The value of green building construction will exceed $12 billion Tin 2008 and may increase to $60 billion by 2010, according to McGraw-Hill Construction. As this trend continues, some look to concrete producers as experts on the environmental benefits of their products, from energy efficiency to climate control.
Carbon dioxide (CO2) content is also becoming a standard measurement of sustainability. Determining the carbon content of concrete can be a complex task. While the material releases relatively little CO2, the cement manufacturing process does produce a certain amount.
Concrete's carbon content seems to stand up well against other materials such as wood and steel. But the results of recent studies vary. Fortunately, there are several new resources that can help producers in this area.
For an overview, the National Ready Mixed Concrete Association offers the “Concrete CO2 Fact Sheet” (Feb. 2008). This document covers all of the major points, including carbon generated during cement manufacturing, embodied carbon in concrete, and how concrete's carbon emissions compare to other building materials. You an find it at www.nrmca.org/greenconcrete.
Online calculators can take producers a step further. Mithun, a Seattle-based sustainable design firm, has developed www.BuildCarbonNeutral.org, as first reported in the November/ December issue of ECO-STRUCTURE, THE CONCRETE PRODUCER's sister magazine. In this article, Sean Cryan, an associate principal with Mithun, describes how the firm developed the tool and how it estimates a project's carbon content.
After realizing there was no simple tool to measure the carbon embodied or released during construction of a building, Mithun worked with several partners to create a Web-based solution. The team took data from real project cost estimates on using wood, steel, and concrete to determine the carbon release of structural frames as a percentage of the total embodied carbon of a building's shell and core.
This database produced estimates of average CO2 emissions per square foot of construction using the different building materials. With the addition of estimates for the carbon storage capacity of soil, based on the site's vegetation and eco-region, the calculator was complete.
Available since April 2007, this online calculator estimates the metric tonnage of CO2 released during construction. It is simple and only requires minimal information, such as building size, stories above- and belowgrade, structural system, eco-region, and type and amount of landscape being disturbed or installed.
Counting greenhouse emissions
EcoCalculator, developed by the Ontario-based non-profit group, Athena Institute, is available at www.athenasmi.ca. The EcoCalculator allows users to enter more details, and it provides a life cycle assessment of a project's greenhouse gas emissions.
Builders and homeowners are already using these calculators to calculate carbon offsets of homes. Architects use them to determine the benefits of renovating buildings versus building new ones. Producers can educate themselves and their customers about potential benefits of using concrete by running quick comparisons of building materials.
Concrete's lower carbon content can be an attractive selling point for some customers and specifiers. Carbon-related policies are appearing in the construction policies of some states, such as Washington and Massachusetts. In the near future, producers may even be measuring a project's carbon footprint as they develop their Prescription to Performance (P2P) specifications.
“The content of the concrete is definitely important,” says Sean Cryan, principal with Mithun. “But most important to remember is how it is used. If concrete can be used structurally, be part of a heating and cooling system, and can make an aesthetic statement, then it can make the most sense.”