"In San Francisco grants have been available for some time, and recently the city passed an ordinance requiring any new building greater than 250,000 square feet (within the purple pipe zone) to include water recycling to supply non-potable water to address toilet/urinal flushing and irrigation demand," says Karl Wakelin, project director at Thornton Tomasetti.

The biggest hurdle is being able to assess the success of a sustainable design element against real-world performance.

"Once we fought the disappointment that a single tool, the 'killer app,' never emerged to answer all of our form and technology questions related to energy use," says Perry. He says there now are many tools that are excellent in certain, but not all, circumstances.


But Perry is optimistic that the number of digital "Jedis" grow daily in their capacity to manage this uncertainty and find (or adapt) the right tool for proving green design effectiveness.