Closer look: ASHRAE 189.1 to spur use of more high-performance products

New green building standard will require triple glazing in northern climate zones
Sahely Mukerji
March 25, 2010
FABRICATION : CLOSER LOOK

After a three-year development process, in February, the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Atlanta, approved and published ASHRAE 189.1, the first code-enforceable green building standard in the nation.

The new standard covers all commercial buildings, as well as residential buildings four stories and higher. “It is not intended to be the minimum energy code like ASHRAE 90.1 [Energy Standard for Buildings Except Low-Rise Residential Buildings], but goes further to include both a higher level of energy performance as well as green attributes similar to LEED [Leadership in Energy and Environmental Design],” says Thomas Culp, president, Birch Point Consulting LLC, La Crosse, Wis. Unlike LEED, it is written in mandatory language like a code--rather than a point system--so that local jurisdictions can adopt it as an advanced code if they wish. “For instance, I expect some jurisdictions will use ASHRAE 90.1 as their base standard for private buildings, but require ASHRAE 189.1 for publicly funded buildings,” he says. “They could also provide incentives such as tax credits or expedited permitting if ASHRAE 189.1 is used for private buildings.”

The standard could be referenced on a project-specific basis by architects who are interested in designing high-performance green buildings, says Greg McKenna, chief product engineer, Kawneer Co., Norcross, Ga.

“ASHRAE 189 is the start of a new generation in commercial glazing which will incorporate more coated glass products,” says Jon Hughes, director, Technical Services, AGC Flat Glass North America, Alpharetta, Ga. “Low-E penetration in the commercial sector is a fraction of what it is in the residential sector; the industry will see more low-E coated glass utilized in Zones 5 through 8.”

Effects on glass and framing

There are many aspects of ASHRAE 189.1 that will affect the glass and glazing industry, Culp says. It includes aggressive U-factor and solar heat gain coefficient criteria. “This will increase the use of low-E glass, good thermally broken frames, warm-edge spacers and argon,” he says. “It will also require triple glazing in northern climate zones, and perhaps even in the middle of the country for heavy commercial products. All this can be done, although concerns have been raised whether all fabricators and installers are ready for triple glazing on more than a custom basis.”

For the building envelope, the standard calls for increases in thermal performance for curtain wall and windows from 15 percent in the southern climate zones to as much as 25 percent in the northern zones, McKenna says. “This will lead designers of these products to look for better ways to insulate their frames to help drive U-factors lower,” he says. “In climate zones 1-5, (on the east, south and west elevations) the standard also calls for minimum projections over windows that are as deep as 50 percent of the window height. The intent is to shade the glass to reduce the amount of direct solar radiation on the glazing. This could encourage building designs to have deeper recessed window openings or curtain walls that incorporate integral sunshades.”

Increases in thermal performance will require glass fabricators to continue to look for ways to lower their center-of-glass U-factors, McKenna says. “Modern low-E coatings coupled with inert gas fills in insulating glass have kept up with the building codes to this point; but ASHRAE 189.1 will push the envelope,” he says. “In climate zones 7 and 8, triple glazing will often be required to meet the very low U-factors. Wider use of warm-edge spacers will also help to lower overall U-factors.”

Triple glazing will add design and handling issues for both architects and the glazing industry, says Steve Farrar, director of International Business, Guardian Industries, Auburn Hills, Mich. “However, with or without ASHRAE 189, triple glazing appears to be coming to the northern parts of the country as the Department of Energy continues to push for an R-5 (U-0.20) window.” ASHRAE 189 would require more triple glazing in zone 5 and above, he says. This would include several population centers such as Boston, Pittsburgh, Chicago, Minneapolis and Buffalo.

Triple glazing could be the path to success for many industry professionals, Hughes says. “ASHRAE 189.1 introduces triple glazing to the prescriptive path in the North,” he says. “To the glazing professional, this means an opportunity to differentiate themselves by establishing a competitive advantage. Triple pane -- as higher performance products are required, the industry will have the same growing pains as when it moved from monolithic to double glazing. All factors will need to be considered, from product design to performance, durability, fabrication and installation concerns. These new complexities will create unique competitive advantages for companies willing to embrace these challenges.”

In addition, framing products that have extremely strong thermal-resistant properties will be required, and they will have to accept higher performance glazing, including triple glazed units, in order to meet these stringent codes, says Mike Turner, vice president of marketing, YKK-AP America, Austell, Ga. “Many design attributes may also have to change. An example of this would be center-set storefront. The design community may have to embrace more front-set products to meet the ASHRAE 189 prescriptive standards.”

Glass and glazing professionals will have to become more familiar with how the framing and glazing systems perform together, Turner says. “YKK AP has simplified this process by utilizing the AAMA 507 reporting system. This system utilizes [National Fenestration Rating Council] test methods and provides a matrix of total system performance values when using a variety of glazing types. It allows the glass and glazing professionals, and designers the ability to see the overall system's performance values prior to specifying or bidding a project. This tool will prove to be very useful to ensure products meet the project's requirements at bid time.”

The initial effect of the standard will be high project costs because of more high-performance product requirements, Turner says. “As these products become more readily available and production volumes increase, the costs should begin to come down. But the current impact is that the initial projects will cost more.”

Influence on solar glazing

ASHRAE 189.1 does not directly require on-site renewable energy systems like photovoltaics, but does include strong incentives and that the building provide the infrastructure for future installation of these systems, Culp says. “This will help support the growth of our solar glazing industry.”

The standard strongly promotes daylighting. It requires a minimum skylight area and daylighting controls on large open spaces, such as big box retail and warehouses. It also requires a minimum “effective aperture” for glazing in offices and schools, which can be met by either higher VT products or increasing glazing area, Culp says. “They also keep the prescriptive glazing area limit at 40 percent, partially in recognition of the benefits of glazing for daylighting,” he says. “This is the opposite of the battle we have been fighting at ASHRAE 90.1, which is trying to reduce the glazing limit to 30 percent under the false impression that ‘windows are really just a bad wall’ when you mistakenly only look at R-value.”

The standard takes a more direct and rational approach to fenestration standards than does ASHRAE 90.1, Farrar says. “For example, it avoids arbitrary minimums for the light-to-solar-gain ratio, emphasizing instead building design such as shading projections on the west, east and south exposures. Also, it keeps the maximum window-to-wall ratio at 40 percent, while ASHRAE 90.1 would reduce it to 30 percent.”

“Although I may not agree with every requirement and I do not think ASHRAE 189.1 should be the norm for every building, I view it as a good step forward for green standards,” Culp says. “It is ‘tough but fair’ for a high-performance standard.”
 

E-mail Sahely Mukerji, senior editor, at smukerji@glass.org.