RR-0603: Impact Resistance of Advanced Framed Wall Systems with Insulating Sheathing as the Primary Sheathing

Advanced framed wall systems that use that use a stud spacing of 24 inches on center and eliminate the plywood or OSB sheathing from the wall and replace it with insulating sheathing is a type of enclosure assembly that has been designed to be energy efficient combined with efficient material use. The purpose of this research program was to determine the impact resistance performance of advanced framed wall systems with insulating sheathing as the primary sheathing from wind blown debris. With no standards available for testing wall assemblies, a window industry standard ASTM E1886-05 and E1996-05 Missile Level D, Wind Zone 1 and Wind Zone 2 Enhanced Protection and Wind Zone 3 Basic Protection Standard was adopted was used as a starting point for the research. The testing demonstrated two surprising outcomes: 1. None of the walls passed at an impact velocity of 50 fps including the ½” OSB wall, and 2. The high performance wall assembly (1” of insulating sheathing, housewrap, and 2 inches of closed cell spray foam installed in the cavity space) out-performed the baseline house (framed wall with 1/2” OSB sheathing) at a slightly reduced impact velocity of 43fps. These results indicate that high performance wall assemblies provide equivalent or even better impact performance then standard wall assemblies.