The NatHERS Administrator has released a guidance note on the use of custom windows which can be downloaded from the NatHERS website. The guidance note reads as follows:

"Guidance Note 1: Custom Windows
Guidance for treatment of window value discrepancies between the custom windows library and Window Energy Rating Scheme (WERS)

Effective from 27 July 2017 (for use with software using Chenath Engine V3.13)

Where a custom window has been selected in Nationwide House Energy Rating Scheme (NatHERS) accredited software tools and there is a discrepancy in the stated U-value and/or Solar Heat Gain Coefficient (SHGC) to the corresponding Window Energy Rating Scheme (WERS) data of less than 10%, and ALL of the following are the same:

• the window manufacturer
• window type (e.g awning, sliding, casement)
• frame type (e.g timber, aluminium)
• glazing type (e.g clear, single glazed, double glazed low e)

then the window is considered the same for compliance purposes.

Any variations in windows that fall outside the bounds outlined in this Guidance Note should be raised directly with the Australian Fenestration Rating Council (AFRC), and copied to the NatHERS Administrator."

Contact details are as follows:
AFRC: [email protected] and [email protected]
NatHERS: [email protected]