Full Circle: Fenestration for the Complete Building Envelope

Windows, doors, and unit skylights comprise one performance standard highlighting integral components.

December 2005
Advertorial course provided by WDMA

Jeffrey F. Lowinski

Continuing Education

Use the following learning objectives to focus your study while reading this month’s Continuing Education article.

Learning Objectives - After reading this article, you will be able to:

  1. Identify products included in the Standard/Specification.
  2. Understand gateway performance requirements and product classes.
  3. Be aware of significant changes, revisions and new inclusions.
  4. Acknowledge basic terms and testing procedures.

Released and ready for specification, a new standard has hit the streets, and it�s sure to be noticed by the architectural design community and building code officials in the U.S. and Canada.

The completion of AAMA/WDMA/CSA 101/I.S.2/A440-05, Standard/Specification for Windows, Doors, and Unit Skylights marks a unique turning point for the industry. Developed by representatives from the Window & Door Manufacturers Association (WDMA), the American Architectural Manufacturers Association (AAMA), and the Canadian Standards Association (CSA), the standard is the first edition jointly published by all three organizations. More importantly, it is the first standard that gives manufacturers the tools to produce products under a single standard that can be distributed in the U.S. and cross-border to the neighboring building and construction communities of Canada.

The release of AAMA/WDMA/CSA 101/I.S.2/A440-05, completed earlier this year, is pivotal to WDMA�s ongoing success in offering and promoting performance-based standards, developed by a consensus of input from various representatives of the fenestration industry. WDMA worked laboriously with the other associations over the last decade to develop a standard/specification for windows, doors and unit skylights that harmoniously crosses association lines, as well as borders. AAMA/WDMA/CSA 101/I.S.2/A440-05 brings to the architectural and building codes community a compendium of specifications that reflect current, real-world performance standards.

Five different performance classes of windows, doors, and unit skylights are included in the standard/specification.
Photo courtesy of Marvin Windows and Doors

At the end of last year, WDMA released a major revision to their standards on interior architectural doors called the Industry Specification for Architectural Wood Flush Doors or I.S. 1A-04 (see Architectural Record magazine, November 2004, pages 269-273). This revised standard focuses on distinct performance levels and application-driven specifications. I.S.1A now joins with AAMA/WDMA/CSA 101/I.S.2/A440-05 to provide the industry and the end-user with complete and comprehensive standards that ultimately aid the construction community in specifying fenestration products thoroughly, precisely, and accurately.

Unit Skylights

Unit skylights are one of the many noteworthy inclusions in AAMA/WDMA/CSA 101/I.S.2/A440-05 Standard/Specification for Windows, Doors, and Unit Skylights. �It�s the first complete, performance-based fenestration standard that includes unit skylights,� said Roland Temple, Compliance and Certification Coordinator, VELUX America, Greenwood, S.C. Temple is a member of WDMA�s Exterior Fenestration Standards Committee and also served as the skylight representative to the U.S./Canadian Structural Harmonization Task Force. �This is the first complete guide for skylights. Previously, there was no single, unified standard on how unit skylights should perform,� he said. �There have been references in predecessor documents, but nothing as complete and encompassing as this. This standard/specification gives manufacturers one document to test to for all the performance requirements for skylights,� Temple added.

Unit skylights, said Temple, are defined as factory-assembled fenestration consisting of a single panel of glass or plastic installed in a sloped or horizontal orientation. Unit skylights are fixed (non-operable) or venting (operable). They are designed to allow for natural daylighting and ventilation in operable units.

The Standard/Specification gives manufacturers one document to test to for all the performance requirements for skylights.
Photo courtesy of VELUX America

Temple added that the specification covers a range of applications, from residential to commercial. �The standard identifies different performance criteria, which allows manufacturers to have products rated for various levels, depending on the application,� he said. �For the building code community, it�s something they�ve been looking for � a way to identify different characteristics of skylights and other products and how they should perform,� he added.

Side-hinged Exterior Doors

Prior to the release of AAMA/WDMA/CSA 101/I.S.2/A440-05, there was some confusion in the construction community about what specific performance criteria were necessary for side-hinged doors. When ANSI/AAMA/WDMA 101/I.S.2-97 and AAMA/WDMA 101/I.S.2/-NAFS-02 were put into the IBC and IRC, an exemption was created for exterior side-hinged doors and other products outside the scope of the standards, allowing them to be tested using ASTM E330 structural testing only. This exemption created some confusion for code officials, especially regarding exterior side-hinged doors containing glazing. Some jurisdictions insisted any swinging door containing glazing should meet 101/I.S.2-97 or 101/I.S.2/NAFS-02 standards, while others exempted some types of swinging patio doors from the requirement.

