Low-e glass save energy. Normally, The single piece low-e glass's ( hard coated glass ) U-value is 2.8 w/m2k. Soft low-e coated double glass can be reached 1.75 w/m2k. If one low-e coated +12A + reflective coated. Then it can get lower U-value. For example: U-value=1.5w/m2k.