[axiolite]

> But in the winter, you'd want to allow that radiant energy through, which the low-e glass is not doing.

Low-E glass reduces inside heat radiating to the outside, too. You can find many articles online discussing the advantages during winter/heating season if you look.

I tested a couple years with/without a tinting film on my west-facing windows (under mini-blinds) and noticed a very, very small increase in winter heating costs, with a big decrease in summer cooling costs, and more consistent temperatures throughout the day in both seasons, which is a benefit in itself (you can use a lower-capacity HVAC system). I suspect a proper upgrade to low-E windows (or at least tinting ALL my windows) would have done much better.