NGA comments on ASHRAE 90.1 public review

December 17, 2009

The National Glass Association, McLean, Va., 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, according to a Dec. 17 release. The revision to ASHRAE 90.1 aims to increase building energy efficiency by 30 percent by the year 2030. See story. The standard, published every three 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, the Insulating Glass Manufacturers Alliance, and the Glass Association of North America, 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 percent to 30 percent. 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 percent 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

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.