Polyiso insulation boards on a low-slope roof during a roof replacement, with workers, HVAC units and TPO membrane.

Polyiso Insulation

Component - Polyiso (polyisocyanurate) is an insulation board installed beneath many low-slope roof membranes to improve a roof system’s energy efficiency.

Why Is Polyiso Insulation Used in Roofing?

Polyiso is the most common insulation used in modern low-slope roof systems because it provides more R-value per inch than alternatives like EPS. As one of three primary layers in a commercial roof system, it is frequently discussed when evaluating roof replacement options and energy efficiency requirements.

The thickness of Polyiso influences how effectively the roof resists heat flow. Because Polyiso delivers substantial thermal resistance per inch, it is often used to meet modern energy code requirements.

Polyiso can also be manufactured as tapered insulation. As such, it does more than regulate temperature: it becomes part of the roof’s drainage system by creating slope that moves water toward drains, scuppers and gutters.

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