a glazing question

There is a local guy selling used glass doors from a gas station. The ones that are insulated for the beer or pop. Would that type of glazing be a no no as far as SHGC? I was also thinking of using one of them as the top to a batch solar water heater. any comments? Thanks in advance, Gary

I am no expert but I do not see why they wouldn't work.

I think I'll buy a couple since they are only $20 and if anyone knows a way to perform a homemade SHGC test on them I'll try that out. I wouldn't want to put them on my south wall if they aren't .5 right? But if they are much lower I guess I could use them on east or west.

Tough to pass up such a deal but how you build the jambs or incorporate them into your framing will also make a big difference in the performance. Airtightness is the most important part and if you could somehow insulate the outside edges of the window frame, that would help to.

As for testing, perhaps you could call around and find a home performance contractor with an actual tester. http://www.inspectortools.com/Solar-Gain-Low-E-Detector-p/edtmae4600.htm

If you could find some greenhouse glass you could probably rig up a decent enough test to suggest the performance difference. I suspect that those windows would have even higher iron content than typical low-e windows. You can really feel the difference standing behind a typical window and a high SHGC window in the sunshine. You could add more glazing per square foot to make up for the loss but the problem is the extra glazing will lose considerably more heat at night or cloudy periods. Movable insulation or insulative curtains could help combat this effect..