For those of us working to make green building common practice, here is our challenge and our opportunity - reduce greenhouse gas emissions, or GHG.

The commercial and residential sectors of Boulder County are the greatest producers of these emissions - contributing 31 percent and 25 percent respectively - of total countywide emissions in 2005. In the city of Boulder, 30 percent of GHG emissions are attributed to the commercial sector and 17 percent to the residential sector.

To put this challenge in perspective, a 2006 Greenhouse Gas Inventory of Boulder County demonstrates that based on a "Business as Usual" scenario (we do nothing), the county would be responsible for significantly more carbon dioxide (85 percent more tons) than the city and county of Kyoto's goal to reduce emissions to 7 percent below 1990 levels by 2012.

The good news is that the updated residential green building codes recently enacted by the city of Boulder have the most rigid energy efficiency standards in the country (www.bouldergreenpoints.com). Boulder County is adopting even more stringent energy efficiency requirements (www.co.boulder.co.us/lu/buildsmart/index.htm).

Both programs increase energy efficiency requirements as the size of the house gets larger.Education is a critical component to the implementation of these updated and new building codes. We must ensure that greening practices are done well, with careful attention to detail and a solid understanding of how to apply building science and energy efficiency strategies. The consequences of neglecting to do so could lead to unsafe environments due to poor indoor air quality and water vapor issues.

To support the transition the city is providing free workshops to help the building community meet these new codes. In addition, new construction projects must now include Home Energy Rating System, or HERS, raters.

These professionals have a strong building-science background and can identify strategies to improve energy efficiency and improve air-quality issues. Indoor air-quality concerns are also addressed in the HERS score itself (if a home is built tightly mechanical ventilation is required) and through optional green points, which is the list of "greening options" builders must choose from in order to receive a permit.

The city and county could also explore a long-term partnership with a nonprofit like the Boulder Green Building Guild, www.bgbg.org, to support the ongoing educational needs of building professionals specifically geared to support the successful implementation of the city's Green Points and county's BuildSmart.

This one-stop-shop might include cutting-edge information on building science, energy efficiency, air-quality strategies, general information on sustainable building practices, and a forum for professionals to share their lessons learned in the field. The development of a certification program would also help the public and other building professionals identify contractors with the necessary skill sets.

The jurisdictions face additional challenges to achieving significant carbon reductions in the residential sector that should be addressed through a combination of incentives and legislation.

- A large majority of the city's land - currently zoned as residential - has been developed, meaning that the HERS ratings applies to only a fraction of the housing stock (there are only about 100 new houses permitted a year compared to 51,000 existing homes.) Remodels and additions are only required to have an energy audit, not implement the recommended energy saving strategies. Energy efficiency measures, other than the efficient lighting requirement, are options on the green points checklist but not mandated. One strategy is to require that additions cannot add to an existing home's carbon footprint, and a simple remodel must meet minimal energy efficiency standards.

- Fifty-five percent of the residential sector in the city, and 34 percent in the county, is multifamily housing, yet only new multifamily housing (in the city) is required to comply with the new code. This is another sector for policymakers to address, perhaps by applying HERS ratings to remodels and offering more incentives through the city's ClimateSmart program.

- The rental market is close to 50 percent of housing in the city of Boulder. Rental property owners rarely are inspired to improve their building's energy efficiency when they don't pay the utility bill. Other cities such as Madison, Berkley, San Francisco and Burlington have all addressed this issue successfully through ordinances that set energy efficiency standards for rental units.

The city and county should fully embrace the challenge of carbon-related emissions from our commercial building stock, responsible for the largest share of our carbon dioxide emissions. Both local governments are researching how to develop building codes that address new and existing commercial buildings.

It is important to keep in mind that green building strategies, if done properly, offer several more exciting benefits in addition to lowering carbon emissions healthier environments, higher worker productivity and more dollars available to circulate in a community.

The momentum, the knowledge and the time for greening our buildings and our lives is here.

Julie Herman is executive director of the Boulder Green Building Guild. Visitwww.bgbg.org, e-mail info@bgbg.org or call 303-926-2684.