The value of green building construction starts is expected to exceed $12 billion in 2008 and increase to $60 billion by 2010, according to McGraw-Hill Construction Analytics'SmartMarket Trends Report for 2008. As this growth continues, concrete material manufacturers and producers are being looked to as experts on the environmental benefits of their products, from energy efficiency to climate control.
Carbon dioxide (CO2) content is becoming a standard measurement of sustainability. Determining the carbon content of concrete can be a complex task. While concrete releases relatively low levels of 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. However, the results of recent studies vary. Fortunately, there are several new resources that can help the industry stay ahead of the curve.
For a general overview of the topic, the National Ready Mixed Concrete Association (NRMCA) offers the “Concrete CO2 Fact Sheet” (Feb. 2008). This document covers all the major points, including carbon generated during cement manufacturing, embodied carbon in concrete, and how concrete's carbon emissions compares to other building materials. It is available at www.nrmca.org/GreenConcrete.
Online calculators can take the users a step further. Mithun, a Seattle-based sustainable design firm, has developed www.BuildCarbonNeutral.org, which was first reported in the November/December issue of Hanley Wood's ECO-STRUCTURE magazine. In this article, Sean Cryan, an associate principal with Mithun, describes how the tool estimates a project's carbon content.
Mithun and several partners took data from real project cost estimates on the use of wood, steel, and concrete to determine the carbon release of structural frames as a percentage of a building's total embodied carbon. Then they added estimates for the carbon storage capacity of soil, based on the site's vegetation and eco-region.
The simple online calculator estimates the metric tonnage of CO2 released during building construction activities. It requires minimal information, such as building size, stories above and below grade, structural system, eco-region, and type and amount of landscape being disturbed or installed.
Another tool was developed by the Ontario-based non-profit, Athena Institute, www.athenasmi.ca/tools/ecoCalculator. EcoCalculator allows users to enter even more details and provides a life cycle assessment of a project's greenhouse gas emissions.
These free calculators can show the potential benefits of concrete by running quick comparisons of building materials on a given project. Depending on the situation, concrete's lower carbon content is an attractive selling point for some customers and specifiers.
“The content of the concrete is definitely important,” says Sean Cryan, “but the most significant point to remember is how it is used. If concrete can be used structurally, be part of a heating and cooling system, and develop an aesthetic statement, then it can make the most sense.”