In a previous related blog, I spent some time discussing the important role that the AAMA/WDMA/CSA 101/I.S.2/A440 North American Fenestration Standard (NAFS) and our WDMA Hallmark Certification Program play in assuring that fenestration products meet the performance requirements and demands of the model building codes. In this post, I want to take you on a deeper dive to explain how certain performance requirements within the NAFS standard lead to quality products.
As designers know, fenestration products serve several multifunctional purposes: keeping the weather outside, allowing sunlight to illuminate the interior, prevent heat loss through the opening and allowing occupants to move in and out of the building.
To ensure they achieve these goals, windows, doors and skylights are subjected to a series of performance tests that determine their strength as well as their water and air resistance performance. The results of these tests determine the product classification category under which the product will fall.
The current version of NAFS has four basic “Product Classes” under which a fenestration product (excluding unit skylights, roof windows and tubular daylighting devices) can be classified:
AW
Commonly used in high-rise and mid-rise buildings to meet increased loading requirements and limits on deflection, and in buildings where frequent and extreme use of the fenestration products is expected.
LC
Commonly used in low-rise and mid-rise multi-family dwellings and other buildings where larger sizes and higher loading requirements are expected.
CW
Commonly used in low-rise and mid-rise buildings where larger sizes, higher loading requirements, limits on deflection and heavy use are expected.
R
Commonly used in one- and two-family dwellings.
To be classified in one of the above mentioned categories, the fenestration product must be tested at a certain size (known as Minimum Gateway Testing Size) and meet specific parameters for performance grade (PG), design pressure (DP) and structural test pressure (STP), along with certain air infiltration and water penetration resistance levels.
How does all this relate to high-quality window, doors and skylights?
While most consumers and designers may focus on the aesthetics of the fenestration product, builders, remodelers and architects know that the quality of the product is determined by its performance.
The NAFS document provides architects, builders and remodelers with the information needed to determine which product is appropriate for the project. Knowing the geographic wind speeds, building exposure and building height is key to specifying the appropriate Product Class and Performance Grade of the window, door or skylight from a structural performance perspective.
Air infiltration and water resistance also determine how the fenestration products will perform. For example, while a window with a certain design pressure may perform well from a structural standpoint in a coastal area by meeting the structural load requirements, the designer may want to consider specifying a higher performance grade to increase the water and air infiltration resistance performance.
Understanding label descriptions and how they relate to the product testing required in the NAFS standard is the first step to specifying high-quality windows, doors and skylights to complement your project.
To learn more about the NAFS and how it relates to product certification, be sure to visit our Learning Center and register for any one of the free webinars provided.
By: Steven Orlowski
Senior Director of Standards and Technical Activities for the Window & Door Manufacturers Association.
Webinar: Understanding Window, Door & Skylight Certification
Understand the benefits of window, door and skylight certification and how certified products can enhance your projects.
Webinar: Understanding Window, Door & Skylight Certification
The Understanding Window, Door & Skylight Certification webinar is designed to help architects and remodelers understand the benefits of window, door and skylight certification and how certified products can enhance their projects.
