Although many environmental impacts are associated with buildings and addressed by rating systems such as LEED, climate change deserves special consideration because buildings and land-use are responsible for a large proportion of greenhouse gas emissions. To be effective, the policies that are emerging at the local, state, and federal levels to regulate greenhouse gas emissions must reflect a clear understanding of the connection between climate change and the built environment. Unfortunately, it is not enough for green building to lessen the effects that humans have on our climate. It must also prepare us for the inevitable consequences of climate change on our homes, communities, and society as a whole. A lower-carbon future will not only have higher-performing buildings but also require higher-performing communities.
The built environment, including buildings and transportation systems, accounts for more than two-thirds of all greenhouse gas emissions. Greenhouse gas emissions come from many components of the built environment, including building systems and energy use, transportation, water use and treatment, land-cover change, materials, and construction. By improving the efficiency of buildings and communities, we can significantly reduce greenhouse gas emissions.
However, focusing on building design and construction alone will not achieve the emissions reduction that scientists believe is required to mitigate climate change. Building location is equally important. For example, a typical code-compliant 135,000-square-foot office building in a car-oriented suburban location will be responsible for approximately 8,375 tons (T) of carbon, or 11.8 T per person. Because this building is in the suburbs, emissions from transportation—people driving to and from work—make up half the total emissions associated with the project.
When that same building is moved to a location that is accessible via public transportation, bicycling, or walking, its total emissions decrease. The emissions from transportation are much less, and the relative amount from the building systems increases.
When the building is designed and maintained as a green building with improved energy and water performance, the total emissions fall to 3,233 T, or 4.6 T per person. This example demonstrates the important link between buildings and land use and the need to address both to achieve meaningful reductions in greenhouse gas emissions.
Carbon emissions provide a useful metric for many aspects of green buildings and communities, including energy, water, solid waste, materials, and transportation, but green building involves more than reducing greenhouse gas emissions. It is important to set goals for other issues as well, such as indoor air quality, human health, and habitat protection. This comprehensive goal-setting process encourages programs and policies that will lead to sustainable communities.
Flexibility and adaptability are increasingly important attributes of green projects. Although the long-term effects of climate change are uncertain, we know that sea levels will be higher, temperatures higher, droughts longer and more widespread, and flooding more intense. How different regions will experience these changes will vary considerably, and building professionals will have to assess the likely threats to their communities and respond accordingly.Download our guide, An Introduction to LEED and Green Building, to learn more