Technical Details: Leadership in Energy and Environmental Design
The LEED ProgramThe LEED Program (Leadership in Energy and Environmental Design) was developed by the U.S. Green Building Council. The USGBC is a nonprofit coalition of building professionals representing all segments of the industry. Members work together to promote the design and development of environmentally and economically responsible buildings. Through the USGBC, LEED has been developed as a voluntary national standard for the development of high performance, sustainable buildings. The program covers new construction (commercial and residential) and major renovation projects.
LEED was created to provide a definition of "green building" and establish a common standard of measurement for the process. The USGBC also hopes that this program will promote integrated and whole-building green design practices. This goal can be achieved by raising the consumer's awareness of benefits associated with green building practices.
The main objective of the LEED program is to decrease energy consumption and lessen the environmental impact of buildings. The LEED program is structured to provide the proper assessment of a building's performance to ensure that it meets sustainability goals. The sustainability goals are established from scientific standards and are met through emphasis of state-of-the-art strategies throughout the whole building process. Energy savings can be realized through several avenues including sustainable site development, water savings, energy efficiency, materials selection and indoor environmental quality. In addition to promotion of green building practices, the USGBC also provides expertise in these areas by offering training, resources, project certifications and professional accreditation.
LEED RatingsThe basis of the LEED program is through the issuance of a rating for a building based on its sustainability and energy efficiency. The ratings are based on a set of performance standards for the sustainable operation of existing buildings. The LEED-EB criteria cover building operations and systems upgrades in existing buildings where the majority of interior or exterior surfaces remain unchanged.
The rating is based on points accumulated through a number of sustainable or energy efficiency categories. A building can achieve one of four levels of certification based on the accumulated points. The Platinum Level is 52 points or more, the Gold Level is 39 to 51 points, the Silver Level is 33 to 38 points, and LEED Certified is 26 to 52 points.
Even though this is currently a voluntary program, some states and municipalities have adapted LEED as part of their building code, and it has become a requirement on most Federal buildings. In some states, the local energy companies are providing rebates and discounts to building owners that reach certain LEED levels. This trend is expected to continue, particularly at the state and local levels.
The higher LEED levels indicate higher energy efficiency, which also translates to higher energy savings (lower costs) to the building owner over the life of the building. There are seven LEED categories from which points are allocated. The categories are:
- Sustainable Sites 14 points
- Water Efficiency 5 points
- Energy and Atmosphere 17 points
- Materials and Resources 13 points
- Indoor Environment 15 points
- Design Process & Innovation 4 points
- LEED Accredited Professional 1 point
It is the responsibility of the building owner to register the project with the USGBC during the design phase, to select qualified/certified products and to submit documentation at or near building occupancy.
LEED and RoofingRoofing materials can have an impact in three of these categories: Sustainable Sites, Energy and Atmosphere, and Materials and Resources. Roof systems can have an impact through thermal capacity, reflectivity and emissivity. Thermal capacity is achieved through higher R-values, predominately from insulation. High thermal value insulation will reduce heat loss in the winter months, which decreases heating costs and energy capacity. There are currently no national code regulations regarding minimum R-values for low-slope roof systems. Some states and municipalities have enacted their own requirements, which are typically R-19 or higher.
Reflectivity ratings are based on the roof surface's ability to reflect ultraviolet rays from the sun. Studies have indicated that reflective surfaces will keep the building cooler in the summer, decreasing the use of air conditioning and cutting cooling costs and energy capacity. The Energy Star® Program, which was developed by the U.S. Department of Energy in the mid-1990s, establishes the reflectivity rate of a roof surface for low-slope (less than 2:12) roof systems at 0.65 the first three years and 0.50 after three years. LEED provides points based on this program. There is currently great debate in the industry regarding this program; however, some municipalities have taken steps to enact it as code and all indications are that the Energy Star program-in some form-will become part of the national code.
Emissivity is the ratio of radiation emitted by a blackbody or a surface and the theoretical radiation predicted by Planck's law. Blackbody emissivity is frequently referred to as a single number. A material's surface emissivity is a measure of the energy emitted when a surface is directly viewed. Surface emissivity is generally measured indirectly by assuming that e = 1 - reflectivity.
A single energy bounce is measured and the reflected energy is measured. The LEED emissivity rating for roofing is a minimum of 0.90 based on ASTM E 408.
Due to these regulations, there has been a concentrated effort by roofing manufacturers to produce products that meet Energy Star requirements.
The use of these products contributes to LEED points for green buildings. LEED points can also be achieved if any of the roof system materials are manufactured within 500 miles of the building site. Additional points can be accumulated if a member of the project team is a LEED-accredited professional and for exceptional performance in innovation of application or design. Recyclable materials or materials manufactured from recycled products (some perlite and fiberboard insulations qualify) can also provide LEED points on a project.
At this time, these types of programs are voluntary standards that have not been incorporated into national codes. However, some states-such as California and Nevada-and some cities-such as Chicago-have begun enacting them (or variations of them) as local codes in an effort to promote green and cool buildings.
California has passed Title 24, which is a regulation that sets energy efficiency design and construction standards for residential and nonresidential buildings. The intent of this legislation is to reduce the peak energy demands that created power blackouts in 2000 and 2001. Title 24 is the latest revision of the Warren Alquist Act that was passed in 1978 and is updated every three years. The next revision takes effect in October of 2005 and stipulates all roofs must meet minimum standards established by the Cool Roof Rating Council (CRRC), which are initial emissivity rating of 0.75 and initial reflectivity rating of 0.70.
For further information regarding the LEED program, visit the U. S. Green Building Council's Web site at www.usgbc.org.