The recently completed AAMA/WDMA/CSA 101/I.S.2/A440-05 includes a specification section specifically for side-hinged exterior doors, and it is hoped its inclusion in the 2006 edition of the IBC and IRC will rectify any remaining problems. AAMA and WDMA jointly developed a Technical Position Statement regarding �Exterior Side-Hinged Door Systems� to address concerns regarding the applicability of 101/I.S.2-97 and 101/I.S.2/NAFS-02 to side-hinged exterior door systems that contain glazing. They agreed that these specifications were intended to apply to sliding glass doors containing certain typical elements including framed lower track systems. These types of framed sliding glass doors operate in a manner consistent with horizontal sliding window units, and as such, it was determined reasonable to expect that they would be able to perform in a similar manner during water penetration testing. (This Technical Position Statement is available at www.wdma.com).

The requirements in AAMA/WDMA/CSA 101/I.S.2/A440-05 governing side-hinged exterior door systems clear up some of the ongoing confusion about side-hinged doors and what types are addressed by the Standard/Specification. The standard/specification includes side-hinged exterior doors, sliding doors (often referred to as patio doors), dual-action side-hinged doors, and fixed doors (not interior doors). More importantly, the standard makes specific recommendations based on the type of door and where it is used. As in this standard and others developed recently by WDMA, performance and applicability to the built environment are critical components of the documents.

One of the most significant changes is the inclusion of requirements for side-hinged exterior doors. Side-hinged exterior door systems have requirements that are quite different from window, sliding door, and unit skylight products, both in design and application. As the primary means of entry to a building, exterior doors are required to not only protect against the elements, but are also required to allow for ease of access and emergency escape and rescue. Issues concerning accessibility by the disabled also need to be addressed in product design. In addition, consideration must be given to escape during emergencies such as fire, and in some cases, the door system is required to act as a barrier to fire. An exterior door system can be expected to be operated a significantly greater number of times and to a greater severity during its design life than a typical window or unit skylight assembly. As a result, cycling performance is evaluated, as well as other criteria specific to these types of fenestration products. Finally, it is not always feasible or necessary for side-hinged door systems to meet the substantial water penetration resistance requirements of other fenestration products in cases such as but not limited to, accessibility requirements and/or the application of products in weather-protected areas.

Enter the Next Generation

�This is a �next generation� standard, completely revised and updated,� said Joe Hayden, Senior Certification Engineer, Pella Corporation, Pella, Iowa. �It now includes all types of hinged doors, formerly known as patio and terrace doors and encompasses entry doors as well. In addition, this is an international standard, with the new version adopted by the Canadian Standards Association. It�s a single-source specification for windows, doors, and unit skylights for both the U.S. and Canada,� he said. Hayden chairs WDMA�s Exterior Fenestration Standards Committee.

Addressing Doors in the Real World

Overall, AAMA/WDMA/CSA 101/I.S.2/A440-05 contains provisions for side-hinged exterior doors that are more appropriate for their typical design and intended use. However, hinged doors, whether used as a required exit, as is the case with most entry doors, or as part of non-required exit systems as is often the case with �patio doors� or French doors (and other similar terms), do not typically include track systems that would permit the same level of water penetration resistance as sliding glass doors. In fact, entry doors used as required exits also have threshold limitations imposed to allow for ease of access and emergency escape and rescue. AAMA and WDMA memberships did not intend and do not expect hinged doors to meet the same level of water penetration as sliding glass doors. For this reason, and because a side-hinged exterior door can be expected to operate a significantly greater number of times, the introduction of a Cycling Performance category and a �Limited Water� (LW) rating was developed.

Each product type in the window, door and skylight specification has specific performance requirements.
Photo courtesy of Pella Corporation

Limited Water Penetration Resistance Testing and Performance

The �Limited Water� (LW) rating for exterior side-hinged doors is an important part of the document, again, focusing on real-world applications. The LW product type designation concludes that the water penetration resistance performance is achieved by testing at a pressure less than the minimum test pressure required for the indicated performance class and performance grade (design pressure). LW ratings are only permitted for side-hinged door systems and are not allowed for any other product type.

