[MRM]

I can't don't know specifically how anyone's low energy glass works other than Andersen's but I assume they are the same. Andersen's glass is made so that the amount of solar energy that it absorbs depends on the angle of the sun. In the winter months the sun is at a lower angle, so the rays are supposed to be able to enter the home, giving some solar heat. In the summer the sun is higher, so the solar radiation bounces off the ground first and hits the window at a lower angle. The glass is supposed to be able to reflect more of this solar radiation when it bounces off the ground. In addition the low energy windows have double panes that are filled with Argon gas. 20 year warranty against seal failures . . . I'm just sayin' . . .