{"id":205807,"date":"2023-08-18T16:00:38","date_gmt":"2023-08-18T20:00:38","guid":{"rendered":"https:\/\/www.constructionspecifier.com\/?p=205807"},"modified":"2023-08-11T10:24:56","modified_gmt":"2023-08-11T14:24:56","slug":"key-considerations-for-designing-fenestration-system-for-success","status":"publish","type":"post","link":"https:\/\/www.constructionspecifier.com\/key-considerations-for-designing-fenestration-system-for-success\/","title":{"rendered":"Key considerations for designing fenestration systems for success"},"content":{"rendered":"
\"Photos<\/a>
Photos courtesy Simpson Gumpertz & Heger Inc.<\/em><\/span><\/figcaption><\/figure>\n

By Bradford J. Antes, PE, and Erin E. Regan, PE<\/strong><\/p>\n

The design phase of a building project allows the design team to select fenestration systems that meet the needs of a project and set up the building for success during and after construction. Design teams must balance performance and practicality to achieve a successful installation while maintaining required fenestration performance.<\/p>\n

This article will discuss some key items to include in the project documents during the design of a new building to help achieve a successful fenestration installation come construction.<\/p>\n

Specifications<\/strong><\/p>\n

The first description of a new fenestration system will be in the project specifications, where there is a dedicated section describing the system, performance, and testing requirements, as well as other desired characteristics of the specific system.<\/p>\n

Performance requirements<\/strong><\/p>\n

There is a wide range of fenestration materials available for both commercial and residential buildings, including aluminum, steel, wood, and fiberglass. The American Architectural Manufacturer\u2019s Association (AAMA) instituted performance multiple grade standards for fenestration products in accordance with national and international building codes and other similar regulations.<\/p>\n

Residential (R), light commercial (LC), commercial window (CW), and architectural window (AW) grades are available depending on the application, design pressure, water penetration resistance, air leakage resistance, and deflection under design loading among others. In commercial buildings,
\nLC, CW, and AW grades can be used depending on project performance requirements. For example, LC windows are not tested for maximum allowable deflection of unsupported spans, making them unsuitable for projects with high design loads or specific deflection criteria. It is important to note R-grade windows are intended for smaller\/shorter residential buildings and single-family residences and are not appropriate for larger and taller multifamily buildings (which are classified as commercial buildings in most codes).<\/p>\n

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Laboratory testing reports should be included in the specifications as a required submittal and accompany the specified window product data. Typical testing reports have expiration, as well as retention dates that can be missed if the project team is not paying close attention. Often, contractors will submit documents for the project, including test reports that can range from four to 20 years old. Unless the manufacturer can provide written confirmation that the window\u2019s design has not changed since the date of the test report, indicating the report is still valid to describe the performance of the windows, a recent test report (within four years) should always be provided. This ensures the system meets current test standards and procedures.<\/p>\n

Often, designers will propose a window manufactured domestically based on aesthetics, track record, or familiarity with a certain brand. However, the contractor will sometimes propose a foreign alternate during the bid phase, often due to cost. Foreign-manufactured windows are typically tested to different standards that may not be equivalent to U.S. testing requirements.<\/p>\n

For example, windows passing European (EN) test standards such as DIN EN 12208, Windows and Doors <\/em>– Watertightness \u2013 Classification<\/em>, and DIN EN 12207, Windows and Doors – Air Permeability \u2013 Classification<\/em>, do not equate to passing American test standards such as ASTM E331, Standard Test Method for Water Penetration of Exterior Windows, Skylights, Doors, and Curtain Walls by Uniform Static Air Pressure Difference<\/em>, or ASTM E283, Standard Test Method for Determining Rate of Air Leakage Through Exterior Windows, Skylights, Curtain Walls, and Doors under Specified Pressure Differences Across the Specimen<\/em>.
\nIf this substitution is approved, the owner will buy windows that are not the same performance as what they bought in the original design; although it is worth noting performance may end up being better in some cases.<\/p>\n

\"Figure<\/a>
Figure 1<\/b> The National Fenestration Rating Council (NFRC) sticker. <\/span><\/figcaption><\/figure>\n

The National Fenestration Rating Council (NFRC) product certification is necessary for windows to be installed in the U.S, as stated in the International Energy Conservation Code<\/em> (IECC<\/em>). The U-factor is a key element for new fenestration products and is listed on the product-specific NFRC label. NFRC labels list energy performance ratings for the entire fenestration product, which also can include the solar heat gain coefficient, visible light transmittance, and air leakage (Figure 1).<\/p>\n

Code language always refers to the fenestration product U-factor, but often a center-of-glass (COG) U-factor is sometimes the only measurement submitted for a product. It is important for designers to be aware of this and the associated differences, as a COG U-factor will show much better performance than the U-factor for the entire window product, which includes window framing and other internal components. Designers should specify both values or, at minimum, the U-factor required for the entire fenestration product. As described, products tested to foreign standards for thermal performance may not be equivalent to their American counterparts and may require supplementary testing. If additional testing is required for a substitution, architects and designers can request for the product to be tested by an approved third-party laboratory. The testing should be paid for by the manufacturer or the contractor who proposed the change.<\/p>\n

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Safety glass<\/strong><\/p>\n

With some exceptions, safety glazing is required in windows as per the International Building Code<\/em> (IBC<\/em>) when all the following glazing conditions are met:<\/p>\n