Designing for Sustainability:

Cementitious-based Building Materials Contribute to LEED® Credits
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Sponsored by Lafarge

Energy & Atmosphere (EA)

Minimum Energy Performance (EA Prerequisite 2)
Intent: Establish the minimum level of energy efficiency for theproposed building and systems.

This prerequisite requires compliance with ASHRAE/IESNA Standard 90.1-2004 or the local energy code, whichever is more stringent.

Optimizes Energy Performance (EA Credit; 1 to 10 points)
Intent: Achieve increasing levels of energy performance above the baseline in the prerequisite standard to reduce environmental and economic impacts associated with excessive energy use.

Ninety percent of the environmental impact of CO2 associated with buildings arises from heating, cooling and lighting during their operational lifetime. Concrete buildings have the ability to absorb and release heat, via thermal mass effect, which means that less energy is needed for heating or cooling.

A PCA study that modeled energy performance of concrete buildings (www.concretethinker.com) shows that the effect of thermal mass in concrete-framed buildings combined with thermal improvements to the building envelopes lowers energy cost up to 23 percent relative to baseline steel-framed insulated buildings. This is an energy savings that qualifies for up to four (4) LEED-NC v2.2 points.

The concrete thermal mass of a building contributes to EA credits in three ways. First, thermal mass moderates indoor temperature fluctuations, thus reducing spikes in temperature. Second, massive wall and roof elements slow the transfer of heat through the building envelope. Third, concrete thermal mass can store energy, thus shifting demand to off-peak periods.  In addition, insulated concrete wall systems reduce air infiltration. Their solid wall assemblies and high R-values from rigid insulation provide airtight building envelopes that increase energy efficiency.

A number of concrete construction methods may contribute to thermal mass. Lafarge's Buffenbarger lists tilt-up walls, insulating concrete forms (ICFs), precast sandwich panels, insulated concrete masonry unit walls, cast-in-place concrete with removable formed walls, autoclaved aerated concrete panels, insulated cement siding, shotcrete (sprayed concrete), and stucco.

Materials & Resources (MR)

Building Reuse: (MR Credit 1.1, Credit 1.2 and Credit 1.3; 1-3 points) Maintain 75 percent or 95 percent of Existing Walls, Floors & Roof; 50 percent of Interior Non-Structural Elements.
Intent:Extend the life cycle of existing building stock.

Well-constructed building envelopes and structures of concrete, concrete masonry units; concrete roofing elements; interior floors and walls and other structural materials that contain concrete and cementitious building materials can be left in place during major refurbishment. The reuse of existing structures provides multiple benefits including land reuse and preservations of greenfields, raw material conservation, reduced strain on landfills, as well as lowered embodied energies in their deconstruction.

Construction Waste Management (MR Credit 2.1 and Credit 2.2; 1-2 points) Divert 50 percent or 75 percent in weight or volume from disposal.
Intent: Divert construction, demolition and land-clearing debris from disposal in landfills...Redirect recyclable recovered resources back to the manufacturing process.

Concrete and concrete masonry materials may be recycled, crushed and reused on site.

Materials Reuse (MR Credit 3.1 and Credit 3.2; 1-2 Points) 5 percent or 10 percent materials reuse, based on cost. 
Intent: Reuse building materials and products in order to reduce demand for virgin materials.

Credits apply to individual components and include incoming material from the marketplace and materials salvaged from on-site demolition or renovation.

 

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Originally published in Architectural Record
Originally published in April 2008

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