Home remodeling: Getting a clear view on how to lower your utility bills

Q: We need to replace the windows installed when our house was built 21 years ago because nearly half of them have a dirty haze between the double panes caused by broken seals, the air conditioner can't keep up on really hot days, and our PG&E bills have been outrageous.

Our neighbors installed tinted windows in their family room a couple of years ago when they got a big-screen TV and it really stays cool in there, but we've put off getting the same kind of windows because we don't want our rooms to be so dark. Is there any other kind of windows that will help keep our house cooler without blocking out so much light?

-- Jim Christianson, Loomis

A: It sounds like your neighbors have windows made of tinted low-E2 glass, which until lately blocked more heat than any other windows, says Steve Kuhlke, president of Vinyl Designs Inc. in Sacramento. They also prevent glare so they can be ideal for TV rooms but, as you have seen, they block about two-thirds of the light.

"It's lucky you waited because the window industry has just released a new generation of low-emissivity (low-E) glass that keeps out as much heat as solar glass but lets in 25 percent more light," Kuhlke says. "That means you can now get windows that keep you as cool as your neighbors without feeling like your house is wearing sunglasses."

Having spent nearly three decades in the replacement- window business, Kuhlke is familiar with the technological advancements in the window industry.

"First we had single-pane glass; then they started making dual pane windows to duplicate the benefits of installing storm windows during the winter in colder climates," he says.

"Although the dead air space between two panes of plain clear glass helps keep heated air inside a home longer, clear dual panes do little or nothing to keep heat out in the summer."

To address that issue, window manufacturers added tints and heat mirrors to plain glass to reflect heat. This made rooms darker, so people believed they felt cooler, but it didn't reduce inside temperatures by much, he says.

The first generation of low-E glass, made by applying a hard coating on single-pane glass that blocked ultraviolet light from the sun, was actually developed by Ford Motor Co. after auto manufacturers started replacing metal dashboards with vinyl.

"Remember how the first vinyl dashboards used to crack and buckle and the upholstery in the back windows would fade?" Kuhlke asked. "Regular Low-E glass helps prevent fading and deterioration from the sun, but it does nothing to stop solar heat gain."

The second generation of low-E glass, introduced about 15 years ago, was made by coating the inside of dual-pane windows with multiple layers of silver and metal oxides to reflect radiant infrared energy in addition to blocking UV rays. low-E2 glass windows reflect 75 percent of the sun's heat in the summer and keep heated air inside longer than clear dual panes in the winter.

"Low-E2 glass windows have been proven to save money both initially and over the long term with the use of smaller air-conditioning units to maintain proper temperatures," says James E. Swearingen of Amerimax Building Products in Woodland.

Cardinal Glass Industries, the supplier of glass used to make Amerimax windows, conducted a study comparing their "LoE2" glass to clear glass, dual-pane windows in identical tract houses in three parts of the country, including Roseville. The study showed that the "LoE2" glass cut solar heat gain by more than 50 percent and measured a 27 percent savings on cooling costs and a 10 percent savings on the heating bill.

"Tests have shown that their new low-E3 glass (called LoE3-366) reduces heat gain by 64 percent to lower equipment and operating costs even more," Swearingen says. "In California, for example, a 2,000-square-foot house with clear glass, dual-pane windows would need a 4 1/4-ton air conditioning unit, while the same house with 'LoE2'glass windows could stay as cool with a 3-ton unit and only a 2 1/2-ton unit with their 'LoE3-366' windows."