Mold around a window usually appears where indoor moisture condenses or rainwater leaks in. Prevention starts by separating interior condensation from leakage through the frame, seals, or exterior wall.
Notice whether it follows cold weather or rain
Droplets on glass during cold mornings point to condensation. Moisture that appears with rain even when indoor air is dry suggests exterior leakage.
Lower indoor humidity when condensation is the cause
Use kitchen and bath exhaust, avoid drying large amounts of laundry without ventilation, and allow air circulation near cold windows.
Repair failed seals and drainage details
Failed seals, flashing, or blocked weep paths can admit water. Do not caulk over drainage openings designed to let rainwater escape.
Do not paint over an area that keeps getting wet
Clean small surface growth with a material-compatible method only after correcting moisture. Damaged wood or drywall may need repair in addition to cleaning.
Sources
- U.S. Environmental Protection Agency — A Brief Guide to Mold, Moisture and Your Home — Moisture control, material drying, mold cleanup, and recurrence prevention.