The AAMA/FMA/WDMA Installation Method Coordination Committee met October 14-15 in Chicago to ballot comments to the latest draft, provisionally titled Standard Practice for the Installation of Windows into Walls Utilizing Foam Plastic Insulating Sheathing [FPIS].The essence of the document is to address water management concerns at the rigid insulating sheathing and window interface.The practice addresses scenarios in which the FPIS may be installed over a separate Water Resistive Barrier (WRB) layer, or under a separate WRB and the resulting water management considerations. The FPIS referenced in this standard practice is being used for its thermal value; not as an air barrier, drainage plane, structural window support or structural sheathing.
The committee used the October sessions to overview the new installation document, with the general focus being to add and clarify illustrations and terminology.
Different methods of installation are available to accommodate windows placed directly in the opening or installed utilizing a Rough Opening Extension Support Element (ROESE) – much like a picture frame – and the sequencing of component installation. The function of the ROESE is to support the weight of the window and to enable window alignment with the exterior plane of the FPIS for ease of integration with cladding and/or WRB.
Each of the three basic installation methods described (A, B and C) allow for the window to be installed before or after the WRB. The choice of installation methods will rely on the construction sequencing and the alignment of the window with the interior and exterior façade. Component selection is critical to the installation aligning correctly to properly address water management concerns at the rigid insulating sheathing and window interface.
- Method A describes a window that is installed such that the mounting flange is in the plane of the structural sheathing and the FPIS is installed interior to the WRB. The window may be installed before or after the WRB, and may be recessed relative to the FPIS.
- Method B describes a window that will be installed into a ROESE and the FPIS is exterior to the WRB. This Method requires installing the window after the WRB.
- Method C actually consists of two options. Neither utilizes a ROESE and the FPIS is exterior to the WRB. This method allows installation of the window before or after the WRB. Method C1 applies when the window is outboard of the FPIS by at least three-quarters of an inch; Method C2 is used when the window is less than three-quarters of an inch outboard of the FPIS or recessed relative to it.
Each method includes diagrams to illustrate which layer is operating as the WRB. Committee technical concerns revolved around water barrier vs. drainage approaches, resolving to address both in an appendix.
The methodology wraps up with a description of how to apply interior air/water seal and post-installation procedures.
Concerns to be resolved regarding installation Method C took note of the lack of language in the document about creating drainage space between foam and WRB.
Also discussed is the need for more details for situations where thicker FPIS is to be used. Window integration to the WRB and exterior nose of window to cladding needs to be well detailed.
Efforts to simplify instructions for determining the correct window size, given different interior and exterior conditions, are also being considered, such as the simplicity of “measure inside/outside, get the right window, and make sure it will work with both inside and outside conditions.”
Adding cautionary statements and disclaimers regarding unexpected conditions that might be encountered are also being discussed. A more detailed “decision tree” approach to determining installation issues based on wall conditions and their resolution may be added as well.
The committee will continue with conference call meetings leading up to in-person sessions at the February, AAMA 78th Annual Conference.