The NFRC U-value Procedure Validation Project was undertaken by a collaborative group in order to validate the testing and calculational methods of NFRC Standard 100-91, Procedure for Determining Fenestration Product Thermal Properties (Currently limited to U-values). Summarised the validation product's goals and test methodology, the results of the data analysis, and the recommendations following the completion of phase I of the project. Simulations performed according to NFRC 100-91 are shown to agree with each other to within the NFRC tolerance in 84% of the cases. Simulations and perpendicular wind window tests results are shown to agree with each other to within the NFRC tolerance in 80% of the cases. Testing of skylights was shown to be problematic under the procedure as written at the time. Agreement between tests and simulations will, it is said, improve as a result of a strong NFRC education and accreditation program. NFRC = National Fenestration Rating Council.

KEYWORDS: Windows, computer programs, calculating, validating, thermal insulation, heat loss, glazing, standards, USA.