At a recent home inspection on Orcas Island, I discovered plywood sheathing in the attic that was stained with a mold-like growth. This typically, almost always, indicates an insufficient ventilation or elevated moisture issue within the attic. Vents could be restricted, vent ducts may be discharging into the attic, or the interface between the main home and attic may need to be better sealed. In any event, a contractor needs to first resolve the underlying cause of elevated moisture and make necessary repairs. The mold-like growth is then typically remediated with a mildicide and then painted with mildicide paint to encapsulate historic mold growth. I recommend tinting the paint TAN because white or black mold growth will be obvious if it returns (e.g., you’ll see it on tan paint). If the attic is forever tan, you know the issue has been addressed satisfactorily. Because most home buyers want this issue addressed prior to closing, and remediation can be expensive, I recommend peeking into your attic on an annual basis and dealing with any apparent mold-like growth sooner than later if noted.