LEED and Masonry
By Christine A. Subasic, P.E., Leed AP
Masonry and sustainable building design seem like a natural fit. Masonry, with its durability, local or regional manufacturing, and thermal mass characteristics, meets many of the goals of sustainable building design. With the development of the LEEDTM Green Building Rating System, interest in sustainable design has taken off.
What is LEED?
LEED refers to the Leadership in Energy and Environmental DesignTM Green Building Rating System developed by the U.S. Green Building Council (USGBC). LEED is a national voluntary program to define and measure what constitutes a "green" building. There are LEED rating systems for new construction and major renovations (LEED-NC), existing buildings (LEED-EB) and commercial interiors (LEED-CI). Committees are currently developing rating systems for multiple buildings (LEED-MB), core and shell development (LEED-CS), neighborhood development (LEED-ND) and homes (LEED-H).
The goals of the LEED certification process are to improve occupant wellbeing, environmental performance and economic returns of buildings. Buildings are LEED-certified if they achieve at least 26 points out of a possible 69. Silver certification is awarded for projects with 33 to 38 points. Projects with 39 to 51 points are LEED Gold-certified. The highest level of certification, for projects earning 52 points or more, is Platinum.
Masonry Contributions to LEED Credits
The LEED-NC rating system is divided into five environmental categories, each with multiple parts or credits to recognize sustainable building practices, plus a sixth category to recognize innovative designs that greatly exceed the LEED credit requirements or that address sustainable issues not covered by the LEED rating system. The categories are:
- Sustainable Sites (14 points available)
- Water Efficiency (5 points available)
- Energy and Atmosphere (17 points available)
- Materials and Resources (13 points available)
- Indoor Environmental Quality (15 points available)
- Innovation and Design Process (4 points available + 1 point for a LEED-accredited professional on the design team)
1. Sustainable Sites (SS)
By using permeable concrete or brick masonry pavements or open cell concrete masonry pavers, masonry can contribute up to three points in this category.
Credit 6.1: Stormwater Management - Rate and Quantity
The intent of this credit is to limit disruption and pollution of natural water flows by managing or eliminating stormwater runoff, increasing on-site infiltration and eliminating contaminants. One point is awarded if, for a site with an existing imperiousness less than or equal to 50%, the post-development 1.5 year, 24-hour peak discharge rate does not exceed the pre-development rate; or if, for a site with an existing imperviousness greater than 50%, the rate and quantity of stormwater runoff is decreased by 25%.
Credit 6.2: Stormwater Management - Treatment
The intent of this credit is the same as for Credit 6.1. One point is awarded for stormwater treatment systems designed to remove 80% of the average annual post-development total suspended solids (TSS) and 40% of the average annual post-development total phosphorous (TP). Recommended best management practices for achieving this credit include the use of porous pavements.
Credit 7.1: Heat Island Effect - Non-Roof
The intent of this credit is to reduce heat islands to minimize impact on microclimate and human and wildlife habitat. One point is awarded if shade and/or light-colored/high-albedo materials and/or open-grid pavement are provided for at least 30% of the site's non-roof impervious surfaces. Or one point can be awarded for the use of an open-grid pavement system (less than 50% impervious) for a minimum of 50% of the parking lot area.
3. Energy and Atmosphere (EA)
Masonry can contribute to achieving points in this category by harvesting site energy (using passive solar designs) and decreasing the size of the building HVAC system. The thermal mass inherent in masonry reduces temperature swings, stores heat/cooling for release at later times, and reduces peak energy loads. These strategies can reduce the size of the HVAC system required.
Credit 1 - Optimize Energy Performance
This is intended to achieve increasing levels of energy performance above the prerequisite standard. One to 10 points can be awarded for improvements of 15 to 60% above the standard for new buildings or 5 to 50% improvement for existing buildings. The baseline standard used is ASHRAE /IESNA 90.1-1999. Improvements in performance are measured using the Energy Cost Budget Method found in Section 11 of the ASHRAE standard.
4. Materials and Resources (MR)
Masonry can contribute up to 11 points (out of 13) toward LEED certification in this category. Credits are given for building materials harvested and manufactured locally, for materials with recycled content, and for reuse of building materials - all areas to which masonry can contribute.
Credit 1 - Building Reuse
The intent of this credit is to extend the life cycle of existing building stock, conserve resources, retain cultural resources, reduce waste and reduce environmental impacts of new buildings. Credit 1.1 awards one point for 75% reuse of existing walls, floors and roof. Credit 1.2 gives one additional point for maintaining 100% of the existing walls, floors and roof. Changes proposed for LEED version 2.2 lower these thresholds to 40% and 80% respectively, making it easier to qualify.
Credit 1.3 awards one additional point for reuse of 50% of interior non-structural elements. Non-structural masonry walls and floors can contribute to this point.
