Cast Stone and LEED® v4
The U.S. Green Building Council (USGBC) developed the LEED rating system; LEED stands for Leadership in Energy and Environmental Design. A separate entity, the Green Building Certification Institute (GBCI) administers LEED project certification and professional credentialing programs. The LEED certification program was developed to provide a method to define and measure what are commonly called “green buildings.” From its inception as a pilot program for new buildings in 1998 to the present, the LEED certification program has expanded and grown dramatically. There are numerous LEED rating systems organized by type of construction and end use, including:
The most widely used rating system in the U.S. is currently LEED® BD+C: New Construction™ (LEED for New Construction) though LEED Existing Buildings: Operations and Maintenance is also widely used. While each rating system is distinct, most of the topics covered can be grouped into the same general categories. This Bulletin examines the requirements of LEED v4 for BD+C: New Construction and its relevance to cast stone.
The Use of Cast Stone
Figure 1: LEED for New Construction 2009 point distribution
Figure 2: LEED for New Construction 2009 certification levels
Earning LEED Points
Location and Transporation (LT)
LT Credit 4 - Surrounding Density and Diverse Uses (1-5 points) – the intent of this credit is to encourage development in urban areas with existing infrastructure. Building products do not directly contribute to this credit. However, masonry materials are often used for urban infill development because of their appearance, size and scale, fire ratings, as well as for benefits in space required for construction. Cast stone masonry can often be installed without the use of a crane, thus helping to minimize the need for large equipment on site.
Sustainable Sites (SS)
SS Credit 5: Heat Island Reduction (2 points) – the intent of this credit is to reduce the retention of heat due to dark colored surfaces by providing shade, using materials that meet solar reflectance criteria, or other strategies for the roof and non-roof areas such that their weighted area exceeds the sum of the area of site paving and total roof area. Cast stone used as caps on landscaping walls, stair treads, and pavers on the site or on the building roof can meet the criteria for earning this point.
This credit requires that paving materials have a three-year aged solar reflectance (SR) value of at least 0.28. If three-year aged value information is not available, materials must have an initial SR of at least 0.33 at installation. A study [Ref. 1] by the Portland Cement Association of 135 concrete specimens all had a SR of at least 0.33. One specimen made with white Portland cement had a SR of at least 0.64. Cast stone elements typically meet the LEED requirements for solar reflectance, especially if white Portland cement is used.
Energy & Atmosphere (EA)
EA Prerequisite 2: Minimum Energy Performance (0 points) – as part of a masonry wall, cast stone can help mitigate temperature swings and achieve the required energy performance particularly when interior masonry is left exposed.
EA Credit 2: Optimize Energy Performance (up to 18 points) – as part of a masonry wall, cast stone can be used to help reduce the amount of energy consumed by the building. The benefit of thermal mass is best recognized when using energy modeling tools such as BLAST or EnergyPlus.
Materials & Resources (MR)
MR Credit 1: Building Life-Cycle Impact Reduction (up to 5 points) – this credit incorporates the former Building Reuse and Material Reuse credits, and gives more weight (points) to reuse of whole buildings than the previous version of LEED. This credit contains four different paths, with the first three focused on building and material reuse and the last on new construction. Masonry buildings, many of which incorporate cast stone details, are good candidates for reuse. Cast stone features on the building interior such as columns, fireplace mantels and surrounds, stair treads, etc. are also good candidates for reuse. Anchoring details that allow for disassembly can facilitate this. Larger elements not set in mortar are especially suited for salvaging. In addition, cast stone can be repaired to conceal damage that may occur during disassembly and removal.
MR Credit 2: Building Product Disclosure and Optimization – Environmental Product Declarations (2 points), is a new credit in LEED v4. This credit has two options, worth one point each. The first option focuses on reporting of environmental impact data via an Environmental Product Declaration (EPD), while the second rewards improved performance in specified environmental impact categories through life cycle assessment. Cast stone elements produced by manufacturers having an EPD can count toward this credit.
MR Credit 3: Building Product Disclosure and Optimization – Sourcing of Raw Materials (up to 2 points) has two different options worth one point each. Option 1, Raw Material Source and Extraction Reporting, requires use of at least 20 different permanently installed products sourced from at least 5 different manufacturers that have publicly released a report from their raw material suppliers. Third-party verified corporate sustainability reports are counted in full. Self-declared reports count as only ½ value, so for example, if only self-declared reports are used, 40 products would be required instead of 20.
The second option incorporates aspects of the recycled content, rapidly renewable, certified wood and material reuse credits found in LEED 2009. Option 2, Leadership Extraction Practices, requires use of products that meet at least one of the responsible extraction criteria below for at least 25%, by cost, of the total value of permanently installed building products in the project. When calculating the value of the products, those demonstrating extended producer responsibility are valued only at 50% of their cost. Other extration criteria are valued at the full amount.
Cast stone elements can help earn this credit when they incorporate recycled materials into their mix, most often as aggregates or supplementary cementitious materials. Pre-consumer (post-industrial) recycled materials that may be incorporated into cast stone include recycled aggregate or slag that can be used as an aggregate, and supplementary cementitious materials like fly ash. Color may be affected by incorporation of certain recycled materials, so contacting the cast stone manufacturer is recommended.
MR Credit 4: Building Product Disclosure and Optimization – Material Ingredients (up to 3 points) – This credit has three options worth 1 point each. All three options require documentation of the raw material ingredients for building products. Several chemical and ingredient screening programs are listed as compliance paths including the GreenScreen™ for Safer Chemicals, Cradle to Cradle certification, and the Health Product Declaration (for more information see Resources), but Material Safety Data Sheets (MSDS) are not considered compliant with this credit. Cast stone producers that provide the chemical inventory for their products using the Chemical Abstract Service Registry Numbers (CASRN) can count toward Option 1 of this credit.
MR Credit 5: Construction and Demolition Waste Management (up to 2 points) – The intent of this credit is to eliminate construction waste from landfills. Up to two points can be earned for recycling or salvaging specified amounts of construction waste, or two points can be earned if the project does not generate more than 2.5 lbs of construction waste/ft2 of the building's floor area. On-site waste from cast stone elements is limited primarily to packaging materials. Cast stone elements are carefully detailed and exact amounts are delivered to the site so that waste stone is nearly eliminated helping meet the reduction of total waste goal. Any waste cast stone elements that are present can be crushed and used as aggregate or fill.
Indoor Environmental Quality (IEQ)
IEQ Credit 2 – Low-Emitting Materials (up to 3 points) – This credit focuses on volitile organic compound (VOC) emissions, rather than content. It also explicity lists stone, glass, concrete, and clay brick as “…inherently non-emitting and comply without any testing if they do not include integral organic-based surface coatings, binders, or sealants.” Thus cast stone elements without integral organic-based materials used on exposed interior walls or floors meet this credit without any testing required.
Designers utilizing the LEED v4 for BD+C: New Construction rating system are encouraged to contact cast stone manufacturers to determine relevant practices for achieving LEED credits and to look for opportunities and the synergy that can occur when cast stone is chosen for use on a project.
2. LEED v4 User Guide (June 2013), U.S. Green Building Council, Washington, DC, http://www.usgbc.org/resources/leed-v4-user-guide.
Ms. Subasic has been a member of The Masonry Society (TMS) since 1992 and a member of the Board of Directors since 2002. She serves on the Architectural Practices committee, the Design Practices committee, and is a founding member of the Sustainability Committee. Ms. Subasic also represents TMS on the U.S. Green Building Council and is a member of the Green Globes ANSI Standard Development Committee.