post from Kelly McGinnis of the Portland Cement Association. As PCA’s Program Coordinator of Sustainable Development Ms. McGinnis is responsible for several green outreach and education programs for the design and construction community. Additionally, she oversees content development for www.ConcreteThinker.com and its companion sustainably-focused e-newsletter.
Ms. McGinnis is a member of the Chicago Chapter USGBC and serves on its Education and Research Committee. She has more than 6 years experience in the environmental sciences and has a Bachelors degree in Environmental Science and Ecology from Evergreen State College, Olympia, Wash.
Follow the Portland Cement Association on Twitter @concretethinker.
The cement industry is aware of the environmental impacts of cement manufacturing and continues to work toward reducing those impacts. Because of environmental concerns, some dismiss cement products as sustainable building materials. These naysayers, however, are missing the ability of concrete building systems to actually negate the initial impact of cement manufacturing through concrete’s incredible durability and the long-term energy efficiency it provides.
Compare a home built with insulated concrete forms (ICFs) and to the same house built with typical wood frame. The ICF home will use less energy over its life span, including the initial energy used to manufacture the cement and concrete. Less than 0.5% of the total life cycle energy in home construction is due to the embodied energy from the manufacturing of cement and production of concrete. In a typical household, 85% to 95% of the total life cycle energy is due to heating and cooling. The remaining 5% to 15% comes from embodied energy from all incorporated materials, and the resources expended during the initial construction, on going maintenance, and then final demolition of the home. Because of its more efficient performance, about 5 to 7 years, the total energy used to produce and operate an ICF house will become less than the energy used to produce and operate a wood frame house. During a 100 year life span total energy savings translates into at least 220,460 lbs less CO₂ emitted by the cement based product home.
By taking a step back and looking at concrete through its life cycle, like in this example, the impact of the manufacturing of cement is quite small compared to other factors. But that is just the beginning of the tradeoff story. Buildings should be built to last generations. Concrete structures have withstood the tests of time. Concrete doesn’t rust, rot, or burn. It can withstand natural disasters like hurricanes and tornado’s. When used for buildings and pavements the result is a long-lasting infrastructure that requires minimal maintenance. These many benefits make concrete a practical solution for environmentally responsible design.
Other concrete construction properties play into the equation as well. Concrete is able to absorb radiant heat from the sun and then gradually release that heat during the night. This causes shifts in peak energy load. Additionally, heat transferring through the concrete walls outside is reduced because of concrete’s inherent thermal mass, therefore requiring less energy to heat and cool the inside of the building. In the US about 40% of our CO₂ generated comes from the operation of buildings, mainly the heating and cooling.
Understanding this puts into perspective the real value of applying durable, energy efficient structures and envelopes like is possible with concrete. Consider the design of lighting controls for optimized lighting performance. Significant savings can be achieved. Now imagine a design process where the structural and mechanical engineers work in concert, integrating the structure, envelope and H VAC system; storing energy in the mass, tightening exterior losses and reducing space and loads to support smaller H VAC equipment and ductwork.
The sustainable design community has yet to find a “perfect” building material; everything has good features that are weighed with less than desirable ones. A full life-cycle analysis illustrates the benefits of using optimal amounts of insulation, thermal mass, orientation, and other energy saving features and demonstrates the long-term environmental benefits concrete provides.