The Indianapolis real estate investment trust, which is partnering with Kane Realty on the 17-story tower CapTrust Tower at North Hills in Raleigh, wants the building to be recognized in the U.S. Green Building Council's Leadership in Energy and Environmental Design rating system.

The program promotes Earth-friendly and energy-efficient construction. Developers earn points toward certification by incorporating features such as systems that conserve water and electricity and reduce dependence on heating and air conditioning.

The tower, to be finished a year from now, would be Duke's first Triangle building to achieve LEED status as a spec project.

Sound familiar? Duke was singing a similar tune last year, with its Regency Creek I. That building, which includes a bicycle storage room with showers (to encourage workers to use cars less) and motion-detecting faucets, was aimed for LEED certification.

The bet at the time was that a LEED-certified Regency I -- although about 10 percent more expensive to build -- would attract tenants who demanded eco-friendly space. But Duke found few prospects who would be willing to pay more green to be green. So it abandoned its LEED efforts to cut costs and pick up some wiggle room to better compete with a slew of non-green spec buildings.

After all, when tenants bargain down to the penny per square foot, shaving dollars can only help.

So what's different about North Hills? The main thing: It's easier.

The site itself accounts for a big chunk of the points needed for a LEED rating, says Jeff Sheehan, a Duke senior vice president.

It gets points for being a redevelopment -- reusing and densifying tired property instead of swallowing a greenfield. And it scores for being part of an integrated mixed-use development, which promotes walking.

Proximity to public transportation also picks up a point, as does the tower's integration with parking and stormwater systems supporting other North Hills projects.

Those are traits Regency, a secluded suburban building, didn't have. Lacking them, Duke would have had to add a few expensive features to pick up points.

CapTrust may not be the first spec office building in the Triangle to go green. Others, including Hamilton Merritt's RDU Center III in Cary, may take the distinction.

But Duke's may be the greenest.

The LEED rating system is broken down into four shades of greenness. Certified is the lowest rating. Platinum is the highest, followed by gold and silver.

Duke is aiming for a silver rating, a distinction that will be helped by all the built-in points.

That's a pretty big deal.

Institutions such as universities and government agencies, which own and occupy their buildings for decades, have been able to justify the added expense of green design by long-term energy and utility savings. A 100,000-square-foot building with about $3.5 million in green features could save $8 million in utility costs over 40 years, according to a recent estimate by architecture firm SFL&A.

The new, 17,000-square-foot Research Triangle Park headquarters last week was awarded a LEED silver rating. And this week, two Duke University buildings -- one for its nursing school and another at the medical center -- picked up the same. A third at Duke, the Home Depot Smart Home, became one of only about 100 LEED Platinum buildings in the world.

But penny-pinching real estate investment trusts such as Duke Realty, which rent out their buildings, have been more cautious about entering the green arena.

They've been willing to do it for tenants who have very specific demands. Time Warner Cable, for instance, wanted a green building at Perimeter Park in Morrisville. Duke Realty obliged and will finish the building next year. Duke also is building offices in RTP for RTI International, which seeks a LEED gold rating.

Raleigh-based Highwoods Properties entered the green world because the federal government, its biggest customer, requires the space it occupies to be LEED certified.

When it comes to spec, "it is not a clear-cut business case," Sheehan says. "But at some point, you need to step up and be a leader. We felt like it's worth the gamble."

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