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Title: Technology Solutions Case Study: Application of Spray Foam Insulation Under Plywood and OSB Roof Sheathing

Spray polyurethane foams (SPFs) have advantages over alternative insulation methods because they provide air sealing in complex assemblies, particularly roofs. Spray foam can provide the thermal, air, and vapor control layers in both new and retrofit construction. Unvented roof strategies with open cell and closed cell SPF insulation sprayed to the underside of roof sheathing have been used since the mid-1990s to provide durable and efficient building enclosures. However, there have been isolated incidents of failures (either sheathing rot or SPF delamination) that raise some general concerns about the hygrothermal performance and durability of these systems. The primary risks for roof systems are rainwater leaks, condensation from diffusion and air leakage, and built-in construction moisture. In this project, Building Science Corporation investigated rain and built-in construction moisture and vapor drives. Research involved both hygrothermal modeling of a range of rain water leakage scenarios and field evaluations of in-service residential roofs. Other variables considered were climate zone, orientation, interior relative humidity, and the vapor permeance of the coating applied to the interior face of open cell SPF.
Publication Date:
OSTI Identifier:
Report Number(s):
Research Org:
Building Science Corporation (BSC)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Building Technologies Office (EE-5B) (Building America)
Country of Publication:
United States
residential; Residential Buildings; Building America; BSC; spray foam; open cell; closed cell; plywood; OSB; roof; roof sheathing; hygrothermal modeling; moisture content