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July - August 2003

AAMA ANALYSIS
 

NAFS-2 
New Exterior Side-Hinged Door Spec Address Real-World Performance
by Tracy Rogers

The latest effort to harmonize U.S. and Canadian performance standards for windows, glass doors and skylights (101/I.S.2/A440 - a.k.a. North American Fenestration Standard, or “NAFS-2”), includes a new specification for exterior side-hinged doors developed by the Joint Exterior Door Task Group.

A major step forward, this imbedded specification is the first all-encompassing standard for rating such products. While providing for the usual aspects of air leakage and structural performance requirements, it recognizes that exterior side-hinged doors are quite different from windows and sliding glass doors in three key aspects: accessibility requirements, operating frequency and water penetration.

To review how the Exterior Side-Hinged Door specification addresses such issues, the 101/I.S.2/A440 draft standard must be considered.

Relating Door Performance to Standard Performance Grades

Products included in 101/I.S.2/A440, such as ANSI/AAMA/NWWDA 101/I.S. 2-97 before it, are designated by the Performance Grade (Design Pressure) for which they have been tested successfully. Minimum design pressure ratings define the performance classes as indicated in the following table.
Windows, Doors and Unit Skylights

Windows, Doors and Unit Skylights

Performance Class
(Design Pressure
  Minimum Performance
Pa (psf)
  Design Pressure
R = 15 = 750 Pa (15 psf)
LC = 25 = 1250 Pa (25 psf)
C = 30 = 1500 Pa (30 psf)
HC = 40 = 2500 Pa (40 psf)
AW = 40 = 2000 Pa (40 psf)
Commonly used in:
R – One and two family dwellings. 
LC – Low-rise multifamily dwellings, low-rise professional offices (doctor, dentist, lawyer), libraries and low-rise motels.
C – Lighter use industrial buildings and factories, hotels, and retail sales buildings.
HC – Hospitals, schools, institutions, dormitories, government or public buildings and other buildings where heavy use of the fenestration product is expected. Also commonly used on mid-rise buildings with increased loading requirements.
AW – Hospitals, schools, institutions, and public buildings, or on high-rise and mid-rise buildings to meet increased loading requirements. Also commonly used in buildings where possible misuse of the fenestration products is expected.

Operating Cycle Testing
While a window may be operated once or twice a week, and a patio door operated sporadically and typically seasonally, an exterior side-hinged door may be opened and closed (often severely) several times a day, year-round. For this reason, the standard requires side-hinged doors to be cycle-tested and evaluated for possible premature component wear. 

Performance classes defined under 101/I.S.2/A440 are used to define the number of cycles required for successful operational testing.

H2O Penetration Performance
Perhaps the most significant aspect of the new exterior side-hinged door standard is its real-world treatment of water leakage performance.

Exterior side-hinged doors are limited by design and accessibility requirements that specifically affect water penetration performance. For instance, restrictions under the Americans with Disabilities Act (ADA) include limiting threshold-sill height to no more than ½-inch (12 mm). This design limitation makes it extremely difficult for an exterior side-hinged door system to pass the traditional water penetration tests (i.e., no leakage when subjected to water spray and the 15/20-percent pressure differential concurrently and still meet accessibility prerequisites). 

Because such doors typically are installed in weather-protected areas, experience shows there are few, if any, instances of significant leakage problems. Thus, it is not always feasible or necessary for them to meet the substantial water penetration resistance requirements of other fenestration products. 

For the first time, the standard introduces an allowable exception for side-hinged door systems. It would test and rate them for water penetration resistance at an air pressure differential that ranges from zero up to any selected pressure less than the 15/20 percent of design pressure indicated by the performance class. This better simulates real-world conditions where rain impacts the door but is not driven inside under a significant pressure differential. The exception does not apply to any other product type. 

Products tested and rated under this “limited water” exception are identified by a product designation code of “LW.” For example, a limited-water rated side-hinged door would have the product designation of LW-SHD.

The Exterior Side-Hinged Door Specification requires the door to be tested for water leakage with hinges and representative locking/latching hardware installed and fully operable in normal configuration (please note that this does not mean noted, taped or sealed off or specially caulked). All hardware must conform to the applicable requirements of six referenced Building Hardware Manufacturers Association (BHMA) standards. 

In cases where the locking/latching hardware is not supplied by the door manufacturer in order to meet the standard, the hardware used in the installed door must demonstrate water penetration resistance and structural equivalence to that with which the door was originally tested (AAMA 930).

Looking for Approval
The new 101/I.S.2/A440, (“NAFS-2”) standard, with its exterior side-hinged door requirements, is now under review and balloting for association approval. The ANSI canvas is to be completed in 2005. 

Tracy Rogers of Intertek Testing is the first vice-president of the American Architectural Manufacturers Association Door Council.

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