Buildings suck up most of the energy in America, so making buildings more energy efficient, or "greener," should be a no-brainer from an environmental and energy conservation standpoint.

Now a study sponsored by investment firm Good Energies says that, contrary to popular perception, green building makes economic sense as well.

The study surveyed 150 green building projects around the world to find that, on average, they cost only around 2 percent more than traditional buildings and yielded a 33 percent savings on energy use. For about half the buildings in the study, energy and water savings yielded a five-year payback on the extra costs of going green. The study fits in with comments from people interviewed by Greentech Media over the past two years, which peg the cost of integrating various some green strategies at 2 percent to 6 percent.

Good Energies hopes the new study will counter the idea that green building is too expensive. A 2007 survey from the World Business Council for Sustainable Development, for example, reported that business leaders believed green buildings would cost 17 percent more than traditional buildings.

Real estate professionals actually are largely already ahead of the myth. Leadership in Energy and Environmental Design (LEED)-certified buildings account for a growing portion of revenue for commercial builders like Webcor. These buildings also command higher property valuations, rents and occupancy rates, industry observers said at a conference in May (see Green Buildings: No Subsidies Needed?).

Larry Vertal, senior strategist at AMD and the person who runs its sustainability programs, says it also helps with employee recruiting.

"It is one of the soft things that many companies don't understand but it is crucial in the retention and moral of employees," he said. "It is amazing how the highest talented people will grill you about your sustainability practices in job interviews."

Good Energies has a stake in promoting green building. Along with investments insolarand wind power, it has put stakes in three green building companies – Ice Energy, Microstaq and SAGE Electrochromics.

Windsor, Colo.-based Ice Energy promises technology to turn power generated at night, when it is less needed, into ice that can be used to cool buildings during the day. Austin, Texas-based Microstaq makes electronic refrigerant expansion control technology that it says can save power in heating and air conditioning systems, and SAGE Electrochromics makes glass with tinting that can grow darker or lighter to capture or reflect the sun's rays.

Running buildings – i.e., keeping lights on and running HVAC systems – consumes around 39 percent of the energy consumed in America, according to an oft-quoted DOE study, and another 12 percent is gobbled up in construction and making building products. Put them together and over half of the energy in the U.S. revolves around structures.

Other green building companies have received funding of late. Hycrete, which makes waterproof concrete, in July landed $15 million in a Series C investment round led by Mohr Davidow Ventures and including RockPort Capital Partners and NGEN Partners, according to Private Equity HUB. (See Next Cleantech Hub: India?). Gary Winnick – a mega-investor who founded now-infamous telecom company Global Crossing –has iCrete, which has devised algorithms for site-specific green cement.

Navitas Capital, a firm specializing in green building, has launched a green building investment fund that has put money into Los Altos, Calif.-based Integrity Block, which makes building blocks from rammed earth instead of cement (see Green Building VC Mystery Solved).

And Tom Siebel, founder of Siebel Systems, is putting together a contest with $20 million in prizes for companies that can build affordable, zero-energy homes (see Software Billionaire Assembling $20M Green Building Contest).

Companies in the green building field include Cal-Star Cement, which makes cement that requires less fossil fuel in manufacturing, Serious Materials, which offers less fossil-fuel intensive drywall, homebuilders Michelle Kaufmann Design and Zeta Communities, and water-heater maker American Hometec