What exactly does "Low E" do? I've seen it sold in home windows for years, and I know BC Greenhouses offers it as an option on their double-pane glass glazing.

Supposedly it makes things warmer in winter and cooler in summer. I know Low E is more "reflective" and I guess the idea is it reflects the IR radiation INSIDE the GH to keep it warmer, and keeps the extra light out in summer to make it heat up less. In fact BC shows a lower light transmission for Low E vs. clear glass which makes sense.

So - does it work? And - does it REDUCE passive solar heating in cooler weather when you actually WANT it?

I could forsee a compromise where the roof is Low E and the sides are not - so the low angle winter sun is less interrupted, and the high-angle, hot summer sun more tempered.

Thoughts?