At Dallas/Fort Worth Airport, the lights are controlled by sensors that measure sunlight. They dim immediately when it’s sunny and brighten when a passing cloud blocks the sun.

At a new middle school in Washington, D.C., the air conditioner shuts off when a window is open.

A wall of windows at a University of Pennsylvania engineering building has built-in blinds adjusted by a computer program that tracks the sun’s path.

Buildings are getting smarter – and the next generation of building materials is expected to do even more.

Windows could trap the sun’s energy to heat hot water. Sensors that measure the carbon dioxide exhaled by people in a room could determine whether the air conditioning needs to be turned up.

“More potential products have been invented in the last 15 years than in the entire prior history of architecture,” says Philadelphia architect Stephen Kieran. “We’re only beginning to tap the potential of those materials.”

The new materials and technology are being used in a wave of buildings designed to save as much energy as possible. They range from old ideas, such as “green roofs,” where a layer of plants on a roof helps the building retain heat in winter and stay cool in summer, and new ideas, such as special coating for windows that lets light in but keeps heat out.

Most commercial buildings in the United States still lack the most rudimentary technology, such as timers for lights, but the idea of buildings that use technology to save energy got a boost from the 2000 energy crisis, when California experienced blackouts and electricity prices rose.

That year, the U.S. Green Building Council launched a program to accredit building professionals in environmental design. Interest in the program, called LEED, for Leadership in Energy and Environmental Design, has skyrocketed. Since 2000, about 19,000 people have been accredited, 9,000 in the last month alone.

About 4 percent of new commercial construction is now completed under LEED guidelines, said Taryn Holowka, a spokeswoman for the Green Building Council.

Many new building materials are first developed in Europe, where energy is more expensive. “The construction industry is behind the times in some ways, compared to many other industries,” said Patrick Mays, chief information officer of architecture firm NBBJ.

Smart building technology in the United States was formerly reserved for large projects and college campuses.

“Now we’re seeing it make its way down, even to the residential market,” said Jim Jones, an architecture professor at Virginia Tech. Think of the motion-sensing lights common outside garages and front doors.

As technologies such as sensors becomes cheaper, their uses spread.

The elevators at Seven World Trade Center, which is under construction at New York’s ground zero, a dispatch system that groups people traveling to nearby floors into the same elevator, thereby saving elevator stops and trips. People who work in the building will enter it by swiping ID cards that will tell the elevators their floor; readouts will then tell them which elevator to use.

The building also has windows with a coating that blocks heat while letting in light.

More sophisticated building materials are in development. Architect Stephen Kieran’s firm is working on “smart wrap” that uses tiny solar collectors to trap the sun’s energy and transmitters the width of a human hair to move it.

“The materials in smart wrap are either commercially available or they’ve been developed in corporate or university research labs,” said Kieran, a partner at Kieran Timberlake in Philadelphia. “They’re poised to change the face of the construction industry in the next decade or so.”

Still, relatively cheap energy costs in the United States mean most building owners remain unconcerned with efficiency, said Srinivas Katipamula, a research engineer at Pacific Northwest National Laboratory. Of the roughly 4.7 million commercial buildings in the United States, only 10 percent have energy management systems or time clocks that turn lights on or off based on the time of day, he said.