While my intentions are to replace the aluminum windows in our home with something more efficient in the next few years, I now have the short term task of deciding on what to do in our extension that has commercial-style windows. The 21' x 16' room has no walls, 6x6 posts only between 6 windows and a sliding door. Majority of windows are 90" wide by 70" high dual pane non-opening, 2 have a 14" sliding section at the bottom. The addition was built 35yrs ago and I can only guess the windows are original but some glass have a newer date inside the frame. I have to change out 2 failed glass and have been inquiring about changing the windows completely. One window company suggested changing everything with newer vinyl windows while the other left without sending an estimate as he suggested that unless I didn't like the look of the frames, the minimal benefit from aluminum to vinyl was not worth the expense given the amount of glass in this particular case and get a glass company to quote better glass. The glass company can change the glass but they are older, thinner cases. and not as efficient as thicker more modern ones. Not sure who is looking out for my best interests long term. Your thoughts? Also, Is it possible to replace the inside snap-on window stops with a custom wood stop to allow me to put in the thicker glass section? would it affect the frame's rigidity? or maybe help cold transfer? The stop with seal is 2 inches wide and the distance from the inside glass to the frame edge is 2 3/8" Thanks in advance, G

I think your best bet is to just replace the glass in the commercial frames. If they currently have double pane IGU's then there is no real benefit in trying to re-engineer the stops to get "thicker glass section". Thicker is not necessarily more energy efficient. Spending the money on getting the appropriate glass coatings is probably a better deal than messing with the frames.

I had to replace almost all the IGU's on my 18 yo house and was able to do the work myself. Not much to it once you get a couple under your belt. Buy some good suction cups, try some of the little ones first, get help on the bigger windows (they do get heavy). Snap-on stops are readily available if you break some, and I got my IGU's on line at One Day Glass (was cheaper than my local supplier, 50% of the cost is shipping). The right glass for the use/orientation is the best bang for the buck IMHO.