New Guides Make Window Installation in Foam-Sheathed Walls Easy

Originally published by: Applied Building Technology GroupOctober 17, 2016

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Window installation practices for foam sheathing can follow many approaches.  New window step-by-step installation guides have been developed to help the industry follow best practices appropriate for a given window and foam sheathing application.  These guides offer a standard method, a window buck method, a picture frame method and a rainscreen cladding method for mounting window units into walls with exterior foam sheathing or continuous insulation. Taken as a whole, these best-practices help to ensure constructible, code-compliant, durable, and high-performance wall assemblies using exterior foam sheathing for continuous insulation.     

The best approach for a given application with foam sheathing depends on a number of factors:

  • thickness of foam sheathing
  • size or configuration of window
  • whether or not the foam sheathing is used as an approved water-resistive barrier system
  • type of window frame and mounting approach (e.g., integral flange or block frame). 


In addition, the installation must consider an appropriate structural anchorage and support condition for the window unit, as well as an appropriate flashing method to ensure continuity with the water resistive barrier or drainage plane of the wall.

Various successful practices have been employed in design and construction. These approaches are captured in the best-practice guides linked to above as a means to address the conditions of a given application. 

For example, the standard method follows a more traditional installation approach, whereby an integral flanged window unit is installed with the flanges mounted directly over the foam sheathing meeting specifications appropriate for this application.  In particular, the foam sheathing should be minimum 15psi compressive strength rated. This method has been most commonly employed for foam sheathing thickness of about 1-1/2-inches thick or less, though it can be applied for thicknesses of up to 2 inches based on recent testing.

Subsequent articles will explore the step-by-step guides associated with the other best practice installation methods.  

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