The American Institute of Architects (AIA) yesterday awarded one of its highest honors to the Philadelphia design firm KieranTimberlake Associates, cementing its reputation among the country's most innovative and influential practitioners.

KieranTimberlake, which just completed the Suzanne Roberts Theatre on South Broad Street, was given the association's annual "Firm Award" for its recent work, which blends a near-religious passion for environmental sustainability and a geeky interest in technology with elegant good looks.

In the last year alone, the firm has received national media attention for its Loblolly House on the Chesapeake Bay, the Sidwell Friends Middle School in Washington, and a prototype design for a New Orleans cottage commissioned by Brad Pitt.

For partner James Timberlake, the national AIA award comes as something of a vindication for the firm, which models itself as a research-and-development lab. "A lot of people look at us and see techies," he said. "They don't see the beauty of what we make. This award is huge."

Timberlake founded the firm with partner Stephen Kieran in 1984, after working together for several years at Venturi Scott Brown Associates, one of three other Philadelphia firms to win the prestigious AIA award since its inception 45 years ago.

From the start, the pair were keenly interested in developing methods and materials that would enable them to create buildings as modern in function as in appearance.

They began to garner national attention in 1993, with a classroom building for the Shipley School in Bryn Mawr that showed an early focus on environmentally friendly technology. For their new Sidwell Friends Middle School, they created an artificial wetland around the building to recycle its water and serve as a living classroom.

Because the construction industry is considered a major environmental bad guy, the AIA has made sustainability a major theme. In nominating KieranTimberlake for the award, Boston architect Hubert Murray wrote that "the firm has set a standard nationally that reminds us all of the fragility of the world."

Unlike some green-minded architects, KieranTimberlake generally eschews overtly earthy materials, such as corn husks and hay bales, in favor of sleek high-tech surfaces. Its architects love nothing more than to combine the latest finishes with passive ventilation and heat pumps.

As part of its interest in sustainability, the firm's architectural-research lab, housed in a cavernous loft at 20th and Callowhill Streets, has also tried to find less wasteful construction methods.

The Loblolly House project was an experiment to see whether the architects could use computers to create a building that could be assembled on-site like an Ikea bookcase, from flat panels embedded with wires and pipes.

Kieran boasts that the method reduced the waste they produced from the industry average of 40 percent to just 7 percent.