In order to calculate glazing performance values, the primary requirement within the NCC 2019 – Vol 1 is to meet the definitions within Schedule 3 through a recognised repeatable calculation methodology and provide evidence to support compliance with a relevant ABCB protocol. There is no ABCB protocol for this subject matter.
The Window Energy Rating Scheme (WERS) provides a rating system for the assessment of glazing performance and state to be compliant with the NCC 2019 – Vol 1. To date, the commercial glazing industry has not traditionally used WERS values when considering the overall performance of glazing systems as the market has identified multiple reasons that justify commercial glazing not adopting WERS values.
As the WERS rating system only aims to compare one glazing system at a specific size against another, it does not provide the performance values required for the optimisation of a commercial building envelope where calculation accuracy is required. In addition, WERS values typically exclude subframes thermal losses while its supporting AFRC methodology is not a recognised Standard. A such, published WERS data typically ignore subframe thermal losses while suppliers are unlikely to include them as they create a lower performance value and an unfair comparison.
Therefore, any data provided online data or embedded within software are likely to not meet NCC 2019 – Vol 1 requirements if the performance requirement includes the assumption that an accurate representation of a glazing system is required. Speckel uses an alternative method (ISO 15099: 2003 4.1.4) for calculating frame thermal transmittance.