Proposals to Lower U-Factor and SHGC Pass, Raising Life Safety Concerns
October 29, 2010

During yesterday’s code hearings a motion carried to disapprove proposal EC25, which would have lowered the solar heat gain coefficient (SHGC) in climate zones 1, 2 and 3 from .30 to .25. Some in the fenestration industry spoke out in support of disapproving, saying it would limit visible light and could compromise structural stability in certain applications. This victory, though, was followed with a bit of disappointment with the approval of EC34 and EC35, which will lower U-factors, and EC 41, which will lower SHGCs. Opponents say the lower U-factors will exclude metal-framed windows, creating a structural concern in some applications, while the lower SHGCs will limit visible light.

Looking at EC35 specifically, this proposal raised life safety concerns, in particular for coastal/hurricane-prone areas, as opponents say it does not account for heavier framing materials used in hurricane impact products.
“If you reduce the U-factor it would come at the expense of structural security … as the proposal would require products 30-35 percent weaker,” said Tom Culp, on behalf of the Glazing Industry Code Committee and the Aluminum Extruders Council. He added that it’s important to not ignore structure when looking at energy efficiency.

Thom Zaremba, speaking for Pilkington and AGC, also spoke against the motion. He said codes should always permit the use of the best possible products in applications, such as hurricane regions--which would be aluminum products.

“The energy code should not trump the best possible products in a severe region, such as a hurricane zone,” said Zaremba.

Also approved, EC41, as well as EC42 lower the SHGC to 0.25 in zones 1-3, and 0.40 in zone 4.  Skylights stay at 0.30 SHGC in zone 3. The concern by some surrounding the reduction to a 0.25 SHGC is that it will be restrictive on glass type and promote darker glass.  

EC36, which would have given some allowance to skylights to promote daylighting, was also disapproved. Julie Ruth for the American Architectural Manufacturers Association, spoke against the proposal.

“As the SHGC comes down it has an affect on visible light coming in,” she said. “If you lower the SHGC you can’t bring in efficient light … to have skylights benefit from the energy cost you need a somewhat higher SHGC.”
Though disapproved, her suggestion was creating a separate SHGC column for skylights on table 402.1.1, Insulation and Fenestration Requirements by Component.

Code hearings continue through Sunday in Charlotte, N.C. Stay tuned to USGNN.com™ for more reports and updates.

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