Which glass should you choose for a very sunny window?

For a highly exposed opening, we look at glass that limits some solar gain (SHGC) while keeping good light. A Solarban film, for example, reflects more sun: the house heats less in summer. In winter, that “free” solar gain is a bit reduced — so choose by orientation, not a single rule.

Also worth considering

Solar shades, overhangs and trees help. You do not need the highest-performing glass if other shading exists. Low-E and Solarban are discussed opening by opening.