The Weitz Company is one of the oldest contractors in America – it was founded in 1855 – and the Iowa-based company is also one of the largest. In 2007, it garnered $352 million in revenue from green building projects, making it the 17th largest in the U.S. And that was officially before it entered the green market. One of its current projects is the Noyce Center at Grinnell College. It's named for Robert Noyce, the Intel founder and Grinnell alum that got temporarily booted from the school for stealing a pig.

Thus, what Weitz likes is probably a good indicator of what might find favor in the market as more builders go green and LEED.

So what is it installing? Solar hot water heaters. The payback can be as short as two to three years, says Aaron Bilyeu,   PV panels, by contrast, can take 12 to 15 years in some states to achieve payback. (Bilyeu spoke at a webinar we held earlier in the day.)

"We are reccommending [solar hot water] on all of our projects," he said. Additionally, Weitz is big on ground source heat pumps and low flow toilets.

The company has also mined gains in trying to reduce trash and waste on projects by recycling and reusing materials. On some projects, waste is down 75 percent or more, which reduces dumpster fees. During the building of a new headquarters for the Gallup organization, it actually garnered revenue from selling recycled construction materials.