NFRC Explores Daylighting Rating
December 15, 2010

Lisa Heschong of Heschong Mahone Group in Gold River, Calif., has done a great deal of research on the topic of windows and daylighting, a topic of great interest to the glass and glazing industry, and offered some input recently regarding whether or not the National Fenestration Rating Council (NFRC) should rate windows for daylighting. NFRC executive director Jim Benney tells™ that the organization developed a task group to explore this issue.

The task group was formed at the NFRC’s November meeting and Benney adds that the NFRC did identify daylighting as a potential new rating earlier this year. The task group is scheduled to come back with a recommendation in early 2011.

Benney says the NFRC is looking at two possible approaches.

“First of all, do we want to and can we develop a rating that rates daylighting?” asks Benney. “We have two paths we can take—a full blown model that looks at issues such as orientation, solar angle, etc.—all very complex issues. Or a simplified rating that is easier that merely helps the industry do a better job of communicating how much potential is in products.”

“Do we really need to look at complex variables?” adds Benney. “These are all issues we are looking at.”
As the NFRC had been looking at daylighting as a potential rating, the group asked Heschong to speak at its November meeting to offer additional details regarding the subject. On the pro side, she says visual comfort is to daylight as thermal comfort is to U-value; it is the next major policy push; and the NFRC has become the preferred source for window performance data.

On the con side, Heschong says it is too complex; there are too many secondary issues including view and privacy and it is a distraction from the core concern of energy; and finally, there are others who should do it.

Heschong also explained to attendees why there is so much attention from the industry on daylighting. “It is necessary to reach net-zero buildings,” she says. Additional reasons include reduced occupant complaints, sick building syndrome and increased tolerance for thermal swings and other acoustic annoyances.

She reported various studies that were conducted in retail, school and office environments that indicated that increased levels of daylighting lead to greater sales, faster learning and faster work speed than comparable spaces with less or no natural light.

Daylighting minimums are noted in ASHRAE and Title 24, says Heschong, as well as in the USGBC’s LEED program and the Insulating Glass Certification Council (IGCC) 2010. Looking ahead to 2014, Heschong reports that California is looking to require minimum daylit area for commercial buildings.

Daylighting is attracting the attention of not just code groups but manufacturers of windows, skylights, blinds and other products, as well as researchers, designers and others. In Heschong’s presentation she cited a “wish list” for the NFRC as it studies this issue which includes developing testing and reporting standards for daylighting products. This would include a type of public library of product performance data to enable evaluation of system level performance. She also suggests default values for generic products to be used in professional grade analysis tools.

“Ratings systems can come much later,” she says and are least important.

The NFRC will next meet March 28-30 in Las Vegas.

To offer your comments on the possibility of a rating system for daylighting contact Tara Taffera at or go to the™ message forum to express your view.

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