Rate of Heat Transfer through a product
U-Factor measures the rate of heat transfer through a product. Thus it’s rating indicates how well the window insulates. This measurement represents both heat loss during cold weather and heat gain during warm weather. U-Factor considers conductance, airflow, and the heat radiation or reflection of the glass. Values range from 0.20 to 1.20. Yes, window energy ratings seem confusing. But, remember that the lower the U-Factor, the better the insulation. Below is an example of a typical NFRC window label.
Energy Star U Factor Requirements
ENERGY STAR® qualified windows are independently tested and certified by testing procedures established by the NFRC (National Fenestration Rating Council.) U factor is one of the main components of an NFRC label. Below is ENERGY STAR’s minimum rating requirements for the various climate zones.
Harvey Windows U Factor
Harvey windows and doors qualify for ENERGY STAR because we are an ENERGY STAR Partner. Thus, our windows are independently tested and have NFRC ratings that meet (and exceed) the guidelines set by the U.S. Department of Energy. A window’s glass has the most significant effect on energy efficiency, and Harvey offers various window glass packages to meet your needs.
Additional Window Energy Efficiency
Window thermal ratings are not the only thing contributing to energy efficiency. Learn more about the other elements that make a window energy efficient. Also, our thermal performance guide provides data for Harvey windows and doors. This guide includes U-Factor, Solar Heat Gain Coefficient (SHGc), and Visible Transmittance (VT). Visit our ENERGY STAR page for further information about all of the performance categories.