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Contact: David Walker
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WASHINGTON, DC  (December 17, 2009) – The National Glass Association (NGA), the leading business organization representing the North American glass industry, joined other industry associations in submitting comments in the public review for American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) standard 90.1. The revision to ASHRAE 90.1 aims to increase building energy efficiency by 30% by the year 2030. The standard, which is published every 3 years, is the basis for both state energy codes and utility rebate programs. 

NGA’s comments, developed in cooperation with the American Architectural Manufacturers Association (AAMA), the Insulating Glass Manufacturers Alliance (IGMA), and the Glass Association of North America (GANA), included the following:

  • U-Factor and SHGC values
    The National Glass Association asserts that the U-factor and SHGC values listed in the addendum should be changed to the values proposed by NBI and AIA in EC165 to the IECC. The proposed values are appropriate and have been accepted with broad support at the ICC preliminary hearings. Adopting these agreed upon values in ASHRAE 90.1 will provide consistency within the standards and the industry.

  • Window to Wall Ratio
    The current proposal reduces the window area in construction projects using the prescriptive path from 40% to 30%. The NGA does not support this reduction in the window to wall ratio. There appears to be no data to support lowering the percentage. The NGA maintains that the window to wall ratio in ASHRAE 90.1 should be left at 40% while research is completed.

  • Light to solar gain
    The use of VT/SHGC or LSG criterion only saves energy if lighting controls are present. Therefore, a minimum center of the glass LSG value should be required when paired with lighting controls that enable the capture of energy savings through natural daylight. The NGA suggests a modification to ASHRAE 90.1 that requires compliance with VT/SHGC criterion for the entire product only where lighting controls are used and requests that ASHRAE 90.1 reflect the DOE’s requirements to ensure consistency in the industry.

The proposed revision was opened for public review in November 2009. The committee will review comments in January 2010, with the goal of completing the new version of the standard in June.

About NGA
Founded in 1948, the National Glass Association is the largest trade association representing the glass and window and door industries. Based outside Washington, DC, and representing over 3,000 member companies and locations, NGA offers certification and education and training, including and – state-of-the-art online training resources. NGA publishes the industry’s leading trade magazines: Glass Magazine® and Window & Door®; and e-newsletters: e-glass weekly™, WDweekly™, and For Technicians Only e-bulletin™. In addition, NGA serves the industry and general public with its Web sites:,,,,, and NGA also hosts the industry’s premier annual trade event: GlassBuild America: The Glass, Window & Door Expo®. The Window & Door Dealers Alliance, an organization for independent window and door dealers, is an initiative of the NGA. For more information on NGA, visit