Industry Raises Concerns Over ASHRAE 90.1 Revisions That Could Reduce
the Use of Glass in Nonresidential Buildings
September 21, 2009
The American Society of Heating, Refrigerating, and Air-Conditioning
Engineers (ASHRAE) is working to revise its standard 90.1, Energy
Standard for Buildings Except Low-Rise Residential Buildings
- with potentially huge impact to the glass industry.
According to information from the Glass Association of North America's
(GANA) new ASHRAE Subcommittee, which met at GANA's Fall Conference
earlier this month, ASHRAE's Envelope Subcommittee has proposed
revisions to the 2010 edition of its 90.1 standard that would reduce
the window to wall ratio and greatly limit the light to solar heat
gain ratio for the prescriptive path in the standard. The prescriptive
path, based on a three-story office building, 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
"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.,"
says Helen Sanders, chair of GANA's ASHRAE Subcommittee.
According to Sanders, the proposal includes a new requirement that
the glazing of the window system must have a light to solar heat
gain (LSG) ratio of greater than 1.5, based on center of glass,
or greater than 1.3 if based on the whole window. In addition, the
revised standard would reduce the window to wall ratio from 40 percent
down to 30 percent as well as lowering the maximum SHGC allowed
in each climate zone.
Sanders explains that the GANA Subcommittee is opposing the LSG
revision in particular because the group is concerned that a "one
size fits all" requirement will lead to higher visible light
transmitting (VLT) products in inappropriate climates zones where
no actual energy savings will be provided.
"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."
Among the GANA Subcommittee's concerns are:
- The proposal does not recognize or accommodate the need for
different glazing solutions across climate zones. It is a "one
size fits all" approach and will limit the glazing choice
to a small range of high transmission, clear low-E glazings. They
are not the appropriate products in all climate zones, especially
the Southern cooling-dominated climates because of the sunlight
intensity. Use of such high transmission glass in those climate
zones will likely result in greater use of blinds resulting in
increasing lighting energy usage.
- A fixed VLT/SHGC ratio as proposed does not account for the
fact that a large darker piece of glazing actually admits more
light than a small clearer piece of glazing. This requirement
penalizes the glazing that is providing more total light and is
doing so in a more uniform manner with less need for blinds to
- There is only limited possibility for saving energy in buildings
unless the space also includes automatic daylighting controls.
Even with recent proposals, daylighting controls are only required
in rooms where the "primary side-lighted area" is less
than 1,000 square feet. The room itself would likely have to be
at least great than 1,500 to 2,000 square feet. The large majority
of individual room sizes in buildings are well below this daylighting
control threshold size; yet this VLT/SHGC is required in all spaces,
even though there will be minimal energy savings.
Sanders adds, "If there are any energy savings as a result
of this VLT/SHGC proposal, the savings have not yet been quantified
to see if they are significant enough to justify eliminating a wide
range of products and causing a potential anti-competitive impact
in the marketplace."
"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 created. This proposed change involving VT/SHGC is one example
where it would harm more than 50 percent of commercial glazing products-yet
without any energy savings in most cases. There are much better
ways to promote energy savings and daylighting, but we need more
than just one or two voices to make our case in these forums. It
has been rewarding to see the glazing industry come together to
address this issue under GANA, and I hope it continues."
GANA's ASHRAE Subcommittee is working to send alternative proposals
and guidance to ASHRAE that would prevent the drastic change, and
will reiterate its concerns at a meeting on the standard at ASHRAE's
headquarters October 1-3.
"GANA, through its Energy Committee has a working group that
is focused on ASHRAE 90.1 Committee's work, especially the Envelope
Subcommittee," explains Urmilla Jokhu-Sowell, P.E., GANA's
director of glass and glazing industry standards. "GANA's ASHRAE
Subcommittee is working on educating ASHRAE's membership about high-performance
glass and the different types of glass products available. ASHRAE
is working on a goal of increasing energy efficiency by 30 percent
by 2030. GANA wants to make sure ASHRAE is aware that glass can
help achieve this goal through daylighting, high-performance glass
and dynamic glazing technologies."
Sanders encourages members of the glass industry to prepare for
the second round of public comments to the standard, which is expected
to be available in late October.
to offer your comments on the proposed changes to ASHRAE 90.1.
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