Almost clear way to block out the sun

DARKENED windows aren't only for starlets shunning paparazzi or for low riders.

Blocking out the sun's rays can help prevent your car from turning into a kiln in August, reducing the need to run a power-sapping air-conditioner at full tilt.

So what if you want the benefits of shading the sunlight but don't want to look like part of a Britney Spears motorcade?

One maker of sun-blocking window films, Solar Gard, says it has a solution: a nearly clear window treatment that helps to beat the heat by limiting the amount of infrared radiation that enters the car.

Typically, keeping the sun out required choosing between dark window films, which can impair visibility, or metallic treatments. Neither is a perfect answer: dyed coatings reduce glare but can fade over time, and they may develop bubbles. Metallized films, on the other hand, tend to be more reflective and can interfere with radio frequency signals used by cellphones, tyre pressure monitors and radio antennas embedded in the window glass.

"That's why we don't carry anything metallic anymore, so its pretty much obsolete," said Ryan Baxter, an installer with Pro Tint, a glass treatment shop in Salt Lake City.

Solar Gard, based in San Diego, has been working for several years to perfect a film coating of nanoparticles designed to limit the infrared portion of sunlight that enters the car.

The company says that its Ultra Performance window films will do the job while allowing 76 per cent of visible light through; with additional layers it can also block out 99 per cent of ultraviolet radiation.

Baxter said that installation costs from US$260 to US$290 per car, about US$60 more than traditional treatments.NYT