Navigating the complexities of LEED v4 with concrete masonry

Photo courtesy CarbonCure

by Jennifer Wagner and Chelsea Code-McNeil
Masonry is inherently a sustainable building material, thanks to its attributes contributing to resiliency—including protection against rotting, mold, and termites—that translates into lower maintenance costs and reduced need for virgin products. Further, its strength and ability to withstand severe weather and fire are helping meet new demands by designers for climate-resistant building materials, while its thermal mass benefits can reduce energy bills and improve indoor thermal comfort.

Some concrete masonry unit (CMU) providers are looking for ways to introduce new elements of sustainability into their manufacturing practices, including use of carbon dioxide (CO2) recycling technology. This process involves retrofitting existing concrete plants with its technology that introduces carbon dioxide (CO2) gas sourced from the smokestacks of local industrial emitters into concrete during production. The CO2 gas undergoes a reaction whereby it becomes chemically converted into a calcium carbonate mineral. This mineralization not only permanently eliminates the CO2, but it also helps to make the concrete stronger, which enables concrete to become a powerful tool in the fight against climate change. The CO2 gas reacts with calcium ions found in cement and undergoes a reverse calcination reaction, which results in the formation of a calcium carbonate mineral. (The mineralization process enhances the early compressive strength of ready-mixed concrete by approximately 10 percent.)

Acknowledging the continually greener innovations within masonry manufacturing, this article looks at how these Division 04 materials can contribute to points in the latest, forthcoming iteration of the U.S. Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design rating program, LEED v4.

Proponents of the LEED system say it has always made it a priority to propel and push industry to redefine what makes a material sustainable for manufacturers, designers, and building owners. The definition of what makes a building material green has evolved in the newest version, as LEED v4 will take into account a broad range of considerations, including regional sourcing, recycled content, and environmental impact over a product’s lifecycle.

Introducing LEED v4
LEED v4 will take a more holistic approach to defining a green building material with a particular focus on lifecycle impacts in addition to supply chain management, taking the program’s scope one step deeper into the manufacturing process. This change is expected to influence the information designers and architects are requesting from manufacturers. Architects are requiring more rigorous information from manufacturers, by requesting them to collect information from outside their localized manufacturing processes.

In the past, self-declared recycled content and bare-bones regional declarations were enough to meet credit requirements, but under LEED v4 this will no longer be the case. The information being requested will take time to collect, so manufacturers looking to stay ahead of the curve should start this process now during the transition period from the current 2009 version of LEED to LEED v4, which comes into full effect on October 31, 2016.

Now that LEED is redefining what makes a material sustainable, less emphasis is being put on a product’s individual attributes. This new emphasis is reflected in the redistribution of points in the Materials & Resources (MR) credits. For example, under LEED 2009, six points (from three separate credits) could be awarded for products with recycled (i.e. MRc4, Recycled Content), regional (i.e. MRc5, Regional Materials), or Forest Stewardship Council (FSC) certified content (i.e. MRc7, Certified Wood), whereas in LEED v4 the individual attributes of recycled and FSC content are combined, and “Regional materials” is not a separate credit, but is rather introduced as a value multiplier that applies to several credits.

LEED v4’s MR category has two prerequisites (i.e. Storage and Collection of Recyclables and Construction and Demolition Waste Management Planning) and five credits. Three of those credits address different aspects of building product disclosure and optimization, and are worth up to two points each. Those three credits, which acknowledge a designer’s use of sustainable products, are:

  • Building Product Disclosure and Optimization−Environmental Product Declarations;
  • Building Product Disclosure and Optimization−Sourcing of Raw Materials; and
  • Building Product Disclosure and Optimization−Material Ingredients.

The other two credits under LEED v4’s MR category are:

  • Building Life-cycle Impact Reduction (worth up to five points, it encourages the adaptive reuse of materials or optimizes the environmental performance of products and materials); and
  • Construction and Demolition Waste Management (up to two points).

According to the LEED credit language, the intent of the three Building Product Disclosure and Optimization credits is “to encourage the use of products and materials for which life-cycle information is available and that have environmentally, economically, and socially preferable life-cycle impacts.” Further, their intent is to reward project teams for selecting products according to specific criteria. For example, the Environmental Product Declarations credit calls for products “from manufacturers who have verified improved environmental life-cycle impacts,” whereas the Sourcing of Raw Materials credit lauds materials “verified to have been extracted or sourced in a responsible manner.”

Similarly, the material ingredients credit recognizes products “for which the chemical ingredients in the product are inventoried using an accepted methodology and for selecting products verified to minimize the use and generation of harmful substances. To reward raw material manufacturers who produce products verified to have improved life-cycle impacts.”

So how do CMUs fit into all of this?

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