4. Moisture and Mold
When an attic is not vented properly and warm moist air rises, that warm air can get trapped in the attic. Once this happens, condensation develops on the underside of the roof, causing rusty nails and, eventually, mold growth.
Unfortunately, if left long enough plywood can rot out and you’ll need a new roof.
It can happen with new or old roofs as sometimes this is due to over-insulating, which blocks some of the vents. Just like a car, a home needs an appropriate intake (soffits) and exhaust (ridge vent).
As mold and mildew are an extremely intense health hazard, it’s extremely important that your roof has proper intake and ventilation.
You should act now to impede any extra costs of replacing all damaged wood as well as mold remediation.