Does the "low-e green glass" refer to the fact that the glass is earth-friendly or is it so named because the pyrolytic coating is actually bonded to a green substrate? It makes a considerable difference. Al For more information, search this forum using the search words tapla low-e

Hi sapote, I also agree that restoring these windows is much better than replacing. They are architectually unique and should remain as part of the home. In your environment, and based on your concerns about "reduce the glare and solar heat into the house during summer", you should be more concerned about Solar Heat Gain Coefficient or SHGC than about U-factor. Note that in the article that you referenced they were talking about 5/8" or 1" insulating glass. How much space do you actually have for an IG unit? The thinner the airspace between the lites, the less effieicnt the IG unit. But, as I said, you should not worry about U-factor so that is less of a concern. The way to block direct solar heat thru your windows is by installing a LowE coating - as you have found from your research. But, not all LowE coatings are the same. You need a Low Solar Heat Gain or LSHG coating applied to the #2 surface of the IG. The LowE coatings with the best perfomance numbers at blocking heat and glare are generally tinted coatings - not tinted glass, that is a different material - but tinted LowE coatings. But, if you don't want tinted windows (glass or coatings), then you will want to investigate the newest LSHG coatings on the market which have 3 layers of silver in the coating. One example is Cardinal's LoE366. I mention Cardinal's coating because it was the first of the triple-silver coatings on the market and it is the most likely coating that you will find for the residential market. Again, U-factor is not the issue in your situation - although you will get some improvement by changing to and IG unit versus single pane, it won't be nearly as much as you might be expecting - SHGC is the more important issue with your situation. You can significantly improve your SHGC numbers by installing an IG with a LSHG LowE coating.

Thx all - Todd, not sure I understand the ramifications of your first sentence - sounds like you mean the low-e would not be effective as a single window on an enclosed porch - not worth the extra $$$? Due to how the porch was constructed, its quite OK as a porch but to make it into a sunroom or more integrated with the interior would require extensive work - the next person can do it if they want! It faces north too which means as a sun room, the total lack of sun in the winter would be a definite problem LOL!

Go here: https://www.energystar.gov/products/building_products/residential_windows_doors_and_skylights Click 'Buying Guidance'. Click 'Determine your Energy Star Climate Zone'. Enter your state and zip code. Your Energy Star climate zone, U-factor, and SHGC will appear for windows and doors. Make sure that the windows and doors you select meet the Energy Star criteria. You can search for windows and doors in your climate zone here (http://essearch.nfrc.org/) but it gets complicated fast. It's best to decide what types of windows and doors you want and contact local resellers. Example manufacturers and products: Marvin Essential Provia