Q: Why does mildew form on the eaves of my house, right near the vents, but not in the attic? I was worried about this, then checked the...

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Why does mildew form on the eaves of my house, right near the vents, but not in the attic? I was worried about this, then checked the attic and it was free of mold.


Cold air entering, or hot air exiting, the vents provides just the right temperature for mold to form at any given time. Lots of air movement here also helps. You can see this on top of a roof near vents, too. This phenomenon is not unusual, actually.

You may also see this from time to time on siding on the walls of houses, making the location of the studs obvious. The cavities between the studs are insulated and are cooler than the “thermal short circuit” the stud provides. That small temperature difference on the studs provides exactly the right temperature for the mold to form when the correct moisture and airborne spore levels are present.


In looking at many 1980s houses with aluminum windows, I have seen a lot of windows that have sweat between the panes. I assume this is a failed seal, causing condensation and a dirty look to the glass. My question is two-fold: Is there any way to repair it without replacing the glass? And secondly, why does it seem to happen mostly on fixed panes, not sliding units?


I’m not aware of any way to fix the problem short of replacing the glass. I had heard about a repair process years ago, but I have no idea whether it got off the ground or how successful it was. If any readers have information on this, I would love to hear about it.

I hadn’t noticed that the condensation is mostly in fixed panes until recently, when I started making mental notes. Maybe fixed panes do not allow the seal and frame to expand and contract during changing temperatures. Let’s hear from the readers: What are your experiences?


I own one of those “Bellevue chateaus” built in the mid- 1980s — you know, steep cedar shake roof, wood windows, tall entry and three-car garage. Several of my neighbors and I have the same issue with rotting window frames in the living room. There is a bay window there, and no one has found any leaks in the window, roof or brick sides. Why do the windows rot there but nowhere else?


This is a very common affliction with that style. Your roof over the bay window has no gutter, no roof overhang, and they top it off by installing wood windows resting directly on brick (no flashing beneath). The brick soaks up the moisture like a sponge and spoon-feeds it to the window.

The lack of gutter and overhang is an aesthetic thing, so you don’t want to change that. But when you replace your window, treat it with wood preservative (compatible with your choice of paint or stain) and add a large piece of flashing over the top of the horizontal brick; that will prevent rot from recurring.

But the window might be salvageable. If it is, use a borate treatment and wood filler.

Tinted windows:

After last week’s mention of tinted glass, several readers reminded me that tinting might affect the warranty on newer windows or on windows that have a lifetime guarantee. Some window-tinting companies may offer a superceding warranty. Be sure to check with your window maker and tinting company before proceeding. Another reader asked, “Why does no one use traditional curtains anymore? They work great at blocking sun.”

Plunging in:

I recently tested a Jet Plunger, a fine device that eliminates the up and down movement of a traditional plunger. It works like a bicycle pump. One shot of compressed air in the bowl and the job is done. No nasty splish-splash up the sides. Put it in place; pump the handle while the base stays steady; whoosh; and rinse it off. Jet Plunger, $24.95 at www.jetplunger.com, is starting to show up in retail stores around Puget Sound.

Darrell Hay is a local home inspector and manages several rental properties. He answers reader questions — call 206-464-8514 to record your question, or e-mail dhay@seattletimes.com. Sorry, no personal replies. More columns at www.seattletimes.com/columnists.