GANA opposes proposed revision to ASHRAE 90.1

Sahely Mukerji
September 24, 2009
COMMERCIAL, RETAIL, FABRICATION

Officials at the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, are working on a revision to its standard 90.1 to increase building energy efficiency by 30 percent by 2030, and reduce the window-to-wall ratio on the prescriptive path to 30 percent from the current 40 percent maximum. This will limit the light to solar heat gain ratio for the prescriptive path in the standard, and provide designers with a set of tables with product value requirements to go through the energy modeling requirement for the performance path.

"GANA's members are on board with this goal, however, as an organization, we do not agree that the proposed method will achieve this goal," says Urmilla Jokhu-Sowell, director of glass and glazing industry standards, Glass Association of North America, Topeka, Kan. "ASHRAE's proposal has a minimum of 1.5 for center-of-glass VT/SHGC ratio, also called light-to-solar heat gain ratio or LSG. The glass industry does not believe this criterion will provide overall energy savings, but instead believes strongly more energy will be used."

GANA ASHRAE Subcommittee, led by Chair Helen Sanders, senior vice president of operations, Sage Electrochromics, Faribault, Minn., is working on educating ASHRAE's membership on the different types of glass products available, including high-performance and dynamic glasses, Jokhu-Sowell says. "GANA wants to make sure ASHRAE is aware that glass can help achieve this goal of a 30 percent overall energy savings through a combination of daylighting, high-performance glass and dynamic glazing technologies," she says. GANA sent a request to the ASHRAE 90.1 Committee to make a presentation to the members before they vote on the glass related issues.

Following is the list of concerns that GANA included in the latter to ASHRAE regarding the 90.1 proposal that will be voted on in October 2009.

  • The proposal precludes the use of many high performance glare control products currently on the market that offer moderate light transmission, such as spectrally selective tinted and coated products, which balance daylighting with glare control and solar heat gain. If the light transmission of the glass is too high, glare and non-uniform lighting (e.g. small bright areas adjacent to darker areas) will lead occupants to close blinds and/or turn on more task lighting, increasing lighting usage and therefore increasing energy use.
  • The proposal precludes the use of dynamic glazing solutions. Dynamic glass is a key energy savings technology and an important tool in achieving the zero energy buildings goal in 2030. The proposal, by providing a significant barrier to the adoption of dynamic glazing solutions, greatly increases the risk of not achieving that energy-savings goal unless additional interpretive language is added to the proposal.
  • The proposal fails to recognize the need for different glazing solutions across climate zones, particularly when viewed in combination with the proposed SHGC requirements. It is a “one size fits all” approach and will limit the glazing choices to a small range of high transmission, clear low-e glazing products. They may not be the appropriate products in all climate zones, particularly in the southern cooling dominated climates because of sunlight intensity. Use of such high transmission glass in those climate zones likely will result in greater use of blinds resulting in increasing lighting energy usage. Furthermore, in all climate zones, the high transmission contributes to visual and thermal discomfort and as a consequence to increased energy usage when occupants compensate with additional cooling resources.
  • A fixed VT/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 proposed requirement penalizes the glazing that provides more total light and does so in a more uniform manner with less need for blinds to control glare.
  • Even the slim possibility for saving energy in buildings is extremely limited unless the space also includes automatic daylighting controls. Recent proposals require daylighting controls only in rooms where the “primary side-lighted area” is greater than 1000 ft2. The room itself would likely have to be at least 1500-2000 ft2. The large majority of individual room sizes in buildings is well below this daylighting control threshold size; yet, this VT/SHGC is required in all spaces, even though there will be at best minimal or no energy savings.
  • Even if energy savings do result from the VT/SHGC proposal, those savings have not yet been quantified to determine whether they are significant enough to justify the elimination of a wide range of products from the market, potentially causing an anti-competitive impact in the marketplace. We believe the ASHRAE 90.1 Committee will find far greater energy savings simply by expanding the spaces where daylighting controls are implemented, rather than selecting certain glass types and eliminating others without adequate justification. In this regard, we offer to work with both the Envelope and the Lighting Subcommittees to develop a coordinated, mutually acceptable, technically sound proposal.