dean wrote:
Are they air tight? I mean, even after several years they still don't
get misted up inside, but I can't imagine how (with all the cold and
warm contractions and expansion) they ever manage not to leak somehow?
Am I missing some kind of magic here?

TIA!

Dean

Yeah you are? You've missed trying to take the
panes apart. Suggest you try. They will leak
eventually, but sliders should last 15 or more
years. The old non movable Thermopane windows
easily last more than 35 years.