Credit 2 - Construction Waste Management
The intent of this credit is to divert construction, demolition and land clearing debris from landfill disposal. Scraps and broken pieces of concrete masonry can be crushed and used for aggregate or fill. Clay brick scraps can be crushed and used for landscaping as brick chips. Intact, unused masonry units can be saved to use on another project, or donated to Habitat for Humanity or other charitable organizations. One point is awarded for diversion of 50% of the construction, demolition and land clearing waste (Credit 2.1). One additional point is awarded for diverting 75% (Credit 2.2). Calculations can be done on a weight or volume basis.
Credit 3 - Resource Reuse
This credit is intended for reuse of salvaged materials and products to reduce the demand for virgin products. Materials salvaged on site do not apply to this credit, but do count toward Credit 1 - Building Reuse. Masonry materials such as brick can be salvaged, but the Brick Industry Association warns against their use. Used brick may not meet the requirements of present-day specifications and may not bond properly. Paver brick that are salvaged and used for interior applications on a new building meet the intent of this credit. Up to two points can be earned for use of salvaged building materials for 5% and 10% of building materials (Credits 3.1 and 3.2).
Credit 4 - Recycled Content
This credit is intended to increase demand for building products that incorporate recycled content materials, therefore reducing impacts resulting from extraction and processing of new virgin materials. This credit awards up to two points for using building products that incorporate recycled content materials. Because of the inert nature of masonry products, they are ideal candidates for incorporating recycled materials. The requirement for one point is that materials with the sum of post-consumer recycled content plus 1/2 the post-industrial content constitute at least 5% of the total value of materials in the project (Credit 4.1). If the sum of post-consumer recycled content plus 1/2 the post-industrial content equals 10% or more, one additional point is awarded (Credit 4.2).
Concrete masonry units often incorporate recycled materials. According to the NCMA, supplementary cementitious materials such as fly ash, silica fume and slag cement are considered post-industrial materials. Concrete masonry that incorporates recycled concrete masonry, glass, slag or other recycled materials as aggregate qualify as post-consumer. (TEK 6-9A)
Clay brick often incorporate recycled brick ground and used as grog. If reclaimed from a job site, this material can qualify as post-consumer recycled content. Some manufacturers use bottom ash, a post-industrial waste, for 10 to 12% (by weight) of the clay body. Other post-industrial materials used include fly ash and even sludge. Because of the inert properties of brick, even contaminated soil and sawdust are used. One company uses waste from a nearby ceramic whiteware manufacturer as grog.
Mortar may contain recycled materials such as fly ash. Steel reinforcing bars used in reinforced masonry may contain post-consumer or post-industrial materials.
Credit 5 - Regional Materials
This credit encourages the use of building materials that are extracted and manufactured within the region, thereby supporting the regional economy and reducing the environmental impacts resulting from transportation. Masonry products can contribute to one point when 20% of the building materials and products are manufactured within a 500-mile radius of the project site (Credit 5.1). One additional point is earned if the regionally manufactured materials use a minimum of 50% of building materials that are extracted, harvested or recovered within 500 miles of the project site (Credit 5.2). Changes to the specifics of this credit are proposed for LEED 2.2
6. Innovation in Design (ID)
The intent of this category is to recognize exceptional performance beyond the requirements in LEED or reward innovations in categories not specifically addressed by LEED. Credit 1 awards one point for each innovation up to a total of four points. Possible areas where masonry can contribute include:
- acoustic performance
- life-cycle cost and durability
- efficient use of materials with prestressed or reinforced masonry
- improved air quality by reducing the need for paint or interior coatings (thereby reducing volatile organic compounds, or VOCs) and by reducing the possibility of mold growth
Such credits require the applicant to write the intent and requirements of the credit. These credits are typically awarded for having a building-wide approach that addresses a sustainable feature such as those listed above. For example, a credit could be written for improved air quality beyond that required in LEED EQ (Indoor Environmental Quality) Credit 4 - Low Emitting Materials by choosing materials throughout the building that do not require paint or coatings such as glazed masonry in toilet and janitorial rooms, brick pavers for flooring, architectural concrete masonry for walls, etc. All materials used in the building would be considered, and masonry could be a large contributor to achieving the intent.
Credit 2 gives one point for having a LEED-accredited professional on the design team.
Conclusion
The Masonry Society (TMS) has formed a Sustainability Subcommittee chaired by Pat Rand to support the use of masonry in sustainable design. This subcommittee falls within the purview of the Architectural Practices Committee chaired by Rochelle Jaffe. To participate on these committees or for further information contact The Masonry Society at www.masonrysociety.org.
About the Author
Christine Subasic, P.E., LEED AP, of C. Callista Subasic is a masonry expert. Earlier this year, she was chosen to represent The Masonry Society with the U.S. Green Building Council.
