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Feature Story - October 2007

Counting Carbon

Online Construction Carbon Calculator for Sustainable Development

Introducing a new tool for measuring the carbon output of construction projects, Mithun, Seattle, and the Lady Bird Johnson Wildflower Center have joined forces to expand current understanding of the construction industry's role in global warming and help it to reduce greenhouse gas emissions. Designers, developers, owners and contractors armed with this information can engineer the entire site - building and landscape - to reduce its carbon footprint.

The new carbon calculator, known as BuildCarbonNeutral, is available at buildcarbonneutral.org. It generates a uniquely integrated perspective for use in the first phase of design - reviewing the amount of CO2 released not during the lifetime of a completed building, but by its materials and site during the construction process.

"BuildCarbonNeutral is designed to improve with use," says Bert Gregory, FAIA, Mithun's president and CEO. "The calculator is based on our research into existing models combined with data sets culled from multiple series of construction cost estimates and ecological literature. Adding more data will increase its effectiveness. We welcome feedback to develop ideas and technology that will support growing efforts to reduce global warming."

Intentionally simple, the calculator appeals to a wide range of interests and works with information for any kind of construction or site, including urban contexts without vegetation, as well as for only a building or only a landscape. Using square foot measurements, it asks for:
 (1) a building's size, number of floors, and structural frame material;

(2) the project's eco-region, amount and type of landscape removed, and amount and type of landscape added.

According to Sean Cryan, a LEED Accredited Professional at Mithun, "We've introduced BuildCarbonNeutral as a starting place. Once you have a number, you can begin to take action. We hope that more complex forms will develop to include carbon offset recommendations in addition to carbon release measurements."

Mithun and the Wildflower Center identify three important steps to decrease the environmental impact of new construction: Reduce, renew and offset. It's a tiered strategy that concentrates efforts first on reduction of a project's embodied energy and carbon, then renewable sources of energy and renewed ecosystems, and finally on positive means to compensate for any remaining CO2.

Concerns about climate change have greatly increased interest in sustainable building design. In the United States, buildings are a major consumer of energy, producing about 48 percent of our greenhouse gas emissions, according to the Environmental and Energy Study Institute. Because most carbon calculators estimate the amount of carbon dioxide released during the day-to-day operation of buildings, designers have lacked an important tool - one that calculates the total amount of carbon dioxide produced as a direct result of the energy required to manufacture, transport, and assemble construction materials.

Existing calculators also fail to account for carbon held in landscape vegetation and soils, sometimes for hundreds of years. This first version of BuildCarbonNeutral estimates the amount of carbon dioxide sequestered or released as a result of destruction or restoration of large natural landscapes, such as prairies or forests. Future versions will expand to calculate smaller urban landscapes, such as roadsides, lawns and gardens.

Peer review is underway, conducted by two internationally recognized authorities on greenhouse gas emissions: The World Resources Institute and the University of Bath, Mechanical Engineering Department. Additional peer review will be undertaken by the Cascadia Chapter of the US Green Building Council. The University of Washington Program on the Environment also provided early research for the calculator into the carbon release impact of site excavation.

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