Oberon - thanks for that info! But I still don't know which to choose for these 5 bedroom windows...

The U value is not much different between the two which is your defense against the cold. You will get much more protection against the heat in the summer but less visible light transmission in the winter with the 366. Which is more important to you? That should be the deciding factor.

I'd recommend the 272. The extra solar gain in the colder months can be a benefit. The 366 will provide a little bit more comfort in the summer, but the 272 should provide superior efficiency when all is said and done. I tend to agree with skydoggy.

Low-e 272 on the South facing windows.

You can use Low-e 366 on the other elevations.

Thanks for all the great advice. Another thing I thought about, especially in response to Eastbay10's message above, is that winter here lasts 8 months or so, versus a short summer. So winter considerations should have more weight in this decision and 272 glass would be better. On the other hand, I will say that even in the winter, that bedroom gets very warm on a sunny day, due to its unobstructed 3rd-floor SE exposure. So in that case, perhaps 366 glass would be better. Sigh.

I am concerned about the amount of tinting I might notice with the 366 glass. I love my view of trees and sky out these windows, and wouldn't want that altered or diminished. And, it should be noted that right now I have 1991 Pella Prolines with clear glass, rotting sashes and tons of draft. So new Marvin Ultimates with 272 glass would be such an enormous improvement. Relative to that degree of improvement, windows with 366 glass may only be a small margin better than 272 against the sun so as not to be noticeable except for more tint of my view. What do you think?

Any other advice or response to my thought process would be welcome.

This post was edited by Mrs_Nyefnyef on Sat, Sep 28, 13 at 13:31

In response to your latest message, I agree that 272 would be best for you. It will be considerably more efficient against heat than your current clear insulated windows and give you the winter benefits as well.

When looking at small samples of the different glass/coating types, the LoE coatings can look dark, but when you have them in an actual window in a home environment very few people really notice that there is a coating at all.

It's much more common for people to question if the window company forgot the coating since the homeowner was expecting to be able to see it - and they can't.

Since you live in a heating dominated climate, I agree with the previous posters that you will appreciate the advantage of higher solar heat gain in the 272 coating.

This post was edited by oberon on Sun, Sep 29, 13 at 9:00

Thanks everyone. This forum is great. LoE 272 it is!

Is the 272 better because she is SE, or should all windows be 272 regardless of direction? I am in Minnesota and read a previous gw thread where somebody said 366 is better for none south facing windows. I have no windows on the South side. So was curious what you guys thought.

272 would be better in her case because of the passive solar heating potential. Being in a heating degree dominated climate, you want to allow for as much of the free energy to enter the home through the windows in the winter months.