Volume 40, Issue 8 August 2005
Know the Codes
Building Envelopes in the Spotlight
by Michael Fischer
The National Institute of Building Sciences (NIBS), in collaboration with other stakeholders, has developed the Whole Buildings Design Guide, (WBDG) a web-based resource that provides state-of-the art information regarding designs and technologies that consider construction projects from a whole-building perspective. NIBS, with funding from the NAVFAC Engineering Innovation and Criteria Office, the U.S. General Services Administration and the U.S. Department of Energy, and the assistance of the Sustainable Buildings Industry Council, offers design guidance, project management and building science reference resources through the WBDG website.
The site also provides links to design tools, including REScheck, a software application used to determine energy code compliance. Other tools available to the user include programs that assist with building life cycle analysis, energy simulators, Leadership in Energy and Environmental Design (LEED) rating software and construction specifications.
Building Design Guidelines
On June 22, 2005, NIBS announced the development of a comprehensive guideline for the design and construction of exterior envelope systems used in office and institutional buildings. Designed for particular use by federal agencies and developed under contract with the Army Corps of Engineers, Naval Facilities Engineering Command, U.S. Air Force, General Services Administration, Department of Energy and Federal Emergency Management Agency, the Building Envelope Design Guide (BEDG) will encourage uniform design and construction criteria for projects built by the federal government.
The BEDG includes envelope systems in below-grade construction, roofing, walls, atria and fenestration. Each system is evaluated for performance criteria including durability, maintainability, moisture protection, thermal performance, fire safety, acoustics and daylighting.
Performance considerations including high wind, flooding and seismic factors are all part of the design parameters of the guide, and other areas of concern include blast safety, chemical/biological/radiological safety and sustainability. For fenestration, including glazing, exterior windows and doors, sloped glazing and curtainwalls, design considerations include occupant safety, weather protection and energy performance.
The BEDG windows section contains design information for waterproof performance, condensation resistance, finish durability, hardware considerations and other administration issues. The section also includes several flashing details and specific prescriptive details, as well as references to industry standards, including ANSI/AAMA/NWWDA/101/I.S.2.
The glazing and sloped glazing sections of the BEDG include information about the specific structural, safety and energy considerations of glazing systems, but also review other design issues including durability of insulating glass units, glass thickness and other important considerations. Unit skylights, however, are not included in the BEDG recommendations.
Curtainwall design criteria receive significant attention in the BEDG as well. Sustainability, maintenance and repair issues, safety, indoor air quality, thermal, condensation and moisture performance considerations are also discussed in detail. Eleven architectural curtainwall details are available for download, and references to various industry standards provide additional resources for the specifier.
Exterior door requirements of the International Building Code (IBC) and the Americans with Disabilities Act (ADA) supersede many design considerations for exit doors, and the BEDG defers to these and other local codes for much of the design considerations. Much of the BEDG exterior door provisions center upon durability and waterproofing, and the parameters include revolving and overhead doors as well. Again, several architectural details, industry standards references and links to industry associations provide the user with additional resources.
There is also a section focused specifically on glazing. It begins with a brief introduction about the history of glass and its uses and then goes into descriptions of the different types of glass products. Descriptions are provided for annealed, heat-strengthened, fully tempered, laminated, coated, tinted and insulating glass units. The section continues with a look at glass fundamentals and discusses topics such as thermal performance, moisture protection, safety, glaring, durability and life expectancy and more. There are also discussions of applications, codes and standards and “emerging issues,” including self cleaning/easy-to-clean glass, photochromic coatings, electrochromic coatings and point-supported glazing.
The BEDG, while still under development, will provide designers of government buildings with information and resources, and help provide consistency in design for federal projects. The NIBS WBDG project is involved in many other areas as well. For example, the WBDG website includes the draft Federal Guide for Green Construction Specs.
These guidelines include reference to the LEED requirements, the Composite Panel Association (CPA) standards for particle board and medium density fiberboard (MDF) that contain formaldehyde emissions maximums, as well as sustainable forest provisions. Wood products (including engineered wood), plastics, adhesives and sealants are all included in the guide, along with specific environmental requirements.
With current Housing and Urban Development requirements for formaldehyde emissions of engineered wood products, and the recent activity by the California Environmental Protection Agency to regulate composite and MDF products containing urea-formaldehyde resins, attention to the emission properties of these products is likely to remain at the forefront of industry focus. For more information, visit the WBDG website:
Michael Fischer serves as director of codes and regulatory compliance for the Window and Door Manufacturers Assn. based in Des Plaines, Ill.
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