Performance Classes and Levels

Five performance classes of windows, doors, and unit skylights are included in the Standard/Specification. The performance classes are designated R, LC, C, HC, and AW. This classification system provides for several levels of performance. Flexibility in the standard and determining applicability, depending on the environment, is critical to the proper implementation of the standard. For example, the performance class rating should be regarded as an indication of the level of performance, with the least stringent requirements established for the R performance class and the most stringent for the AW performance class.

The following descriptions can be used as a general guide in helping to determine which class is likely suited for a particular application:

R: commonly used in one- and two-family dwellings.

LC: commonly used in low-rise multi-family dwellings, low-rise professional offices (doctor, dentist, law), libraries, and low-rise motels.

C: commonly used in lighter-use industrial buildings and factories, hotels, and retail sales buildings.

HC: commonly used in hospitals, schools, institutions, dormitories, government or public buildings, and other facilities where heavy use of the fenestration products is expected. Also, commonly used on mid-rise buildings with increased loading requirements.

AW: commonly used in hospitals, schools, institutions, and public buildings, or on high-rise, and mid-rise buildings to meet increased loading requirements; also used in buildings where possible misuse of the fenestration products is expected.

Other design criteria include minimum design pressures, uniform load structural test pressures, and water penetration resistance test pressures for the fire performance classes. (Table 1)

The architect and specifier can select the appropriate level of performance depending on map wind speed, climate conditions, height of installation, type of building, type of window, door or unit skylight, durability, and other factors. In many cases, the appropriate level of performance classification will not correspond with the general use of the building or the use group occupancy assigned to the building in accordance with the local building code. For example, many residential buildings are constructed in locations subject to severe weather that require high-performance fenestration products rather than those that meet only the R requirements. On the other hand, many hospitals, schools, and institutions may successfully use products meeting R, LC, and C requirements. In other words, it�s up to the architect and specifier to fine-tune their selection for the application, and this standard/specification will help them do just that.

Performance Grade Designations

Performance grades in AAMA/WDMA/CSA 101/I.S.2/A440-05 are based on design pressure, which is designated by a number following the type and class designation. For example, a double-hung R-class window designed H-R15 or H-RM720 establishes the design pressure of 15 pounds per square foot (psf) or approximately 720 pascals (Pa). If the rating is desired in SI (metric) units, the design pressure in pascals (Pa) is preceded by an �M.� In its most basic sense, design pressure is the wind load pressure a product is rated to withstand. Products included in the standard/specification are designated by the performance grade or design pressure for which they have been successfully tested and noted in pascals or psf. The uniform load structural test pressure for windows and doors is 150 percent of the performance grade (design pressure) and 200 percent for unit skylights and roof windows. The water penetration test pressure is 15 percent of the performance grade (design pressure) for R, LC, C, and HC products and 20 percent of the performance grade (design pressure) for AW products but never less than 140 Pa (2.9 psf) except limited water on side-hinged door systems only. In addition, products shall be permitted to be tested to optional performance grades (design pressures) higher than the minimum performance grades (design pressures) specified. (Table 1)

Table 1
Gateway Requirements
Each product has a defined gateway set of primary requirements.

Gateway Requirements

Each product type has a defined �gateway� set of primary requirements for the applicable product type before the manufacturer�s tested product is allowed into the performance class. Gateway performance requirements are the minimum allowable performance levels that a gateway test specimen achieves in order to be rated with a particular classification of R, LC, C, HC or AW. The gateway test specimen size must be equal to or larger than the specified designation parameters in both height and width. Generally, the minimum allowable performance levels and the gateway size change as the classification changes. All gateway test specimens shall achieve certain minimum performance levels for air leakage resistance, water penetration resistance, uniform load, and where required, forced-entry resistance and operating force. All gateway test specimens shall achieve certain additional minimum performance levels of auxiliary (durability) and material tests specific to the product operator type.

Specialty type products are also included in the standard/specification. Examples of specialty products are non-standard geometric shapes such as, but not limited to, circle tops, ellipsoids, and other non-rectangular shapes. Specialty products shall comply with all applicable material, component, and hardware requirements of this Standard/Specification. However, specialty products shall not be required to comply with any minimum gateway width and/or height requirements of this Standard/Specification. (See page 114 of standard.)

Maximum Size Tested

The maximum size tested, or MS, is required on designations reporting or recording individual product performance. The MST shall be designed by width times (x) height in millimeters, e.g., 705 x 1503. The MST shall be permitted to be additionally shown in inches, e.g., 705 x 1503 (28 x 59).

