Is it time to develop fenestration daylighting ratings?
Daylighting gets a lot of attention in green building circles these days,and deservingly so. Studies have shown that increased daylighting levels provide benefits such as reduced absenteeism in schools, increased worker productivity, faster healing in hospitals, increased spending in stores, and more. Who doesn’t desire an office with a window; or even greater – the corner office? We all would rather read the morning paper under the light of day, than the harsh light of fluorescence. There is even a proven mood change due to the lack of natural light: Seasonal Affective Disorder.
Of course, many of these benefits cannot be measured. The one attribute that can be quantified is energy savings. Providing independent and accurate daylighting ratings would offer a more complete picture of fenestration’s role in buildings, particularly its effect on reducing electricity consumption associated with indoor lighting.
NFRC’s Daylighting Rating Task Group held its first in-person meeting last fall in San Francisco. The task group’s scope is to create a rating system for daylighting potential using the existing NFRC visible transmittance rating combined with known, bright day incident illuminance values. The task group formed a working group to explore bright sky illuminance and to determine the best way to begin developing a rating.
The working group’s first assignment is to determine the type of sky needed to use in developing the rating, i.e., clear or diffuse. The working group is expected to present its recommendations at NFRC’s Spring 2011 Committee Week in Las Vegas, which will take place March 28-30.
The daylighting rating effort is in a preliminary stage. At this time, NFRC is exploring how to proceed. If NFRC pursues daylighting ratings, we will need to decide whether to create a complex model that takes into account the angle of the sun, orientation of the building, and other factors, or a simpler method that measures daylighting potential. Then, decisions would need to be made about whether to use an index or letter rating system, whether to integrate it with visible transmittance, etc.
It can take years to develop new rating procedures, and it requires the input of all interested stakeholders to ensure those procedures will be independent and credible. We invite you to learn more about NFRC’s exploration of daylighting ratings and to participate in the process.
--Jim Benney is the National Fenestration Rating Council’s chief executive officer. He has been involved in developing product and performance standards for the window and glass industry for more than 25 years. He can be reached at firstname.lastname@example.org.
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