Pub. 2 2021-2022 Issue 1

26 REFLEXION | 2021-22 | AIA Utah W hen professionals select windows or doors for use in buildings, they need to know how those windows will perform under hazardous weather conditions. The performance grade (PG) rating and the design pressure (DP) rating are useful tools to help architects select a project’s windows. An architect can use them to decide on the most appropriate window choices for a particular project. PG ratings and DP ratings are not equivalent. For example, the DP rating is simpler than the PG rating. The DP rating is only concerned with whether a product can withstand uniform loads caused by wind or (in the case of skylights) snow. The PG rating is given to products that meet the industry standard’s performance requirements. AAMA/WDMA/CSA 101/I.S.2/A440-17, the North American Fenestration Standard, is commonly referred to as NAFS-17. It has four mandatory performance requirements: • Resistance to air infiltration • Resistance to water leakage • Structural adequacy to withstand wind loads • Resistance to forced entry In addition to the performance requirements, auxiliary product- specific tests are done. The test results determine the single structural class rating. The air, water and wind load tests indicate how much wind, water and structural load a window or door can withstand without failure. PG and DP Window Ratings: An Interview with Brent Mangum, Amsco Windows