Test size is a critical factor in determining compliance with the standard/specification. Each product has a defined gateway set of requirements. One of the gateway requirements is minimum gateway test size. Products are to be tested at the minimum gateway test size or a larger specimen size as a condition of entering the performance class. After passing all of the performance requirements for the product type, performance class, and performance grade, the product shall be designated with the appropriate primary designator. (Figure 2)

Figure 2
Primary designator
Both primary and secondary designators indicate the type of product, size, and other testing parameters.

This designation shall only be applied to production sizes of identical construction equal to or smaller than the size tested in both width and height. There are some glazing exceptions noted in the standard/specification. For downsized door products where structural material within the leaf has been removed to accommodate a lite insert equal to that of a larger leaf, an additional positive and negative uniform load structural test will be conducted on the downsized specimen to verify the structural performance.

Users shall not be confused by the terms �minimum test size� and �maximum size tested.� In order to claim that a product is entitled to be included in a given performance class, it needs to meet or exceed all of the minimum requirements for the performance class. This set of minimum requirements is the gateway requirements for the performance classes. After achieving the performance class, the manufacturer is permitted to test a second time at a reduced specimen size. The first test at the �minimum gateway size or larger� provides apples-to-apples comparisons of products rated in the same performance class. Since the second test is not required to be at the minimum test size, it becomes necessary to report to the user the actual specimen size during the second test. Indicating the �maximum size tested� fulfills this reporting function. For this reason, the MST is a mandatory part of the product rating, but should never be included in a project specification.

Those who wish to prove compliance with both the gateway and the optional performance requirements (Table 3) on the same test specimen will test a specimen equal to or greater than the minimum gateway test size for that product type.

Any geometric shape that fits within the rectangular gateway size (or larger test size) for a particular product type is permitted to be qualified by the rectangular shape, provided that the frame, sash, leaves, panels, hardware, hardware location, components, and construction remain the same.

Table 2
Product Types
Product designations indicate the type of window, door or unit skylight.

Other Standard/Specification Significant Changes

In addition to the specific changes noted, the following revisions have been included in the new standard/specification:

  • The expansion of the product rating system to provide a primary designator similar to that in current use and a new secondary designator that allows reporting of performance criteria such as negative design pressures, water penetration resistance test pressures, and optional performance tests;
  • Revision of gateway requirements to an SI (metric) basis, while still maintaining the inch-pound (psf) nominal rating intervals common to previous standards/specifications;
  • The increase in the number of product operator types from 26 to 30 (Table 2);
  • The addition of Canadian air infiltration/exfiltration levels and operating force requirements;
  • The revision to U.S. operating force requirements to initiate motion to �Report Only�;
  • Updated glass strength standard, as the basis for glass selection, to ASTM E 1300-02;
  • Introduction of cycle/operation testing for side-hinged doors;
  • Introduction of hardware water testing, vertical load, and forced entry resistance testing for doors;
  • Addition of numerous new sash, frame, and glazing material requirements;
  • Elimination of the words residential, light commercial, heavy commercial, and architectural from the performance class definition and their replacement by the simple designations R, LC, C, HC, and AW;
  • The addition of six new requirements for plastic glazing;
  • Skylight structural test load changed from 1.5 times design pressure positive, 2.0 times design pressure negative to 2.0 times design pressure both positive and negative;
  • Specimen structural damage limiting retests due to glass breakage or hardware failure to two; and
  • Finished framing and cladding materials not allowed to contain more than 0.02 percent lead by weight.

The Window & Door Manufacturers Association (WDMA) is a trade association representing the leading U.S. and Canadian manufacturers and suppliers of windows, doors and skylights for the domestic and export markets (www.wdma.com). For further information, contact WDMA at: 1400 E. Touhy Ave., Suite 470, Des Plaines, IL 60018; phone 847-299-5200; e-mail:admin@wdma.com.

