Installation and Performance of Flanged Fenestration Units Mounted on Walls with Foam Plastic Insulating Sheathing

Research Report No.: 
Issue Date: 
Wednesday, April 7, 2021 - 07:15
Update Date: 
Wednesday, May 19, 2021 - 07:15

This report assesses construction practices, codes, standards, and performance test data related to the installation of flanged fenestration units on walls with foam plastic insulating sheathing (FPIS) serving as continuous insulation (ci). A key objective is to determine appropriate limitations to the historically accepted practice of installing flanged fenestration units directly over FPIS ci (i.e., mounting flanges bearing on and fastened through foam sheathing). Understanding the historically accepted practice and knowing its limitations based on actual performance also will serve to better delineate where enhanced installation procedures may become advisable or necessary. Based on the findings reported herein, a standard installation practice is recommended achieve the above-described objective. The proposed standard practice includes performance-based (e.g., testing) and prescriptive installation requirements. The performance-based approach offers the greatest flexibility to qualify acceptable installation methods. The prescriptive installation requirements represent a refined and limited application of historically accepted installation practice.