Assessment of Thermal Bridging of Fasteners through Insulated Roof Assemblies

Roof fastener systems are comprised of metal screws and plates used to attach roof membranes, cover boards, and insulation. These systems can have an adverse impact on the thermal performance of roof assemblies, as the components create thermal bridges that bypass the thermal resistance of insulation in the roof assembly. This in turn allows heat to escape at an accelerated rate, flowing outward in cold weather and inward in warm weather. While the thermal performance of 3-D thermal bridges can be numerically simulated with software tools, such simulations are time-consuming and need to be verified by laboratory tests to validate the underlying assumptions made during the simulation.

During this presentation, participants will learn how the research team used a series of laboratory tests to compare the thermal performance of physical models of simple roof assemblies under controlled laboratory environmental conditions with computer simulations of the same conditions. Assemblies were comprised of high-density polyisocyanurate cover board, polyisocyanurate insulation, and steel deck, tested both with and without #12 and #15 fasteners and plates. In this session, the results of both physical models and computer simulations are presented and compared. The outcome is an experimentally validated computer simulation approach that will enable consultants to evaluate a broader range of roof assemblies and roof fastener configurations.