Incorrect Performance Values Being Used
Many energy ratings, particularly those entered into the free on line calculators are using glass only U Value (U GLASS) and Solar Heat Gain Coefficient (SHGC GLASS) performance results.
Not using total window system values to Australian approved procedures and environmental conditions can result in significant under performance or over performance of the building envelope, especially in buildings with large glazed areas. The stated performance of the building will not meet the energy efficiency provisions of the BCA.
Read full article by Australian Window Association (AWA).