2004 Annual Interlaboratory Comparison of NFRC Accredited Testing Laboratories PDF

The National Fenestration Rating Council (NFRC) conducts annual Inter-Laboratory Comparisons (ILC) as part of its Laboratory Accreditation Program (LAP) for NFRC-accredited simulation and testing laboratories. This report presents the findings of the 2004 NFRC 102 Test Laboratory ILC of all seven NFRC-accredited testing laboratories.

Each participating laboratory conducted thermal performance tests on a 49 in. by 49 in. double pane skylight with a vinyl curb and aluminum retainer cap. The testing began in May and was completed in July of 2004. The thermal test data submissions from all the laboratories were reviewed, compared, and recalculated after errors were identified and corrected. Although all seven participating laboratories were within the two standard deviation tolerance of the average standardized thermal transmittance, detailed analysis showed that one laboratory incorrectly determined the projected area of the test specimen.

Upon recalculation of that laboratory’s standardized thermal transmittance using the correct test specimen area, the results from that laboratory could be considered an outlier. If that laboratory’s results are omitted from the recalculated analysis, the average standardized thermal transmittance from all of the laboratories is 0.44 Btu/(hr • Ft² • ºF) with a standard deviation of 0.013. This is identical to the standardized thermal transmittance that was derived from computer simulation by NFRC Staff using NFRC 100¹.

Presented at Thermal Performance of Exterior Envelopes of Whole Buildings X – December 2007

Units: Dual