double glazing revisited, historic windows, Connecticut winter.
The certain eventual failure, and high price tag of IGU’s makes them very unsavory to me. They also look very ugly compared to beautiful old wood windows, I think. Even the best commercially available insulated windows with divided lites do not have the right proportions to match the very narrow muntins of old windows, often as narrow as 5/8″. The depth is also too shallow from the top of the muntin to the face of glass- just doesn’t look right on an historic New England home.
If one happens to be a professional millworker, which I am, one can address the issue of the looks by making one’s own tall skinny muntins, hiding the wide and ugly glazing seal inside the perimeter of the sash so you don’t see it (just like this guy does: http://www.heirloomwindows.com). But that still does not address the issue of longevity. I don’t want to have to go through the whole process every 20 years or less, when the seal in my glazing fails, which we all know it will.
Why bother, you ask, when you could just add a storm window? I’m speaking here about divided lite glass doors (French doors). They are really beautiful and everyone loves them, but they are problematic. Storm doors are one solution, but they are without doubt a real pain when you’ve got armfuls of groceries: you have to hold one door open with your butt while you open the second door. Don’t you hate that?
Therefore: how about adding a second pane of glass with a spacer in between, but making no attempt to seal it? I can’t find any information on this system, how well it performs compared to single glazed windows with storm windows for example. And if we’re going to go that route, what’s the best way of stacking up the panes so you don’t get condensation?
When I was gutting my old house, I found some replacement windows which had amazing glazing: two layers of glass, fused together around the edge with yet more glass. The sightline was very narrow, compatible with shallow rabbets and skinny muntins. I looked it up, and found that this was the original Thermopane, the factory now shut down. Maybe we can bring this system back. I, for one, would gladly sacrifice a small amount of thermal performance in exchange for good looks and longevity. How do you make that stuff??