NFRC Technical Committee Sends New Information to Its Task Groups
July 20, 2010

The National Fenestration Rating Council’s (NFRC) “virtual meeting” continued yesterday with a review of several ballots at the start of the Technical Committee’s meeting.

The Solar Heat Gain Subcommittee reviewed a ballot on NFRC 200 section 4.5G Laminates. According to NFRC, the ballot is intended to clarify language in the section as it relates to laminated glazing in the matrix of center-of-glazing SHGC/VT options.

The group discussed a negative submitted by John Gant of Glen Raven, who had commented, “It seems that the phrase ‘ratings for products with obscured, frit or wired glass and/or stained glass shall be deemed to be equivalent to the ratings for clear glass’ should be deleted in its entirety since WINDOW6 can model these variations to provide more accurate VT ratings.”

Dennis Anderson, NFRC liaison to the group, explained that the task group had intended only to slightly modify a sentence that had existed for several years by adding the word “frit.”

Mike Thoman of Architectural Testing pointed out, “What WINDOW6 can or cannot do as of today is irrelevant because it’s not an approved software for us to use. At this point in time this provision has been in use for years, it’s not the time for us to address this.” Thoman added, “I do believe it’s legitimate to discuss it when WINDOW6 is approved,” pointing out that the new software could lead to further changes for the group.

The negative ultimately was withdrawn so that the group could discuss the approved ballot further in the full meeting of the technical committee.

The group next discussed negatives on a ballot on a revised draft of NFRC 201. According to information from NFRC, the updated draft adds the capability to measure the SHGC of tubular daylighting devices (TDD) in solar calorimeters and specifics of how to do so in annex G2.

Annex G2.3 proposed that “the cross-sectional area of the exterior of the tube shall be used to calculate the SHGC.” A negative on this section stated, “The incident light needs to be more accurately assessed to avoid significantly overstating the resulting SHGC.

Using the tube dimensions to determine Asub-s ignores the typically much larger exposed ‘footprint’ that actually receives the incident solar heat.”

Willie duPont of Sunergy Consulting, in a motion to consider the negative persuasive, noted, “This would be proposing a change in how we evaluate SHGC in its most basic terms …”

The group agreed more discussion was needed and a vote decided the ballot would be returned to the task group. The group continued to the next negative, though, for which duPont commented, “I don’t have an easy solution for this.”

His concern was that tests are done at a 30 degree incidence to the sun.

His negative response added some language that would require: “The TDD shall be installed in a 30.0-inch-thick surround panel with an aperture of sufficient size to accommodate the TDD. The Flanking Loss of the surround panel shall be determined as specified in Annex C. The entire perimeter edge of the surround panel must fit within the aperture of the solar calorimeter (i.e. within the control volume) so that the outer face of the surround panel is flush with the outer face of the solar calorimeter.

“I’m not entirely convinced that’s accurate or possible using the flanking loss," DuPont said. “These off-normal tests are a new phenomenon to NFRC and a lot of thought needs to be put into them,” duPont said.

Given that the group had already voted to return the ballot to the task group, this item, too, was added to the list for further discussion.

Yesterday’s other technical committee subcommittee meetings went quickly. The Air Leakage subcommittee breezed through its meeting, with little new to report since the April meeting in New Orleans (CLICK HERE for related story). The U-Factor Subcommittee heard reports from several task groups, with little new to add beyond goals for the future.

Dave DeBlock of ODL Inc. said that the Tubular Daylighting Devices task group is “continuing to work on visible transmittance … it’s a goal to get something for the NFRC label as soon as we can.”

Dennis Anderson, liaison for the Door task group, noted that this group continues to work on a benchmark spreadsheet on area weighting of doors, primarily entry doors, for simulations. The group currently is waiting on information from simulation labs.

DeBlock added, “We are also looking to eventually take what we learned if that spreadsheet can be put into the simulation software we may at some point be able to load door glass assemblies … to make that a simpler way to get that done.” It was quickly added that this goal would be a second phase of the project somewhere in the future.

During the report from the Sightline Tolerance Task Group, chair Joe Hayden of Pella explained, “This task group was formed last time to explore how we can better, more effectively group products that have a large number of sightline variations within a given offering quickly.” While Hayden says the group has nothing to bring forward just yet, he added, “The concept we’re zeroing in on is the idea of still grouping these products by U-factor as we always have done” but now looking to “possibly create a standardized offset from center of glass heat gain and VT based on the frame area.”

The NFRC’s meetings continue this afternoon and run through the board meeting on Wednesday. Stay tuned to USGNN.com™ for more meeting reports.

CLICK HERE to read yesterday’s USGNN.com report on the meeting.

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