The GBI claims to be fairer to the builder, since it had extensive industry involvement during development of its guidelines, including from the concrete and masonry industries. Its Web site states that “the GBI believes in building approaches that are environmentally progressive, but also practical and affordable for builders to implement.” An extensive set of guidelines, the NAHB Model Green Home Building Guidelines, are available free at www.nahbrc.org/green guidelines/community.html. NAHB's National Green Building Conference is scheduled for March 25–27, 2007 in St. Louis.
Although LEED and Green Globes award points for many other things, energy efficiency remains a major objective of green construction. The oldest standard for energy efficiency is the Energy Star program from the U.S. Environmental Protection Agency and the U.S. Department of Energy. Although most recognized as a sticker on appliances, Energy Star also has standards for home construction and rehabilitation, and it is a checklist item in LEED.
The initial set time and 28-day cylinder strength for these three different mixes using high volumes of fly ash (51% replacement of cement) show that proper proportioning can overcome any negatives.
Another method for measuring energy efficiency is the RESNET Standards—the Mortgage Industry National Home Energy Rating Systems Standard—developed by the Residential Energy Services Network (www.resnet.us). This standard provides an extensive and detailed method for measuring a home's energy efficiency, resulting in a HERS rating (Home Energy Rating System)—a number that indicates how energy efficient a home is relative to a standard reference house. The complete detailed standard is available free from RESNET.CONCRETE'S ROLE
In the November 2005 issue of RESIDENTIAL CONCRETE, David Shepherd, director of sustainable development for PCA, wrote an article that included a listing of how concrete contributes to green home construction. To review this article, go to www.residentialconcrete.com/buildinggreen. Concrete homes by their very nature add to sustainability by producing durable, airtight walls. Trombe walls are making a comeback and rely heavily on concrete see Trombe Walls. Another feature you are very likely to see is the inclusion of fly ash or ground granulated blast furnace slag (GGBFS or slag cement) in a concrete mix. Both LEED and Green Globes award points for the use of recycled materials. These pozzolans improve concrete properties, but beware of slow set times and slow strength gain.
Construction using insulating concrete forms (ICFs) is another method that contributes to a home's sustainability points. A recently completed ICF home on the Mississippi River near Hardin, Ill., gained an Energy Star rating and qualified for a $2000 tax credit. “I did an energy rating on this house,” said Allan Anderson, who is certified with the Illinois Association of Energy Raters—a certified provider through RESNET. “The house was built by the owners of Hardin Ready Mix for their own use and has Eco-Block walls with EIFS on the exterior. It gained the Energy Star rating by being 50% more energy efficient than the reference home.”
Green construction is something every contractor in the United States has or will soon encounter. Those who can speak knowledgeably about it and who embrace it will acquire this profitable work.Concrete's Sustainability Solutions
The following are “environmental challenges or issues” that concrete can help mitigate. Go to www.concretethinker.org to learn more about each:AcousticsBuilding reuseDisaster resistanceDurabilityEnergy performanceHeat island reductionIndoor air qualityLEEDLife cycle balanceLighting efficiencyLocally producedMinimize site disruptionRecyclableRecycled contentResource efficientSite remediationStewardshipStormwater managementThermal mass