The EPS Industry Alliance publishes technical bulletins to help inform building professionals on the performance characteristics of expanded polystyrene (EPS) building products. The information contained herein is provided without any express or implied warranty as to its truthfulness or accuracy.
The Expanded Polystyrene Association of Canada (EPAC) conducted a joint research project with the National Research Council of Canada/Institute for Research in Construction (NRC/IRC) to evaluate the durability performance of expanded polystyrene (EPS) insulation in an exterior below‐grade application.1 EPS insulation, thermal performance, site weather conditions and soil moisture content were instrumented and monitored throughout the project.
The in‐situ thermal performance of the EPS insulation was monitored over a 30‐month exposure period using thermal couples attached to EPS insulation and the concrete wall. The monitoring of thermal performance detected the presence of water at the outer surface of the EPS foam during periods of heavy rain and major thaws; however, the surface of the concrete basement wall showed no evidence of water penetration through most of the height of the wall.
In addition, material properties for EPS insulation removed after the 30‐month exposure were determined. Testing confirmed that all types of EPS insulation retained their specified thermal and mechanical properties even after being subjected to in‐situ freeze‐thaw cycling. The moisture content of EPS insulation samples removed after the 30‐month exposure was in the range of 0.01 to 0.96% by volume.
Key issues highlighted from the 30‐month field exposure period of the research project include:
A second part of the research project included development of a durability test protocol that subjected test material to extreme thermal gradient and environmental cycling, including freeze‐thaw cycling.2 Testing performed by NRC on samples of the same material that was subjected to the 30‐ month field exposure confirmed that all types of EPS insulation retained their specified material properties even after being subjected to the durability test protocol. The NRC test protocol was subsequently developed into an ASTM standard test method to provide a means of assessing durability performance of all types of insulation.3