The nation's ten largest publicly traded homebuilders have begun to improve their sustainability efforts, although they still have a long way to go, found a major study released yesterday by Calvert Asset Management Co., a leader in sustainable and responsible investing.

Out of a possible 42 points across five categories--land use, building materials, energy, water, and climate change--their average total score was just over six points or 15%. Without the study's No. 1- and No. 2-ranked homebuilders, KB Home and Pulte Homes, the average score would've dropped to less than 6%, noted Calvert.

The rankings in the new study, "A Green Recovery for America's Homebuilders? A Survey of Sustainability Practices by the Homebuilding Industry," were primarily based on publicly available data. Companies were also invited to share any other initiatives underway.

"Whereas two years ago the industry had not yet begun to embrace sustainability as a core part of building design and construction, companies today have taken many meaningful steps toward developing greener and cleaner homes," report co-author Rebecca Henson, a Calvert sustainability analyst, said during a press conference. "We now see companies beginning to treat sustainability as a strategic business issue and are therefore starting to improve their policies and practices relating to the environment."

Homes account for about 21% of all U.S. energy-related carbon dioxide emissions and about half of public water consumption, noted the report. The green building market, estimated at $36 billion to $49 billion, is expected to increase two-fold between 2009 and 2013, according to figures cited from McGraw Hill Construction's Green Outlook 2009.

"Neither the economic crisis nor the political uncertainty around climate policy have thwarted or seriously impeded the sustainability efforts of the nation's largest builders," said Henson. "We believe that green buildings represent an opportunity to the industry as it focuses on rebuilding its market and restoring and strengthening financial profitability."

The study found homebuilders are now making company-wide national sustainability commitments instead of favoring regional policies and programs. Among the five areas analyzed, energy scored highest. All 10 homebuilders have commitments or initiatives concerning energy efficiency. KB Home, No. 3-ranked Meritage Homes and No. 8-ranked NVR (through its subsidiaries), have national commitments to build all new homes to EnergyStar standards.

Still, there are big differences between homebuilders. "Overall while the industry is moving forward, on a company level that's piecemeal," noted report co-author Jennifer Green, an associate sustainability analyst with Calvert. For example, KB Home is the only large U.S. homebuilder that has produced a comprehensive sustainability report--something roughly four-fifths of the world's largest companies do, according to KPMG's International Survey of Corporate Responsibility Reporting 2008.

KB Homes is also educating consumers about energy savings, experimenting with "smog eating" roof tiles, and introducing alternatives to "McMansions." "We look forward as a company to continue to pave the way in showing that what is good for the earth and our customers is also very good for our business," said president and CEO Jeffrey Mezger.

The remaining homebuilders, by survey ranking: Toll Brothers (No. 4), Lennar (No. 5), DR Horton (No. 6), Standard Pacific (No. 7), Ryland Group (No. 9) and MDC Holdings (No. 10). "There are still opportunities for any company to become a leader in sustainable residential construction," concluded the Calvert study.