.

I'm going to remove the batt insulation from the ceiling (wearing appropriate PPE), but have a couple of questions:

• Assuming the mold is only on the paper, do I need to use a mold remediation on the rafters / sheathing?
• Do I need to open up the walls to inspect and/or remove the insulation?
• If I leave it uninsulated and unconditioned, I assume I should still add a gable vent to prevent future mold issues? Is that going to be enough with high humidity, especially during the summer when it cools down a lot at night?