What is considered a thermally improved aluminium window frame?
An aluminium improved frame is defined as one with a U-value of 8.0 W/m2.K or less. This may be achieved by a variety of design improvements, some (or all) of which may be present. Examples include exterior or interior trim made of wood of plastic and attached by clips or adhesives. It is not reliable to estimates the effectiveness of such measures by appearance alone; therefore a U-value of 8 or less, derived from a WERS rating, shall be the sole criterion for classifying a window as ‘thermally improved’.
An aluminium improved frame is defined as one which is broken but has a gap of less than 5.30mm between the pieces of aluminium. This may be achieved by a variety of design improvements, some (or all) of which may be present. To be classified as broken, a window must conform to the following definition by the U.S. National Fenestration Rating Council (ref: NFRC 100-2001).
