Incorrect Use of Glass Only Values for Glazing Energy Performance Ratings

Through our relationship with the Australian Window Association (AWA), Viridian has been made aware that last week three South Australian window companies advised energy raters to use Glass only U-values (UGLASS, UCOG, UG) and SHGC (SHGCGLASS, SHGCCOG, SHGCG) in the absence of immediately available window (glazing) results to carry out building performance ratings.

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. Under the National Construction Code (NCC), within Building Code of Australia (BCA), energy efficiency provisions for Volume One, Section J2.4 Glazing and Volume Two, Section 3.12.2.1 External Glazing state that external glazing performance data must be determined in accordance with the guidelines of the AFRC (Australian Fenestration Rating Council).

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.

Learn more about this industry alert through the Australian Window Association.