Dimming Windows By Turn Of A Knob

March 9, 2001 -- More than 100 years ago, the dog of an English chemist was shuffling around the lab when it piddled on a tray of iodine.

The dog had also just lapped up some quinine for a sour stomach. A combination of the quinine, the animal's own sulfates and the iodine caused the liquid to suddenly darken into green crystals. Decades later, another chemist, Edwin Land, who founded Polaroid Corp., saw a reference to the incident and used the same crystals to create glasses that can block bright light.

Borrowing again from the quirky discovery, physicist and businessman Robert Saxe, of the Long Island, N.Y.-based company Research Frontiers, has developed windows that use special crystals to block or dim the sun's rays. At the turn of a knob, the windows can dim from clear to deep blue and every shade in between.

The dimmable windows consist of two panes coated with a conductor. Sandwiched between the panes in a plastic film are free-floating particles, much like the ones created by the urine of the dog. When a current is applied to the glass, the particles align perpendicular to the glass and let light in. When no current is applied, the particles assume a more random pattern and block the light, making the glass appear deep blue.

It has taken more than 35 years to refine the so-called suspended particle device or SPD windows, but Saxe and Research Frontiers President Joseph Harary say the product should be emerging in stores this year.

Better Than Blinds

"These windows are better than blinds or shades," said Saxe. "Because, unlike blinds, you can, if you want to, cut out 50 percent of the light, you don't lose your field of view. It just dims."

Saxe and Harary declined to estimate the cost of the upcoming product. But Steve Selkowitz, head of window and building technologies at the government-funded Lawrence Berkeley Lab in Berkeley, Calif., calculates the windows would run about $100 per square foot, compared to regular, quality windows that now cost about $20 per square foot.

Once the price of the windows goes down, they could offer significant savings in air conditioning bills. The U.S. Department of Energy has said that homeowners could save between $3,000 and $6,000 a year in energy costs by using dimmable windows and decreasing the need for air conditioning.

More savings could be made, says Selkowitz, if the window systems are linked up with special lighting that automatically dims when natural light is flooding into a room. And the windows, Selkowitz says, would last much longer than shades or blinds. But first, costs have to come down.

"These kinds of windows look good, but it will be hard to justify the cost until they reach levels where owners will be saving money," said Selkowitz.

Research Fronteirs' so-called Smart Window technology is in competition with at least five other companies seeking to fill what many think will be a profitable niche of the window-making industry.

Windows With A Slower Dim

Most prominent are several companies, including Gentex and Sage Electrochromics, that have developed electrochromic dimmable windows. These windows use a gel or ceramic layer that operate like batteries and dim when electricity is applied.

Sage Electrochomics President John Van Dine claims these windows consume less electricity than SPDs, offer a clearer view and, he claims, are more durable.

"With SPDs you need to apply a constant current to keep the windows clear," Van Dine points out. "But with our product you only need to apply three to five volts to change the window's color."

Saxe argues his products would be less expensive — and SPD's also take less time to dim. But Van Dine argues changing a window's hue more gradually reduces stress on the glass and ensures it lasts longer.

In tests last year, Selkowitz and his colleagues outfitted an entire test building in Oakland, Calif., with electrochromic dimmable windows and found, when clear, the windows had a slightly yellowish tint and when tinted, offered a sleek blue, high-tech look.

Adjustable Glasses?

Both SPD and electrochromic glass won't only be limited to pane glass. The material could also be placed in car windshields, sunroofs and even glasses. Now some glasses use photochromic glass that dim according the the amount of light in the environment. But photochromic glass does not have high durability and doesn't offer wearers the ability to walk outside and immediately "dim" their glasses to shades.

Selkowitz expects dimmable windows may be the first dimmable items consumers will actually be able to find at their local hardware stores later this year.

"The dimmable windows still have a way to go," he says. "But the same kind of people who wanted to be the first to have DVD players will probably be putting in these windows soon."

And it's all thanks to a dog that desperately needed a walk.