Hello, I have a large sunspace/sunroom that I'm renovating that was originally built in the late 70s. Basically the design is 3 walls of vertically-mounted glazing--specifically 24 34" x 76" double-glass factory-sealed units. We needed to re-do the framing, so we removed all 24 back in April. 16 of the 24 were still good; the rest had lost their seal over the years. Yesterday I started to do a final cleaning/inspection of the 16 "good" ones and found that all but one had lost their seal too. I'm guessing that the reason is that a few weeks ago my contractor moved the 16 "good" ones from a shaded area to the east side of my house while he was doing some other construction work. From what I've read, these insulated units should never be stored in the sun. I'm guessing they heated up and this ruined their seal. So now I'm looking at another $2500 to replace these additional 16 failed glass units. But I'm also stepping back at this point and wondering about the durability/longevity of these factory-sealed units in general. I mean I get the idea of not leaving a stack a windows in the sun, but at the same time...it's a *window* for a *sunroom*, so I would have assumed it could handle some of this (it wasn't a particularly hot time of year or a location that would get more than the morning sun)... I've read about "site built" double-windows where two panes are used; the inner pane is sealed tightly from room air, the outer pane is "vented" to the outside. This sounds like an intriguing way to re-use all of these failed units I have, but the installation sounds a little tricky. And I guess I'm unclear how I could expect a different result than the foggy-inside failed units I have right now. I suppose the easiest thing is to just 'bite the bullet' and spend the money to replace all these units...but any thoughts/advice appreciated! PS my location is 69341 (western Nebraska), USDA zone 4-5