The standard/specification progression

The history and evolution of the AAMA/WDMA/CSA 101/I.S.2/A440-05 standard/specification runs deep, and the basis for the new release references a list of predecessor documents, including: AAMA 101-93 Voluntary Specifications for Aluminum and Poly (Vinyl Chloride) (PVC) Prime Windows and Glass Doors; NWWDA I.S.2-93, Industry Standard for Wood Window Units; AAMA/NWWDA 101/I.S.2-97, Voluntary Specification for Aluminum, Vinyl (PVC) and Wood and Glass Doors; AAMA/WDMA 101, I.S.2/NAFS-02, Voluntary Performance Specification for Windows, Unit Skylights, and Glass Doors; AAMA/WDMA 1600/I.S. 7, Voluntary Specification for Skylights; and CAN/CSA A440-00/CSA A440.1-00, Windows/User Selection Guide to CSA Standard CAN/CSA A440-00, Windows.

Figure 1
Short-form Specification
Product designations indicate the type of window, door or unit skylight.

Finally, and perhaps even more importantly, the standard will be included in the International Code Council�s 2006 I Codes, International Building Code (IBC) and International Residential Code (IRC), and has been submitted to the Standards Council of Canada for inclusion in the National Building Code of Canada, said Jeffrey D. Lowinski, Acting President, WDMA.

�The IBC and the IRC will reference AAMA/WDMA/CSA 101/I.S.2/A440-05. The new document is the first truly harmonized North American fenestration standard,� he said.

�The standard has been reformatted and includes a tremendous amount of detail, in an easy to use and reference document,� Lowinski continued. �In addition to the performance grades and other design criteria, it is a succinct and detailed standard which includes extensive references and other in-depth information for designers and specifiers.�

Specific test methods, material requirements, components, tables, examples and referenced documents round out the standard/specification and provide the in-depth information that architects and specifiers need to make proper design decisions for the selection of fenestration products. Referenced publications, a complete definition of related terms as well as details and other specific construction drawings are part of the standard/specification (AAMA/WDMA/CSA 101.I.S.2/A440-05 is available for purchase from WDMA offices or on-line at www.wdma.com).

�It establishes easy-to-use performance classes and tells the specifier exactly what the code criteria is and what it means. The standard will help the architect match his window, door or unit skylight to the specification and application,� Lowinski added.

The standard/specification incorporates the basic content of AAMA/WDMA/101/I.S.2/NAFS-02 relating to windows, patio doors, and unit skylights. It also incorporates new requirements for products not covered by AAMA/WDMA 101/I.S.2/NAFS-02, including requirements by the Joint Exterior Door Task Group for side-hinged exterior doors. There have also been numerous revisions to requirements carried over from some of the aforementioned standards/specifications to improve the clarity and uniformity overall of the rating system. To simplify the writing of performance specifications for windows, doors, and unit skylights, the authors prepared a �short-form specification� (Figure 1) which is recommended for use whenever possible. It may be used for most common types and classes of windows, doors, and unit skylights by merely inserting the applicable standard/specification designation(s).


AAMA/WDMA/CSA 101/I.S.2/A440-05, standard/specification for Windows, Doors, and Unit Skylights applies to both operating and fixed, prime and replacement windows, doors and unit skylights installed into exterior building envelopes. It establishes material-neutral, minimum and optional performance requirements for windows, doors, and unit skylights. AAMA/WDMA/CSA 101/I.S.2/A440-05 concerns itself with the determination of design pressure and related performance ratings. Performance requirements are used whenever possible and prescriptive requirements used only when necessary. When products are tested to the gateway requirements, or to the gateway and optional requirements, a rating shall be determined and a test report shall be permitted to be issued. It applies to testing and rating products. The tested rating applies to products of identical construction, with width and height less than or equal to the tested size.

Certification procedures are not part of the standard/specification. Any manufacturer that can demonstrate conformance to this standard/specification is eligible to participate in WDMA�s Hallmark Certification Program. The WDMA Hallmark Certification Program gives builders, architects, specifiers, and consumers an easily-recognizable means of identifying windows, doors, and skylights that have been manufactured in accordance with the appropriate WDMA and other referenced performance standards.

This standard/specification was jointly prepared by the CSA Technical Committee on Windows, Doors and Skylights, under the jurisdiction of the Strategic Steering Committee on Building Products and Systems; the U.S./Canadian Structural Harmonization Task Force; and the Joint Exterior Door Task Group. It has been formally approved by the members of AAMA, by the CSA Technical Committee, and by the members of WDMA.

The release of AAMA/WDMA/CSA 101/I.S.2/A440-05 brings to the architectural and specification community a complete, detailed, and up-to-date reference, acknowledged and referenced by building code bodies, that allows users to select the most appropriate product for the application, whether it�s residential, commercial, institutional or other building type.

