Window/Wall Interface
Looking at Walls as an Integrated System
by John Lewis

Water penetration of walls, especially around doors and windows, has become a major focus of attention in a number of venues. This ranges from hurricane damage prevention and associated code development, to litigation over alleged health effects due to moisture-induced growth of mold and mildew.

Doors and windows are obviously susceptible to water penetration where such problems occur. In most cases, however, water penetration is not likely to be due to deficient product design. AAMA-certified fenestration products which meet the code-mandated door and window standard AAMA/WDMA/CSA 101/I.S. 2/A440-05 or its predecessors must pass water leakage tests.

However, product certification does not ensure the intended performance of the fenestration product after installation. Even the best-designed product can allow water to penetrate if installed improperly. And, as with all products, performance levels decrease over time due to normal wear and tear.

Minimizing Water Penetration
The solution for minimizing the potential for water penetration at door and window openings is to take a step back and look at the wall in which the window is mounted as an entire system. The components of this system must interact properly to ensure the integrity of the “drainage plane” of the exterior wall. This concept focuses attention on the interfaces between wall components, not just on the components themselves.

The drainage plane consists of an appropriate weather-resistant barrier (WRB) – e.g., house wrap, etc.–that provides a unified path for rainwater that penetrates the exterior cladding to move down from roof to ground and away from the building.

From our industry’s perspective, the essential principle is that door and window units must integrate with the exterior facing material, sheathing and the WRB to form an effective drainage plane. Flashing and sealants are at the front line of this interface, and are great examples of how all elements in the wall system (as well as all participants in the supply and installation chain) must work together. This is necessary to realize the intended air infiltration and water penetration resistance of the installed fenestration products. It would be naïve to think that each player can continue handling its part and merely hoping that the resulting collection of products works together properly.

Wall Interface Council is Formed
In view of this, AAMA has formed a new Wall Interface Council (WIC) to represent the specific interests of manufacturers of such products. The WIC addresses standards and practices for integrating windows into various wall types and exterior facades. Now under the WIC’s umbrella, various committees and task groups are dealing with performance testing and national and regional requirements for flashing, sealants, glazing tapes, adhesives and related products. 

Ongoing activities include recently released updates of AAMA 711, Voluntary Specification for Self-Adhering Flashing Used for Installation of Exterior Wall Fenestration Products, and AAMA 800, Voluntary Specifications and Test Methods for Sealants, focusing on improved test methods. No fewer than seven additional standards or technical advisories are in various stages of development, covering enhanced and more definitive testing against consensus performance criteria, the selection and specification and/or the application of wall interface materials used in fenestration product installations. 

The fenestration industry might be looking at doors and windows as isolated components rather than thinking of the building envelope as a total system within which these products must be integrated. The AAMA Wall Interface Council is weighing in on the side of the systems view. All stakeholders are encouraged to participate. 

John Lewis serves as technical director for the American Architectural Manufacturers Association in Schaumburg, Ill. He may be reached at jlewis@aamanet.org. Mr. Lewis’ opinions are solely his own and do not necessarily reflect those of this magazine.

DWM
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