I'd sure would really appreciate any input, and thank you ahead of time. I'm an engineer, and looking for a retailer that uses this product. It is a double pane with LoĒ-i89 and LoĒ-i366 units, which results in 77% visible light transmission, 0.21 U-factor, and 0.62 Solar heat gain. (with Argon fill) Yes, it is for a window that never sees sun, in a Northern very rainly climate. The glass cell vendor is Cardinal Corporation. Specs are detailed out here: http://www.cardinalcorp.com/products/coated-glass/loe-i89-glass/ Low U value, high Light Transmission are the most important to me. High Solar Heat Gain is fine, it is a North window. Any advice on window frame material is much appreciated, most of the current ones are aluminum, and haven't had good luck with vinyl that are on a few. I also have a very large south window that I am considering the double pane LoĒ²-270, LoĒ-i89- U-factor 0.20, Vt=69%, Solar heat gain 0.36 window cell. Thoughts? Anyone have experience with the Cardinal Neat® (naturally clean glass)? I'm considering this for the second story.

I recently purchased Marvin Integrity All-Ultrex (fiberglass frame) windows with Cardinal LoE-180 high solar gain glass. You can check with your local Marvin window supplier and see if they can get the LoE-i89 glass package. This LoE-i89 must be a new product because I don't recall seeing it when I was researching windows a few months back.

I see now that the glass you are quoting performance numbers for is a Cardinal LoE-180 double-pane high solar gain glass with a LoE-i89 coating on the 4th surface. Your local Marvin Integrity dealer should be able to get that glass.

The Cardinal LoE-366 double-pane low solar heat gain units with LoE-i89 coating has the lowest visible light transmittance of the Cardinal products.  It has the following performance numbers per the Cardinal website:

Visible light transmittance = 63%
Solar Heat Gain = 0.27
U-Factor (w/Argon) = 0.20

http://www.cardinalcorp.com/products/coated-glass/loe-i89-glass/

http://www.integritywindows.com/Fiberglass-Windows/

I would put the high solar gain glass (LoE-180 + LoE-i89) on the south side if you want winter time solar heat gain. I wouldn't think that having the high solar heat gain glass on the south side would be a huge negative factor in the summer in a northern climate, especially if you have any shading from roof overhangs or trees. I put the high solar gain glass on the south side and I am building in Arkansas where it gets pretty hot in the summer, but I have roof eves and shading from trees that will block most if not all sun from the windows in the summer when the sun is nearly vertical in the middle of the day.

Where I can see the LoE-366 low solar heat glass being of benefit is where you have a lot of glass on the west side of the home. This would reduce summer time afternoon heat gain where the sun shines directly on the window.

Okay, thanks for the advice.

Are those specs for the Cardinal cell glass (LoE-180 + LoE-i89), considering visible transmission and U-Factor (for North side windows), pretty much leading the industry for double pane windows, or is there something better?