Highlights of AAMA/WDMA/CSA 101/I.S.2/A440-05
  • Single standard for both U.S. and Canadian markets for windows, doors, and unit skylights.
  • First complete performance-based fenestration standard that includes windows, doors, and unit skylights.
  • Includes side-hinged exterior doors, sliding doors (often referred to as patio doors), dual-action side-hinged doors, fixed doors (not interior doors), and establishes a Limited Water or LW rating to test products.
  • Included in the International Code Council�s 2006 I Codes, with the temporary exception of swinging entry door systems, and has been presented to the Standards Council of Canada for inclusion in the National Building Code of Canada.

AAMA/WDMA/CSA 101/I.S.2/A440-05 contains a detailed, multi-page glossary of terms pertinent to the document. Selected definitions include:

Certification�a process that indicates a representative sample of a product line has been tested, that the product meets specified requirements, and that the product is subject to ongoing inspections by an outside certification agency.

Design pressure (DP)�the wind load pressure a product is rated to withstand.

Design wind load�the wind load pressure a product is required by the specifier to withstand in its end use application.

Fenestration�openings in the building envelope, such as windows, doors, and unit skylights, designed to permit the passage of air, light or people.

Gateway performance requirements�the requirements for minimum gateway test size, air leakage resistance, structural design load, and overload testing, water penetration testing, forced-entry resistance, and auxiliary testing which are the conditions permitting a product entry into a performance class. They are specifically indicated for each product operator type.

Gateway test size�the test specimen size specified to enter a performance class.

Leaf�a part of a side-hinged door system, glazed or unglazed, surrounded by a frame. Leaves can be fixed in place (inoperable) or movable (operable).

Limited water (LW) (as a designation)�indicates that the water penetration resistance performance is achieved by testing at a pressure less than the minimum test pressure required for the indicated performance class and performance grade (design pressure).

Minimum gateway test size�the test specimen size specified to enter a performance class at the lowest or minimum level.

Negative pressure�pressure acting in the outward direction.

Operating force�the force required to maintain a sash, leaf or panel in motion in either the opening or closing direction.

Performance class�one of the five performance classes (R, LC, C, HC, and AW). This classification system provides for several levels of performance so the purchaser or specifier is permitted to select the appropriate level of performance depending on the climatic conditions, height of installation, type of building, etc.

Performance grade�the minimum level of design pressure (air, water, wind) to which a representative test specimen is tested to achieve a particular rating.

Positive pressure�pressure acting in the inward direction.

Pressure�differential force per unit area between the interior and exterior surfaces of the test specimen.

Side-hinged door system�a door having, at a minimum, a hinge attachment of any type between a leaf and jamb or edge of another leaf but having a single, fixed vertical axis about which the leaf rotates between open and closed positions. These systems include, as a minimum, a single operating leaf, surrounding frame, and components. The surrounding frame has vertical and horizontal members that are joined at the intersections and fully encompass the operating and/or fixed leaf/leaves. Additional operating and/or fixed leaves, side lites, transoms, framing and mullions are often included.

Specification�a written document often accompanying architectural drawings, giving such details as scope of work, materials to be used, installation method, required performance, and quality of workmanship for work under contract.

Structural test pressure (STP)�the pressure differential applied to a window, door system or unit skylight. In this standard/specification, the STP is 150 percent of design pressure for windows and doors and 200 percent of design pressure for unit skylights.

Test specimen�a complete, fully functioning window, door or unit skylight supplied by the applicant, and fitted in the test apparatus in accordance with the manufacturer�s installation instructions (including manufacturer�s instructions for clearance and shimming).

Water penetration�penetration of water beyond the vertical plane intersecting the innermost projection of the test specimen, not including interior trim and hardware, under the specified conditions of air pressure difference across the specimen.

Wind load resistance�the ability of a window, door or unit skylight to resist the structural effects of differential pressure induced by wind, usually determined relative to a design pressure derived from the building codes.

Don�t Be Misled

Fenestration products not intended to be tested to the standard/specification include:

  • Interior windows and doors
  • Vehicular-access or garage doors
  • Sloped glazing other than unit skylights or roof windows
  • Curtain wall and storefront windows
  • Storm windows and doors (except when incorporated in dual windows and dual doors)
  • Commercial entrance systems
  • Sunrooms
  • Revolving doors
  • Site-built door systems
  • Commercial steel doors


Originally published in the December 2005 issue of Architectural Record.