Volume 25, Issue 6 - November/December 2011

Metal Matters

Armed and Ready
Industry Resources Address Hurricane Mitigation
by Rich Walker

The 2011 hurricane season spanned June to November, Arlene to Rina. Between hurricanes, the United States was hammered with tropical storms and tornadoes. To mitigate damage to occupants and structures, the American Architectural Manufacturers Association (AAMA) offers voluntary specifications to help fenestration products, including architectural metal framed products such as windows, curtainwall and skylights, address severe wind-driven rain and the impact of wind-borne debris.

Product Performance
Doors, windows and unit skylights are typically selected based on local or state building code requirements. The primary consideration is structural integrity, to keep the unit intact and prevent the pressure of high-velocity wind from entering the building and causing catastrophic structural failure or life safety concerns. In tropical storms and hurricane wind-driven rain conditions, the product selected to meet the code requirements may experience water penetration when these extraordinary conditions exceed the performance rating for water penetration resistance.

AAMA 506-08 “Voluntary Specifications for Impact and Cycle Testing of Fenestration Products,” is cited in the 2010 Florida Building Code and in the 2012 International Residential Code. AAMA 506 was updated and published in July 2011 and uses existing ASTM test methods to qualify doors, windows and skylights as impact resistant. It includes all framing materials, including aluminum and other metals, covered by the standards and specifications listed in this document.

In addition to AAMA 506-11, AAMA 520-09 “Voluntary Specification for Rating the Severe Wind-Driven Rain Resistance of Windows, Doors and Unit Skylights,” rates a product’s ability to resist water penetration during the most severe weather events. This voluntary specification is based on a rapidly pulsed pressure differential method, recognizing that conditions encountered during tropical storms, hurricanes or severe thunderstorms are not static. The rating obtained from performing the testing cited in this specification is intended to exceed the water penetration resistance levels derived from other testing specifications (e.g., AAMA/WDMA/CSA 101/I.S.2/A440) currently in use.

Leaky Concerns
In the aftermath of tropical storms and hurricanes, questions were raised by some residents who experienced wind-driven rain leaking through or around their doors and windows that otherwise remained unbroken and structurally intact during these extraordinary events. Rain driven by high winds may enter the wall cavity of a home or building at any number of points, some well above the location at which they appear, such as the attic or roof, soffit or wall penetrations, such as exhaust fans. Running down the inside of the wall, it may exit the wall around the rough opening at a door or window.

Even though the window was properly anchored for structural integrity, it may leak if not correctly flashed and sealed. Doors and windows that are not installed plumb, square and in plane will not close properly. This leaves gaps, which, though very small, are sufficient to admit rain when driven by storm-force winds. The age of the door or window, condition of seals and weatherstripping, and other maintenance matters such as clogged drainage/weep holes, can contribute to leaks appearing during wind-driven rain conditions. All doors and windows should be regularly inspected for damage or wear, and repaired as needed.

“It also is important to review product limitations with property owners and to remind occupants of necessary precautions in the event of wind-driven rain and hurricane conditions, as some amount of water penetration during an extreme weather situation is possible.”

Architectural Matters
Architects may find themselves more frequently addressing these concerns and code requirements for those living and working in areas prone to severe windstorm events. In addition to specifying proper performance and installation of fenestration products, it also is important to review product limitations with property owners and to remind occupants of necessary precautions in the event of wind-driven rain and hurricane conditions, as some amount of water penetration during an extreme weather situation is possible.

Following wind-driven rain events, some may mistakenly think that water penetration is a defect of the product. In most cases, this is not true. Doors, windows and skylights tested to meet AAMA 520-09 are provided with ten performance levels. During the testing, pulsating pressure is applied for 300 cycles with water spraying in accordance with the specified performance level. Water penetration to the interior is monitored throughout the test. At the test’s conclusion, any water that penetrates the innermost plane of the product, passes through the product mainframe, or overflows the sill is collected and weighed. Products that pass the test and meet AAMA 520-09 are allowed no more than 15 ml, or approximately 0.5 ounces (per meter [39 3/8 inches] of sill width), of water into the interior under these extreme conditions.

Architects can use AAMA’s online Certified Products Directory to identify hurricane impact-resistant doors, windows and skylights. The site also features an online Publication Store where hurricane-related documents can be purchased, and an online directory of AAMA-accredited labs to perform necessary tests.

Rich Walker is the president and chief executive officer of the American Architectural Manufacturers Association in Schaumburg, Ill.

Architects' Guide to Glass & Metal
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