Building energy codes, a staple among the policies regulating construction, yield solid reductions in consumption and emissions, according to research that examined hard data on energy use in states with codes on the books.

Although energy codes have existed in the U.S. for nearly 40 years, estimates of the benefits that result from them have largely been theoretical and based on simulations.

Findings released today in a report by the Climate Policy Initiative prove that "energy codes are working, and they deliver energy savings not just in a theoretical sense -- there is solid evidence they actually do," said Kath Rowley, the director of CPI's office in San Francisco and the head of the organization's research program in North America.

Researchers looked at residential energy use from 1986 to 2008 in 43 states with building energy codes. The review found that in homes built to the codes:

• Energy consumption was 10 percent less than energy use for homes not built to the codes.
• Residents tend to shift from oil and wood fuels to natural gas, which results in fewer emissions. The change is apparently the result of code provisions that encourage high-efficiency gas units and electric heat pumps.
• Energy-related greenhouse gas emissions were lower. Research indicated that the combined effect of lower energy consumption and fuel switching resulted in ghg emissions that were on average 16 percent less than emissions from homes that were not built to codes.

CPI Senior Analyst Jeff Deason, the lead author of the report, pointed out the estimate for the average reduction in energy consumption is better than the 5 percent generally projected in simulations of energy use under such codes.

The organization's report is part of a larger CPI research project of building policy in key regions around the world. The study follows work by the Institute for Market Transformation to catalog building energy performance policy globally and provide tools for building owners and managers to navigate those regulations. The CPI study also comes after the U.S. Green Building Council's state-by-state report on gains and challenges to green building policy.

Mandatory building energy codes, green building codes for new construction and major renovations, building energy performance requirements and voluntary green building aspirational programs, such as the USGBC's Leadership in Energy and Environmental Design rating system, are considered key weapons for combatting climate change in the built environment. The aspirational programs provide the stretch goals and codes set the threshold.

As more cities and states consider green building measures with varying results, the role of long-time mechanisms such building energy codes becomes more apparent. The research from CPI offers evidence of how codes not only set the baseline for expectations, but also drive greater efficiency on a broad scale.

Image CC licensed by Flickr user Martin Pettitt.