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The question I receive frequently is; who makes the best window? When the question should be; what is the best product for my specific application under the various environment conditions the building will be exposed to? As an architectural specifier, fenestration details can make or break your project. This article will further the practical understanding and use of window, door and skylight standards for product performance ratings. With an increased focus on everything from product performance for weather events to energy performance, windows doors and skylights matter in the performance and occupant experience of the built environment. Many factors should be considered when choosing the proper products for the design for a specific application or geographic region. A review of the relevant industry standards for the performance related to air infiltration, resistance to water penetration, structural performance, resistance to wind borne debris as well as several factors affecting the energy performance of products will be discussed. This article will further the understanding of high performance windows, doors and skylights. This article will also address the linkage between the exterior fenestration standards, the building code requirements and viable certification programs that provide affirmation of compliance to the building code and specification requirements.

Standards development is a dynamic process and the current standards took years of development working with the many interest groups.

The North American Fenestration Standard (NAFS), for windows doors and skylights, was developed over decades of work and included the harmonization of standards from the United States and Canada. The WDMA standards and test methods are referenced in building codes, are required by architectural and builder specifications, and form the basis for high performing, relevant product ratings. The documents referenced in the building code include the wind design criteria and structural wind load requirements as well as air infiltration, resistance to water penetration, materials and component performance requirements. The building code also requires protection of openings by impact resistance to wind borne debris in coastal regions susceptible to hurricanes. The building code also includes specifics on fenestration testing and labeling. The most recent version of the standard is the “North American Fenestration Standard/Specification for Windows, Doors, and Skylights, AAMA/WDMA/CSA 101/1.S.2/A440-17” or (NAFS).

NAFS

To achieve a rating to the NAFS standard, a product must be evaluated for compliance to the following performance requirements: structural loading, resistance to water penetration, air leakage, operational force, forced entry resistance, as well as the standards performance and prescriptive requirements for materials, components that are incorporated into the completed fenestration product. This standard is the primary linkage between standards, building codes and certification for these performance attributes.

NFRC

The building code requirements for Energy Labeling reference the National Fenestration Rating Council (NFRC) standards. The NFRC was founded in 1989 to create a uniform method for the energy performance ratings of window, door and skylight products and NFRC’s role as the nation’s organization for rating the energy performance of fenestration products was codified by the 1992 with the Energy Policy Act. NFRC is the leader for ensuring the fair and accurate energy ratings of fenestration products. There are several factors that go into the energy performance of fenestration products and the most apparent property for the thermodynamics of a system is the temperature driven heat transfer measured as a U-factor.  U factor measures the heat transfer under winter night time conditions. Additional ratings for solar heat gain and air infiltration are also required by the building code. The lower the U-factor, the better a product is at keeping heat inside the building. The NFRC U-Factor Ratings are based on winter night time conditions of exterior 0 degrees and interior 70 degrees Fahrenheit. The Solar Heat Gain Coefficient (SHGC) is the measure of the heat gained through fenestration products by direct or indirect solar radiation. The lower the SHGC number, the lower solar heat gain. Additional information on NFRC ratings can be found at www.nfrc.com. Selecting a low U-factor in the northern climates and a low SHGC in the south would be desirable.

The NFRC Ratings are used for the ENERGY STAR window, door and skylight energy efficiency guidelines set by the United States Environmental Protection Agency. The guidelines are geographic and climate specific.

Another very good source of information is the Efficient Windows Collaborative where general rating information can be found as well as specific methods to calculate energy savings.

The building code also includes specifics on fenestration testing and labeling. The performance data is then certified by a third party independent certification agency.  The certification agency issues certification documentation and authorizes the product’s manufacturer to label their product in accordance with the code requirements.  Certification programs, such as the WDMA Hallmark Certification Program exist to build consumer confidence through rigorous testing and inspections ensuring compliance with referenced air, water, structural and impact performance standards as well as the specified materials and components requirements. NFRC also operates a certification program for the energy performance ratings. This allows manufactured products to appropriately label their products to meet or exceed the applicable code requirements. The product certification program for fenestration products are based on the fact that this is a documented design that is third party tested and certified with ongoing third party plant inspections inclusive of quality systems to ensure the product continues to be manufactured to the same design that was tested.  A product’s certification system includes standardized procedures for testing, evaluation and ongoing third party plant inspection follow-up.  This allows for assurance that products continue to be made as they were tested. This is an improvement over systems using evaluation reports and adds another layer of third party plant surveillance.  The product certification bodies that operate program such as the WDMA Hallmark Certification Program, are accredited by the American National Standard Institute or ANSI.  ANSI is also an accrediting organization for certified programs and certification programs are under the oversight of the International Organization for Standardization to the ISO IEC 17065 Conformity Assessment for Body Certifying Products. ANSI is a signatory to the International Accreditation Forum and is part of the multilateral arrangements between countries on certification of body and laboratory approval requirements.

Look for products that are tested, rated and certified to the industry standards such as the North American Fenestration Standard and National Fenestration Ratings Council standards and take into consideration the specific application under the various geographic environmental conditions the building will be exposed to.

John McFee

VP of Certification Programs, WDMA

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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.

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Find window, door, and skylight manufacturers. 

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