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Mildew keeps showing up at the lower window-frame corners
What clues help tell whether mildew at a window’s lower corners is from room-side condensation or water getting in through the window’s drainage path or installation? The location seems important: growth on the room-facing frame or glass might point to a different moisture pattern than dampness in the track or beneath the trim.
Does the timing help distinguish them, such as moisture appearing during humid weather even without rain versus showing up after rain? I’d also like to know which non-invasive observations can help trace the source without blocking drainage openings or taking the window apart.
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Where the moisture first shows up matters, but rain timing alone doesn’t prove the source. Room-facing glass or frame that gets damp during humid weather, even without rain, points more toward condensation. A wet track after rain may be part of normal drainage; moisture extending beneath the trim or onto the room side points more toward water getting past the window. Either pattern is a clue, not a verdict.