Closed-cell Spray Polyurethane Foam: Shrinkage and How to Manage It

Closed-cell spray polyurethane foam (ccSPF) insulation is used in exterior roof and wall assemblies to effectively combine air/vapor/thermal barrier and sometimes weather barrier. A critical aspect of ccSPF is it can undergo post-installation dimensional changes that are problematic when they result in breaches of the intended barriers. This article discusses conditions that lead to ccSPF shrinkage and separation from substrates and strategies to mitigate them.
ccSPF is always combined with other functional components of the wall or roof assembly (e.g. water barrier, structural framing, ignition barrier, etc.) to create an effective, durable, and building code-compliant assembly. These components and their effect on building performance are outside the scope of this article. Similarly, open-cell spray polyurethane foam (ocSPF) is used in building envelope assemblies as an air and thermal barrier. It has different performance and technical characteristics than ccSPF and is also not addressed here.
Publisher
Construction Specifier