Tenants seem to think so, according to RICS' quarterly survey of tenants. Full third quarter results will be released next week, but Hartenberger previewed some changes, including client demand for sustainability now outstripping legal compliance as a motivator for going green.

"There were fears a year ago that [a commitment to sustainability] would be dead," Hartenberger said. "I said it would prove to be a temporary thing."

Still, the growing chance of regulation is a concern, and one reason why green will be valuable in a lease. "Global leaders realize the urgency of this issue," Hartenberger said. "The world is changing. Buildings do have quite a role to play in reducing greenhouse gases, and it's relatively low hanging fruit."

The result is that owners should look at greening buildings before they are compelled to do so, and reap competitive advantages by being early adopters. "Governments are becoming increasingly proactive on green legislation," Recny said. The implication is simply that landlords and tenants will have to go green whether they want to or not.

Awareness is growing that they should want to. Energy represents 7% to 9% of all occupancy costs, and a number of investment funds are focusing on green buildings, said John Quigley, Professor of Economics at the University of California, Berkeley, a co-author of the RICS-sponsored study "Why Do Companies Rent Green? Real Property and Corporate Social Responsibility," undertaken by Maastricht University in The Netherlands and the University of California, Berkeley. Green buildings, as a result, have better, more stable, occupancy; higher office rents--between 6% and 9% higher; and higher selling prices--approximately 16% to 17% more. "This can be attributed to energy efficiency, but also the labeling effect," Quigley said.

Other factors are the role renting green can play in burnishing a corporate reputation, a reason why petroleum and gas companies are "far more likely to locate in green office space." One benefit does not seem to be greater productivity, Quigley said, though there could be indirect benefits.

But the downturn is having effects, said sustainability expert Paul King, former vice president of sustainability for Bovis Lend Lease. Companies are holding back on retrofitting offices "because it's not the right thing to do while you're laying people off."

President Obama has backed away from a strong US commitment to the Copenhagen Climate Change Treaty draft, which calls for a national commitment to greenhouse gas reductions. "It's sent a shock wave through the environmental community," King said. "But it will have to move forward at some point, because it hasn't gone away."

Another problem on the building front is that many technologies have extremely long paybacks, a disincentive for investment for anything other than new buildings and a major retrofit. "Some can be 20 to 50 years," King said. "You'll need other incentives to do most, and I suspect that will be regulation."

But with populations increasing, governments and companies have no choice to pursue all energy alternatives, King noted.

"[The earth's population] will be at 9 billion by 2050, and the trend is toward the western lifestyle, which is very energy-intensive," King said. "Regardless of your political beliefs, we are not in the Middle East just to spread democracy. Windmills and solar panels will exist. The world has to move in this direction."