Phase I Results of the NFRC U-Value Procedure Validation Project

The NFRC U-Value Procedure Validation Project was undertaken by a collaborative group of industry, public utility, trade associations, and government researchers in order to validate the testing and calculational methods of the NFRC 100-91: Procedure for Determining Fenestration Product Thermal Properties (Currently Limited to U-Values). This paper summarizes the validation projects goals and test methodology, the results of the data analysis, and the recommendations following 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 100% of the cases. Window test results with perpendicular wind 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 test 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 improve as a result of a strong NFRC education and accreditation program.