Sustainable Construction with Concrete

Whether you are completely convinced that human activity is causing global warming or think Al Gore invented it the way he did the Internet, you likely are to be involved in a project in the very near future that incorporates sustainability concepts. Sustainability is here to stay and there is no reason to shy away from such projects as long as you understand some of the basics.

Sustainable, or green, construction seems to have reached a critical mass. Governments suddenly have signed on, especially for public and commercial buildings. Tax credits are available in many states and even bankers are getting into the mix. According to USBanker magazine, “Banks like PNC Financial Services and Bank of America are at the forefront of the green-building craze.” And in Europe, the European Union has issued a directive to require new homes to have energy performance certificates—can the United States be far behind?

A Trombe wall has masonry or concrete on the inside that is painted black on the exterior face, an air space, and glass on the exterior of the home. The completed walls look like windows with black shades. Photos: Joe McGovern, Living Designs Group

Concrete can contribute to sustainable construction, according to Portland Cement Association's (PCA) Web site ConcreteThinker.com, in 19 different ways (see Concrete's Sustainability Solutions). Many of these are simply natural attributes of concrete, such as acoustics contributing to quieter rooms, durability, and thermal mass. Others require modifications to the design, materials, and construction, such as the incorporation of recycled materials or energy performance. Concrete contractors may be called on to provide many of these things.

Where did “green” come from and why suddenly are we hearing so much about it? This actually has been sneaking up on us for several years, but has gained momentum in the past few. The nation's leading sustainability organization is the United States Green Building Council (USGBC, www.usgbc.org), which was founded in 1993. In 2003 its membership was only about 2000 companies and organizations, but today its membership has skyrocketed to more than 7700, tripling in number the past three years. The USGBC sponsors Greenbuild each year, a conference on sustainable construction scheduled for Chicago, November 7–9, 2007.

Despite its official-sounding name, the USGBC is not a government agency, but rather a nonprofit association. The organization's primary focus has been its Leadership in Environmental and Energy Design (LEED) Green Building Rating System. There's a lot of misunderstanding about LEED: it is not a building code, it is not even a design system, but rather a way to measure how green is green. LEED aspires to look at the entire home and its environment, not only its energy efficiency. Points are awarded for a variety of home features, including such things as where trees are planted and how close the home is to public transportation. Points also are awarded for permeable pavements and the use of local materials (such as locally produced concrete and aggregate). To become a LEED “certified” home, the project needs to gain at least 30 points; 50 points make it a LEED silver project, 70 points gold, and 90 points platinum. In some cases, it seems that designers and builders are incorporating things into projects purely to accumulate LEED points, even if there might be better, more truly sustainable ways.

Although LEED seems to be becoming the standard, it is not the only game in town. There are other perfectly valid ways to measure the sustainability of a home's design and construction. The National Association of Home Builders (which sponsors this magazine through its Concrete Home Building Council) has developed a program they call the Green Building Initiative (GBI, www.thegbi.org). This program incorporates Green Globes, which is an online sustainability rating system similar to LEED. Green Globes originally was developed in Great Britain, then imported to Canada where it is administered by ECD Energy & Environment Ltd. NAHB has adopted Green Globes for home construction.

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.

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.

The following are “environmental challenges or issues” that concrete can help mitigate. Go to www.concretethinker.org to learn more about each: