BOULDER - All new commercial buildings would require a 30 percent improvement in energy efficiency under the latest commercial green building code proposed by the city of Boulder.

The 30 percent energy improvements would be based off the most up-to-date International Energy Conservation Code, currently 2006. The city also would require energy modeling (a more in-depth type of energy audit) for all new commercial buildings more than 20,000 square feet.

The requirements likely would go into effect for any new commercial building or addition permitted in 2009 and beyond. City officials outlined goals to develop a commercial building sustainability program in 2010, require a 50 percent improvement in efficiency by 2012, require renewable energy components by 2015, and be carbon neutral by 2030. The city also is considering ways to legislate energy efficiency improvements in existing commercial buildings.

Boulder Assistant Building Official Kirk Moors presented the city's latest proposals during a public meeting on Aug. 20. Another public meeting is scheduled for Sept. 3, from 3 p.m. to 5 p.m. in the West Senior Center at 909 Arapahoe Ave.

Some developers have expressed concerns with the city trying to legislate green building. They have encouraged the city to take more of an incentive-based approach and allow the market to dictate demand. Many of the newer developments in Boulder have voluntarily been built green.

Ellen Franconi with Boulder-based Architectural Energy Corp. said she is working with the city to determine the feasibility for commercial developers to abide by the new requirements.

She said a study of recent new commercial buildings in Boulder showed that on average, developers have voluntarily improved the energy efficiency of the buildings by about 15 percent.

"So to get to that 30 percent, it wouldn't take much out of the ordinary," Franconi said. She estimated that it could cost developers 2 to 5 percent more in building costs to achieve the additional 15 percent in energy efficiency and meet the requirements.

Ways to reach those requirements could include using evaporative cooling systems and more energy-efficient mechanical systems, Franconi said. Builders could also increase day lighting and decrease artificial lighting.

"Although I understand it means a change for developers, I don't think it changes the business model much," Franconi said. "It leads them down a path to greater energy efficiency, which is a more secure place to be."

The Boulder Green Building Guild is partnering with the Boulder Chamber of Commerce to hold monthly brown-bag lunch presentations on how commercial developers can improve the suitability and efficiency in their buildings.

The first commercial green building meeting will be on Wednesday, Sept. 3, from 11:30 to 1:30 pm. in the Boulder REI's community room at 1789 28th St. BGBG also will hold a roundtable discussion of the proposed green commercial building codes Oct. 7, from 5:30 to 7:30 pm at Old Chicago in Boulder.

Contact David Clucas at 303-440-4950 or dclucas@bcbr.com.