According to David Walls, executive director of the California Building Standards Commission, the body that developed CALGreen, the code has turned out to be a milestone for sustainable building practices. “No other state or city has actually developed or adopted a green building code,” said Walls. “Some of them have adopted LEED-based programmes, but none are getting out there and mandating specific requirements like we have. A lot of people have said it’s a really big push in the right direction.”

Many hope that this “push” will spread beyond California’s borders in the years ahead. “People got comfortable with LEED and started taking it for granted,” says AbhishekLal, programme manager for Architectural Energy Corporation in Washington, DC. “CALGreen forces people to take another look, and challenges business as usual. I think CALGreen resets the goals with green building that other regions in the US are not doing.”

CALGreen could also offer a blueprint for other countries.

Internationally, some cities, such as Dubai and Singapore, have adopted compulsory codes but most regions rely on voluntary certification systems to drive green building practices: in addition to LEED, there are a wide range of available, overlapping and sometimes conflicting standards, such as the BRE Environmental Assessment Method (BREEAM) – devised in the United Kingdom in 1990 and now widely used across Europe – and Green Star in Australia.