By Claude Goguen, P.E., LEED AP
Since its unveiling in 2000, Leadership in Energy and Environmental Design (LEED) has become a part of building construction vernacular in the United States and around the world. The U.S. Green Building Council (USGBC) runs LEED, which is designed to save money, energy and water resources, and to promote healthy, sustainable and environmentally friendly buildings.
A growing number of agencies support LEED benchmarks, including construction industry associations; state, federal and local governments; private organizations; and engineers and architects across the globe. Today’s new structures routinely include requirements for material suppliers and contractors to construct buildings that qualify for the maximum attainable LEED credits.
No. 1 international green-building certification program
From its humble beginnings in the late 1990s, LEED has grown more rigorous in its requirements. It is now recognized internationally as the main third-party certification for green buildings, currently certifying 1.7 million sq ft of building space every day. More than 54,000 projects are participating in the current version, LEED 2009, totaling more than 10.1 billion sq ft of construction space.
While some in the construction industry embrace LEED, others find its rating system unnecessarily complex and unfairly exclusive to certain building products. But love or hate it, LEED increasingly dictates new project materials, methods and designs.
After a couple of years of deadline extensions and six public comment periods, 86% of USGBC members voted to approve the latest version, LEED v4. According to the USGBC, the launch of LEED v4 is “designed to drive innovation in every aspect of the building lifecycle.”
The USGBC is taking a phased approach to LEED v4. This means that rather than requiring all projects to comply immediately, it is giving the marketplace time to become familiar with the basis of its concepts and theories. Project teams can register their projects under LEED 2009 until June 1, 2015.
hose familiar with previous versions of LEED will recognize the same fundamental structure (prerequisites and credits, 100 base points, regional priority credits and pilot credits); however, LEED v4 has more emphasis on USGBC’s goal of reducing carbon emissions, and this means increased energy efficiencies across the board. Consequently, LEED v4 had adopted ASHRAE(i) standards.
LEED v4 is technically more rigorous, with major changes including:
- Expanding compliance for LEED market sectors to include: data centers, warehouses and distribution centers, hospitality projects, existing schools, existing retail, and new compliance for mid-rise projects
- A separate new credit category for Location and Transportation (smart growth principles including reuse of existing structures and pedestrian-friendly designs) and a new Environmental Site Assessment credit
- A new prerequisite for water metering and new credit for water cooling towers
- A construction Demolition and Waste Management prerequisite
- A reworked Materials and Resources section with a focus on waste reduction and reuse
- Revised credit weightings with point distribution that will more closely tie the rating system requirements to the priorities articulated by the USGBC community
- New prerequisites and new, rearranged and merged credits across LEED categories, including changes in the rating systems
- Changed point values for each rating system, with LEED points associated with each credit and option of the rating system
Under LEED Building and Design, USGBC’s increased emphasis on carbon reduction (global warming) will be seen in designs, material selection, modeling and project delivery methods. These changes have resulted in controversy, especially the new credit to minimize human health risks (Building Product Disclosure and Optimization, and Material Ingredients).
Using precast concrete to meet the demands of LEED v4
Some of the changes affecting the use of precast concrete include:
- Site Development – Protect or Restore Habitat (formerly SS 5.1): The requirement is to preserve and protect from all development and construction activity 40% of the green field area on the site (if such areas exist). Precast will still contribute in this category because it’s made to order, reduces storage space on site and minimizes site disturbance.
- Rainwater Management (combined former 6.1, “Stormwater Design – Quality Control,” and 6.2, “Stormwater Design – Quantity Control”): Precast will still contribute through the use of stormwater products to manage the runoff.
- Heat Island Reduction: Precast concrete has a higher solar reflectance than many other materials, which is beneficial in reducing the heat island effect.
- Building Product Disclosure and Optimization – Environmental Product Declarations: Multi-Attribute Optimization – This credit rewards the use of products that comply with one of a few criteria including products sourced (extracted, manufactured, purchased) within 100 miles of the project site. Precast concrete manufacturers are often located within short distances from the project.
- Building Product Disclosure and Optimization – Sourcing of Raw Materials: Leadership Extraction Practices – This credit awards points based on the use of products that meet at least one of six responsible extraction criteria for at least 25%, by cost, of the total value of permanently installed building products in the project including recycled content. Precast concrete includes pre- and post-consumer recycled content mostly through the use of supplementary cementitious materials and reinforcing.
- Construction and Demolition Waste Management: Reduction of Total Waste Material – Do not generate more than 2.5 lbs/sq ft of construction waste on the building’s floor area. The use of precast concrete significantly reduces construction waste, because it arrives on site ready to be installed.
- Regional Materials: The “regional” definition will no longer be 500 miles. It is currently based on “Regional Core Based Statistical Area,” updated Dec. 1, 2009, by the U.S. Office of Management and Budget.
- Thermal Comfort (renamed from “Controllability of Systems – Thermal Comfort,” combined with “Thermal Comfort – Design Requirements for Achievement”): Design of heating, ventilation and air conditioning (HVAC) systems and the building envelope will need to meet the requirements of ASHRAE Standard 55-2010, “Thermal Comfort Conditions for Human Occupancy.”
- Precast Enclosures: Precast enclosures will contribute due to concrete’s thermal mass properties.
Environmental Product Declarations
LEED v4 also awards credits for the use of Environmental Product Declarations (EPDs) for products and Life Cycle Assessments (LCAs) for whole buildings as a way to demonstrate transparency and superior environmental performance. Similar to a food nutrition label, an EPD reports environmental impacts such as carbon footprint, acidification or ozone depletion potential. EPDs list quantified life-cycle product data, and the product or brand producer owns the labels. In essence, EPDs are eco-labels, and many believe they will be required for all building products in the future.
Product Category Rules (PCRs) govern how LCAs and EPDs are written. The PCRs are developed for a broad product type such as vinyl siding, asphalt roof shingles or precast concrete. NPCA is working with two other industry partners to create a North American PCR for precast concrete.
The green building industry is continuing to grow, and LEED has been a big part of that growth. LEED v4 ushers in a major emphasis on carbon reduction, and with it come new requirements for increased energy efficiency in all aspects of new construction.
Claude Goguen, P.E., LEED AP, is NPCA’s director of Technical Services and Sustainability. For questions about this article, please contact Claude at (317) 571-9500 or [email protected].
(i) ASHRAE = The American Society of Heating, Refrigerating and Air-Conditioning Engineers