Q:

We have a small double-glazed picture window in our kitchen. Last winter, condensation started to form between the panes along the bottom edge. What can we do?

Anne Summers, Brookeville, MD

A:

Roe A. Osborn replies: Short of replacing the glass, not a whole lot can be done about a double-glazed window with condensation between the panes. The culprit is a failed seal between the spacer that holds the panes apart and the glass. As the window warms and then cools, the air between the panes expands and contracts, and the failed seal allows moisture-laden air to seep in. You’re probably seeing more condensation lately because of the severe winter on the East Coast this year.

Eventually, the cycle of moisture condensation and evaporation will etch the inside of the panes, and the windows will be fogged permanently. You didn’t mention age, but if that window is 20 years old or more, it has actually stood up well. The good news is that in most cases, a glazier can replace the glass without replacing the entire window unit.

If the condensation is limited to a small amount along the bottom edge, I suggest waiting to replace the window. It might take years before there is significant fogging of the glass. But before you call your local glass contractor, it might be a good idea to verify that the window sash is solid. Quite often, as the sash begins to rot, it no longer supports the pane properly, and the seal is the first thing to go. If the sash is shot, consider replacing the whole unit.