Failing Window Seals
Help for foggy sashes
We're about to spend a lot of money on replacement windows. The existing aluminum-framed, double-glazed windows are only about 15 years old, but the seals on two of them have failed and the glass has fogged up. We're considering wood-framed, double-glazed units
with low-e glass. But is this plan worth the expense if the seals are going to fail in another 15 years? Our heating costs aren't really that bad.
Barbara, Longbranch, Washington
Tom Silva replies: Moisture between the panes of a double-glazed window is a sure sign that the seal around the perimeter has broken. Fogging alone doesn't hurt the performance of the window substantially (unless it has a soft low-e coating), but it doesn't look good. Unfortunately, the only way to get rid of the fog is to replace the sash.
The question is: Do you really
need double-glazed replacements? There's no way to predict how long a
glass seal will last because so many things can make it fail, including
poor installation, strain caused by building movement, high winds, and
the careless use of a heat gun when stripping paint. Some manufacturers
even warn of damage from pressure washers, window-cleaning chemicals, and sun-reflective window films. The best warranties on window seals these days are for 20 years. Considering your relatively mild climate, double-glazed low-e glass probably isn't worth the premium you'd pay.
If I were you, I'd buy single-glazed wood windows and protect them with good-quality wood or metal storm windows. (If you're anxious to keep your drapes and furniture from fading in the sun, both windows and storms can be fitted with single-pane, low-e glass, which will also give additional energy savings.) Together, single-glazed windows and storms, or single-glazed units with storm panels attached to the sash, provide
energy performance comparable to a double-glazed unit at much less cost. And there's no chance of seal failures.