Glass strength design under NBC 2015/2020 and use of CSA A440S1 to determine Part 9 glass design pressures for use with CAN/CGSB-12.20-M or ASTM E1300



The 2015 NBC made two significant changes affecting calculation of wind loads for glass design. The first was to reduce the factored hourly wind pressure by 25% when designing glass to CAN/CGSB-12.20-M. The second was to allow the use of ASTM E1300 for glass design. Both changes were accomplished by the introduction of a ”wind load adjustment factor” in Article


This bulletin describes the changes to the design basis for glass introduced in the 2015 NBC and present in the 2020 edition. It also describes how serviceability limit states (SLS) wind pressures determined using CSA A440S1 to determine design pressures for selecting NAFS Performance Grades can be converted to ultimate limit states (ULS) pressures for glass design by using the appropriate importance factors