[serene911]

I've got 40 years in the custom artglass business and have ran insulated units
as part of many projects. Sales people like to sell the argon as an upcharge.
The guys in the shop that I know who actually run the units don't think it lasts
more than 6 months. Stick with Low e which has a proven track record of actually
doing something. When you convert the u- value of a window to r- value as in the
consumer report article, the added argon is inconsequential over a regular insulated
glass unit with a low e coating. Most of your heat loss is straight up through the
ceiling anyway.