Volume 44, Issue 11 - November 2009


Glass Industry Gains Compromise from ASHRAE on Glass Use in 2010 Update

Several compromises were reached between the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Envelope Subcommittee and members of the glass industry during a meeting that took place in early October on the 2010 revisions to Standard 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings.

ASHRAE’s Envelope Subcommittee had earlier this year proposed revisions to the 2010 edition of its 90.1 standard that would, among other things, reduce the window to wall ratio and greatly limit the light to solar heat gain (LSG) ratio for the prescriptive path in the standard. The prescriptive path is based on a three-story office building and would provide a set of tables with product value requirements for designers who don’t wish to go through the energy modeling required for the performance path.

According to Helen Sanders, chair of the Glass Association of North America’s (GANA) ASHRAE Subcommittee, the proposal had included a requirement that the glazing of the window system must have a LSG ratio of greater than 1.5, based on center of glass, or greater than 1.3 if based on the whole window.

“What they’re trying to do is come up with a very simple approach for code officials, but it’s being so simplified that it likely won’t provide the energy savings that they are seeking,” Sanders says, adding, “and it will at the same time exclude a lot of very good, high performing products from the market.”

During the October meeting Stanley Yee of the Façade Group made a presentation to the ASHRAE Envelope Subcommittee on behalf of GANA’s ASHRAE Subcommittee. “The main message of the presentation was essentially that the LSG criteria of greater than 1.5 essentially eliminated the possibility of using up to 60 percent of the high-performance glass products that are available on the market today,” Yee explains.

The GANA presentation also pointed out that mandating LSG of greater than 1.5 could result in the misapplication of glass in the absence of considering significant environmental factors such as orientation and climate zone.

Another cause of concern for the GANA group was that there has been no definition for dynamic glazing in the proposed updates of the ASHRAE standard. “Inadvertently, the proposal had basically eliminated the possibility of using dynamic glazing, which to the [GANA] group was rather intriguing considering that the Department of Energy has conceptually acknowledged that it is a step in the right direction as far as technology goes and trying to achieve net zero-energy,” Yee says.

In the end, some compromises were reached.

“The end result was that they had reduced the 1.5 criteria to 1.25, center of glass,” Yee says. In addition, the Envelope Subcommittee also opted to create a new track for outlining information specifically on dynamic glazing.

Yee is reluctant to call the compromise an outright victory, “Because,” he says, “we haven’t really assessed fully what the implications will be of what we’ve landed on.”

Moreover, the ASHRAE Envelope Subcommittee made some new changes to the performance path in the proposed standard updates.

“What we’re talking about is the prescriptive path, which is what probably 80 percent of the projects that get built in this country are based on,” Yee says. “[For] the 20 percent on the performance path, or what’s sometimes called the trade-off path, they increased the requirement. It used to be the same requirement as the prescriptive path.”

Sanders explains the implication of these changes: “ASHRAE 90.1 is not a code, it’s a standard, but a number of different cities and states have adopted ASHRAE 90.1 as their energy code—so although it’s a standard it is a critically important standard because it basically affects code across the U.S.”

“This is an example of why it is important that the glazing industry stay actively involved,” adds Tom Culp of Birch Point Consulting. “During these rough economic times, it is tempting to reduce external focus and only worry about business essentials, but that is a profound mistake. I’ve never seen such intense pressure to increase energy efficiency standards. While this can create opportunities for value-added products and building integrated photovoltaics, there is
also the danger that irrational or technically flawed requirements are

Representatives from GANA, Guardian Glass, PPG Industries, AGC Flat Glass and Pilkington North America attended the meeting. GANA encourages other industry professionals to watch for the second round of public review of the standard, anticipated in January.

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