RTI International appears to be getting greener. The fast-growing think tank, which has earmarked $100 million for a face lift and expansion at its 180-acre Research Triangle Park campus, wants an Earth-friendly building in the mix.

RTI last month told the U.S. Green Building Council that it wants a planned 122,000-square-foot building to meet the standards of the Leadership in Energy and Environmental Design, or LEED, rating system.

The council established the system in 2000 to promote energy-efficient construction.

Developers earn points by incorporating features such as systems that save water and electricity and reduce the need for heating and air conditioning.

The RTI project caps one of the greenest months yet for the Triangle. Seven projects sought LEED designations in June, bringing this year's tally to 19 -- four times the annual average over the previous six years.

Among them:

* Chapel Hill plans a green library at 100 Library Drive.

* Duke University is planning Duke Law Commons, a 110,000-square-foot green building at Science Drive and Towerview Road in Durham.

* Meredith College plans 104,000 square feet of apartments on its Raleigh campus.

Nonprofit groups and institutions such as governments and universities have been more willing to go green than developers who operate real estate as an investment. Institutions tend to keep the buildings longer and can justify a little extra upfront construction cost.

A 100,000-square-foot building without sustainable-design features might cost $30 million to operate more than 40 years, according to architecture firm SFL&A. The same building with about $3.5 million in green-design features could save the operator $8 million in utility costs over the same period, based on current energy prices.

Now many developers are boning up on green design to nab institutional clients who want sustainable buildings. They were once hesitant to incur the higher costs of eco-friendly construction, fearing they might lose out in rental-rate battles.

Durham records show that Indianapolis real estate investment trust Duke Realty will build RTI's building, which would have a data center and auditorium.

Last week, Raleigh REIT Highwoods Properties revealed its first green project: a $31.7 million, 110,000-square-foot office building in Jackson, Miss., that it plans to lease to the Federal Bureau of Investigation when it's finished in 2009.