The University announced the future site and architect of the first building for its new campus in Allston Friday, a move that revives a planning process that has made little progress since last May.

The 500,000 square foot science complex, which will house the Harvard Stem Cell Institute, will be located on the south side of Western Avenue adjacent to the WGBH radio station. It will be designed by Behnisch, Behnisch & Partner, a German firm renowned for its environmentally-friendly modern designs.

In an interview Friday, Professor in Practice of Urban Design Alex Krieger, whose company, Chan Krieger & Associates, is helping design open spaces in the Allston campus, said the decision is the first concrete step taken since planners released a report last May outlining possible sites for several Harvard buildings in Allston.

The Western Avenue site ultimately chosen has been under consideration since planning began.

“The planning team has been sitting on their hands for most of a year now,” Krieger said. “It’s very significant because it seems to be so difficult for the president and the provost to reach a consensus [with the University community].”

Provost Steven E. Hyman said in a conference call on Friday that the University hopes to complete the design and permit process within the next 18 months. Construction is set to begin by 2007.

“We may be able to get in the door within two years,” said Christopher M. Gordon, Harvard’s chief operating officer for Allston development.

Behnisch, Behnisch & Partner was selected from a pool of 40 initial applicants by a 12-member “architectural jury,” which included Paul Goldberger, the New Yorker’s architecture critic.

Gordon said the architects had not yet defined the style of the new building, but almost all of the firm’s prior work, including Genzyme’s glass headquarters in Kendall Square, eschews traditional design.

Krieger called the choice “slightly courageous” and “slightly controversial.”

“I don’t think they’re going to do anything particularly wild but they’re not going to necessarily reproduce the iconography of the Cambridge campus,” he said.

Hyman said the Harvard Stem Cell Institute needed its own space because federal restrictions on stem cell research make it difficult for scientists who study stem cells to share lab space with federally-funded researchers.

“It’s led to situations where a graduate student in the middle of an experiment can’t use a particular piece of equipment,” Hyman said.

Harvard also confirmed Friday that it would temporarily locate some of the Harvard University Art Museums collections in the former Citizens Bank building on Soldiers Field Road, while the Fogg Art Museum undergoes renovations.

Though University representatives met with Allston residents last Monday, they did not name the architect or the location of the building.

Gordon said the University had waited to coordinate the news with Boston Mayor Thomas M. Menino’s office.

Menino made the first public announcement of the plans at a speech to the Boston Municipal Research Bureau on Friday, touting the potential of Harvard’s expansion to increase jobs in the region.

University planners have estimated that the science complex could add 1,000 jobs to the area.

Neighbors also greeted the news with optimism, suggesting that Harvard’s efforts to get the Allston community on board its scientific agenda have proved fruitful.

“It seems that bio-science is one of the industries that Boston wants to compete in and it seems like a terrific advantage that we have somebody with deep pockets and the intellectual resources to do it,” said Harvard-Allston Task Force chair Ray Mellone. “It captured the imagination a bit.”

The 17-member Task Force, composed of Allston residents appointed by Menino, is charged with reviewing Harvard’s expansion plans as they are presented to the City.

Before the University can proceed with construction, it must submit an Institutional Master Plan to both the City and the Task Force.

“There is a process by which all of these ideas have to be processed and looked at,” Mellone said. “Harvard has to produce formal documents in order to start that up.”

—Staff writer Natalie I. Sherman can be reached at nsherman@fas.harvard.edu.