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
“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
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
“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.
© Copyright 2009 Key Communications Inc. All rights reserved.
No reproduction of any type without expressed written permission.