Window U-Factor and SHGC

This is of interest to anyone working on LEED Projects outside of continental USA where there is no NFRC rated fenestration ? In our case the window frames are from France and are certified according to " ISO / EN Standard 10077 - Thermal performance of windows, doors and shutters " Would this ISO standard be an acceptable alternative to NFRC certification ? Or do we have to use Window or CMAST to calculate according to NFRC ?

Yes, Mike, a great question, and not about windows only ! Mandatory provisions in ASHRAE, i.e. in 5 section mostly are about labelling and approved measure methods for different products/constructions. How to comply with requirements, i.e. about labelling, outside US??

During LEED reviews the labeling requirements in 90.1 are not strictly enforsed. The window performance values are scrutenized based on an expected range of performance given the specific window type. For example, if a wood framed window with double glazing was outside a U-factor of 0.31 to 0.36 or so then the U-factor may be questioned. The label is only needed if the product is reported to be performing outside an expected range. In those cases a detailed description on the window framing and glazing may be needed. A local certification like the ISO/EN Standard is typically fine. A Windows 5 run would also likely suffice. So without a NFRC label simply document how the window performance values were determined. The values in A8,2 are very high and can be used without question but as pointed out will likely be worse than the baseline.

Thanks - i have recently seen a ruling allowing the admission of fenestration rated by the Japanese authorities. I guess then that any fenestration rates according to an ISO standard would, as you note, be acceptable with supporting documentation.