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Volume 7   Issue 6               June 2006

AAMA Analysis

A Practical Approach to Water Protection
by Dean Lewis

While it could be argued that some coastal code jurisdictions hit the snooze button after Hurricane Andrew’s 1992 alarm, other jurisdictions have upgraded their code requirements and noted significant success through the 2004 and 2005 hurricane seasons. 

Defining Acceptable Water Levels
Now, an ancillary problem has begun to gain notoriety: water penetration from wind-driven rain. Though engineering a product to eliminate water penetration under the most severe conditions is possible, the aesthetics, functionality and cost of such a product make this an impractical solution. Therefore, quantifying what degree of water entrance may be acceptable will be a key consideration in the development of a new standard. Perhaps it is a good sign when we begin to shift concern from how to keep buildings from being destroyed to how to keep their interiors high and dry in the face of the most powerful storms.

In response to the needs of the marketplace, AAMA has taken the lead in investigating the total issue of water control performance of windows under hurricane wind and rain conditions. Last fall, the AAMA Southeast Region formed a hurricane water penetration standard development task group to accomplish this mission. They started by gathering data on test methods that address real-world, indoor-outdoor pressure differentials due to hurricane winds, cycling to simulate actual time-pressure profiles (wind gusting) and effects of dynamic pressure (turbulent wind flow).

In the United States, fenestration products are tested commonly for water penetration in accordance with ASTM E 331 and ASTM E 547. These test methods subject the exterior surfaces of the fenestration product to a water application rate of 5 gal/ft2/hr–roughly equivalent to 8 inches of rain per hour–under a static pressure differential ranging from 2.9 psf (~34 mph) to 12.00 psf (~70 mph). These provide a repeatable representation of the hydrostatic pressure effects created by wind-driven rain events, but do not provide a realistic representation of the wind gusts and pulsating effects. The AAMA 501.1 dynamic test method utilizes a wind generator to create a more realistic wind-driven rain test. Other test methods, such as the Japanese Industrial Standard JIS A 1517 and the Australian/New Zealand AS/NZS 4284:1995, attempt to simulate the gusting effects of wind-driven rain by rapid pulsation of the static pressure. The similar ASTM E 2268 Standard Test Method for Water Penetration of Exterior Windows, Skylights, and Doors by Rapid Pulsed Air Pressure Difference was also examined. The task group then compared these existing test methods by subjecting the same test samples to the various tests.

A New Procedure
Upon review of the initial data, the task group began drafting a new AAMA voluntary procedure, provisionally entitled Voluntary Specification for Rating the Water Penetration Resistance of Windows and Doors Subjected to Severe or Extreme Wind-Driven Rain Conditions. At this point of the specification’s development, at the maximum test level, the preliminary target maximum permissible quantity of water that actually passes the inner plane of the product can be no more than two ounces after 300 pulsating wind cycles. That translates to two ounces of water about every ten minutes during a 100 mph hurricane. In, say, four hours of maximum storm wind exposure, that’s about 48 ounces–an amount that can reasonably be addressed. The quantity of acceptable uncontrolled water is reduced for the less severe test levels.

The practicality of designing a product that can eliminate water penetration requires some important considerations. Will it be aesthetically appealing? Will the operator type or emergency access be restricted? What maintenance will be required? How much will it cost? To balance the realistic necessity of addressing these considerations, AAMA is approaching development of this new standard with deliberate attention to maintaining aesthetic and financial satisfaction while minimizing uncontrolled water penetration. It is a stout challenge to be sure, but one that the AAMA membership is addressing head-on based on decades of technical expertise and experience in facing similarly complex engineering needs. 

Dean Lewis serves as certification manager for the American Architectural Manufacturers Association in Schaumburg, Ill. 

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