Concrete Solutions for the NAHB National Green Building Standard™

ICC 700-2008 National Green Building Standard ™ (Standard), developed by the National Association of Homebuilders (NAHB), is a comprehensive program which provides guidance for improving the environmental performance of residential construction.  Many sustainable features of concrete homebuilding technologies can contribute to the certification of successful, well performing green homebuilding projects under this Standard.

What is ICC 700-2008 National Green Building Standard™?

Developed through a partnership of the NAHB, and the International Code Congress (ICC), the Standard is the first to be developed under the strict requirements of the American National Standards Institute (ANSI).  These requirements insure the provisions were vetted by a committee representing the broad interests and stakeholders in the green residential marketplace.  The result is a true consensus based ANSI Standard that doesn’t simply offer ways of adding expensive upgrades to conventional homebuilding systems.  Instead it allows builders to earn green building credits by using more innovative, cost effective choices like concrete for their high performance homes.

All types of non-institutional residential structures in all climates are covered by the Standard: new individual single family homes as well as multi-family projects of all sizes.  It covers renovations and additions to existing homes as well.  There are also provisions for the design of subdivisions and for individual home sites. 

Two separate scoring systems for new construction are featured in the Standard: one to cover compliance of the design of residential subdivisions (Table 1), and a second to cover the compliance of the construction of each dwelling unit and its lot (Table 2).  A subdivision can achieve a One Star through Four Star rating while individual homes can achieve certification under Bronze, Silver, Gold or Emerald Performance Levels. 

How can concrete homebuilding systems contribute points toward certification?

Highlighted below is a brief description of the various Green Building Practices from the Standard where concrete will make significant contributions.  Table 3 provides a detailed summary of the specific green building practices where concrete benefits can contribute to certification under the Standard.

Site Design and Individual Lot Design, Preparation and Development

Whole green subdivisions as well as individual lots can benefit from the use of concrete.  Cementitious systems can make selection of infill sites and/or greyfield or EPA recognized brownfield sites feasible.  The fire resistance properties of concrete can make building on an urban infill site practical and cost effective by creating more buildable lot area than is possible with combustible construction.  Through the use of portland cement for soil solidification and stabilization, previously contaminated sites in urban environments can be reclaimed and successfully redeveloped.  The cement is used as a binder to physically and often chemically neutralize hazardous substances within contaminated soils. 

Resource Efficiency:

The Standard encourages better management of materials to reduce waste, environmental impact, and to provide a more durable finished product.  Various concrete applications can help.  Use of basements to enclosed living space can reduce overall home footprint, reducing overall site disturbance, and above grade conditioned floor area.  By planning a project based on the modular dimensions and the structural efficiency of various concrete technologies, on site waste is virtually eliminated.   Any surplus concrete construction materials can be crushed and reused as pavement base or backfill, reducing impact on landfills.  There are also credits available for the reuse, modification, or deconstruction of existing concrete structures on site.  

Decorative or final finish concrete or masonry eliminates potentially hazardous on-site painting and staining, while providing higher quality, longer lasting finishes. Concrete roof tiles can meet ENERGY STAR ® Cool Roof Certification by dissipating solar heat gain, keeping homes cooler. Often, the various ingredients in concrete: cement, water, and large and small aggregates, can all be sourced from within 500 miles of a site, reducing transportation impacts.   

The Standard awards credits for the efficient combination of energy performance and durability. Concrete walls and floors can hold heat because of thermal mass while providing the unsurpassed structural strength of reinforced construction.  They eliminate invasive, expensive, and environmentally hazardous chemical termite treatments needed in many locations with conventional frame construction.  Exterior finishes like stucco and fiber cement siding offer no attraction for insects as well.

The Standard allows building products to be compared and selected for use, based on a Whole Building Life Cycle Assessment.   When selecting products, looking at just the effects of production and assembly tells an incomplete story of overall performance.  Instead, this far more comprehensive “cradle to grave” approach, looks at not just the harvesting, processing, manufacturing, and construction phases, but also includes long term in-place performance, and finally demolition and disposal.  The inherent environmental benefits of concrete out perform all other residential building systems when the full, sustainable story of energy efficient, strong, durable concrete is told.

Energy Efficiency:

Homes built to the Standard must meet the requirements of Energy Star®.  Certification points are available for performance improvements beyond these minimums.  Concrete wall systems with continuous layers of insulation and structure provide thermal benefits and significant reductions in air infiltration.  Add thermal mass benefits from the concrete itself and the result is high performance exterior wall construction which greatly reduces energy consumption. 

With conventional frame construction, a homebuilder must carefully coordinate the installation of insulation and air barrier systems with trades responsible for installing framing, insulation, utilities, and fixtures.  Particular attention must be paid to proper installation and sealing around bathtubs, shower enclosures, alongside stairs, and at intersections with floors and roofs.  Continuous concrete wall systems simplify or eliminate these construction details, saving the builder time and money, while providing the enhanced energy efficiency so important to homes certified under the Standard.

Water Efficiency:

Indoor Environmental Quality:

Use of prefinished concrete systems reduces the amount of paints and stains consumed on site, which can compromise indoor air.   Solid, continuous concrete walls offer a simpler, tighter, fire resistant air barrier separation between living spaces and garages.  Inert concrete countertops are an attractive alternative to conventional tops built with formaldehyde based wood cores.  Many cement based wall systems are insulated with inert and non-VOC emitting products.  Concrete slabs can provide a more durable, more serviceable crawlspace floor, further reducing potential airborne contaminates.   

Bottom Line:

The new ICC 700-2008 National Green Building Standard™ embraces the sustainable value and benefits that concrete systems can provide as an integral part of a certified green residential project.  Why attempt to make yesterday’s frame technology do more than it can easily achieve?  Concrete, with continuous structure and insulation, is a more direct approach to meeting the challenges of high quality, air tight, long lasting, energy efficient construction.  The coordination issues are reduced, the assembly process simplified, which greatly increases the odds of more successful long term performance.   Build it right the first time, and enjoy concrete’s warmth, its comfort, its environmental efficiency for generations.

To learn more about the sustainable benefits of concrete
www.cement.org
www.concretethinker.com

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