"All windows have to strike a balance between heat and light," says Jim Weisman, president and co-owner of highly rated Republic West Inc. of Scottsdale.

"As soon as you cut a hole in the wall and let light in, you let heat in," Weisman says. "To keep out heat, you have to keep out light. Exterior films are very similar to a car tint. They primarily keep some of the visible light out, which keeps some of the heat out. It isn't very effective."

Low-E glass uses layers of silver as a coating to block out heat, which Weisman says is quite effective. However, a southwest-facing window in a hot environment really calls for a combination solution. He recommends one of the four kinds of PROtec Glass Republic West offers, all of which qualify for the energy efficiency tax credit.

"One of the best ways to keep out heat is to suspend silver metallized film between two panes of glass," he says. "When you combine that with low-E glass, you get a very high heat resistance."

Weisman says consumers should also be aware that not all homes call for a one-size-fits-all approach.

"What you have on the south side of the house has completely different needs than the north side of the house," he says. "People should look at each room individually and not look for one solution for the entire house.

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