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Are there ENERGY STAR certified Glass Block Windows? Follow

Factory-built glass block windows are eligible for the ENERGY STAR, but most glass block windows are built onsite. If you are purchasing glass block windows, look for the ENERGY STAR label to determine if the product is qualified. If the window is being assembled onsite using individual glass blocks, it is not eligible for the ENERGY STAR because it has not been tested and certified by the National Fenestration Rating Council (NFRC). All ENERGY STAR qualified windows, doors, and skylights must be tested and certified by NFRC.

More on ENERGY STAR qualified windows.

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