Key is the clarity of the new films, which allow in maximum light and decreases energy consumption. "We've had tenants put no lighting in perimeter offices because of that,"Gonzalez says.

Installation is taking place on the building's east, south and west sides; installation on the north side was not needed, Venet explains. The film is replaced as tenants turn over, so L&L is able to see the effects of the change. "We notice a significant heat rise in areas not yet filmed," Gonzalez says. "We find it does cool the building."

At 600 Third Ave., the installation is part of an overall upgrade that includes upgrading the controllers and increasing the landscaping. Installation at midtown building began in December will be finished by the end of this month, ahead of schedule.

L&L is not alone in looking to thin films to help curb tenant energy costs. The October 2008 Emergency Economic Stabilization Act allows tax credits for homeowners who install energy efficient improvements in 2009, with window films possibly qualifying, according to the International Window Film Association (IWFA), in Martinsville, VA. Commercial real estate, however faces greater economic challenges.

"There's a tremendous amount of interest," with the recent spikes in the price of oil, says Darrell Smith, executive director of the IWFA. "But the same people who are worried about energy bills also are worried about layoffs."

What can help is that the length of office lease terms has declined over the years, from 20 years to 12 years to seven, giving the opportunity to retrofit. Yet uncertain financing and ownership consolidation has slowed the momentum.

"Everyone is wading through the stimulus package," Smith says, speaking before the passage and marrying of the Senate and House bills. "Six years ago, one company, one manufacturer had a proprietary technology to produce a clear film, a spectrally selective film [which distinguishes the different wavelengths to block ultraviolet rays and some solar energy, while allowing visible light to penetrate]," Smith points out. "Today, almost all major manufacturers do."

In fact, the technology has advanced to the point that some films not only will block light, they also contain ultra-thin photovoltaics to allow the film to produce energy. The payback period on solar films varies by region. In the South, payback can range from six months to three years, Smith said. In the central third of the United States, the period could be from two to six years. Determining the payback period in the northern part of the country would require an energy analysis. Venet estimates that 600 Third Ave. will have a five-year payback.

The resulting energy savings can become a huge draw for tenants, Venet says. But aesthetics also are an important consideration, as people focus more on the appearance of a building's exterior. "You can restore a building to its original architectural integrity," Venet says. "At 600 Third, they're returning it to the way it was supposed to be."