Glass 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 path.

"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 control glare.
• 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.

CLICK HERE to offer your comments on the proposed changes to ASHRAE 90.1.

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