RDH Building Science

The introduction of the North American Fenestration Standard (NAFS) to Canadian building codes presented architects and other registered professionals with a new way to specify, test, and rate the structural-air-water properties of windows, doors,
and skylights. Known in the building code as the Harmonized Standard, NAFS was intended to harmonize Canadian and American performance testing and ratings standards to facilitate cross-border trade in fenestration products. While most issues were harmonized, significant differences remain between how NAFS is implemented under Canadian codes and how NAFS is utilized in the US. In Canada, NAFS is referenced in Part 5 and Part 9 of the code, always in tandem with a document known as the Canadian Supplement to NAFS. Taken together, these documents are intended to help builders and building designers ensure that fenestration products effectively resist the environmental loads specific to each building in its geographic location.

With the title “North American Fenestration Standard,” it is tempting to think that NAFS applies equally to all fenestration products and that it is the single reference for addressing their structural-air-water properties; however, this is not the case. While NAFS applies to a great many fenestration products, it excludes from its scope many products used in larger buildings. Fortunately, the code recognizes this and provides complementary compliance paths for products within and outside the scope of the standard.

This guide clarifies the intended use of NAFS for the products within its scope, and provides building designers with a rational methodology for specifying the structural-air-water properties of fenestration products in Canada. All code references hereafter are to the 2010 National Building Code, except where noted.


RDH Building Science