The introduction of the NAFS standard in the 2012 BC Building Code has changed how we specify fenestration performance in BC. Together with the NAFS standard it mandated use of CSA A440S1-09, the Canadian Supplement to NAFS, instructing Code users to use the Supplement to determine the appropriate fenestration performance grades (design pressure and water penetration resistance) for a particular building’s location and terrain.
Most users of the Code are not aware of the limitations of the supplement, however, nor are they aware that its definitions of open and rough terrain do not correspond to those in the Code. In addition, the Part 5 code language that refers to NAFS and the Supplement, taken from the 2010 NBCC, does not reflect the role played by professional engineers in ensuring fenestration systems meet the Code’s structural requirements under BC Letters of Assurance.
To rectify these issues the Technical Committee of the Fenestration Association of BC issued this technical bulletin on January 27, 2014. In addition to correcting terrain definitions, it addresses the appropriate use and limitations of the Canadian Supplement. It concludes with recommendations for using the Supplement on Part 9 and Part 3 buildings. The Part 3 recommendations are particularly relevant to architects who are directed by the Code to use the Supplement to determine fenestration performance grades.