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The negative ultimately was withdrawn so that the group could discuss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
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
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
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
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
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
HERE for related story). The U-Factor Subcommittee heard reports
from several task groups, with little new to add beyond goals for
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
HERE to read yesterday’s USGNN.com report on the meeting.
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