When evaluating the effects of hail on single-ply roofing, an important consideration is how hail might have affected the underlying insulation. Given the substantial hail resistance of many single-ply roofing membranes, it is possible for hail to dent the underlying insulation without damaging the roofing membrane. The absence of hail-caused damage to the membrane can reassure the property owner that the water-shedding ability of the roof has not been compromised. But will the owner incur noticeable increases in energy bills because the thermal performance of the roof insulation is reduced?

To address this question, Haag studied the effects that dents have on the thermal performance of roof insulation. Thermal resistance of common roof insulations, including polyisocyanurate (polyiso), extruded polystyrene (XPS), expanded polystyrene (EPS), and perlite, were measured in dented and nondented configurations. The thermal resistance of the insulation was then compared to the extent of denting. The research findings are most applicable to single-ply roofing systems because most other roofing types are rigid enough to protect the underlying insulation from being dented by hail.

Download the technical paper to explore the research findings.