What function does insulation have in a roofing assembly?

Insulation plays a critical role in a roofing assembly primarily by enhancing thermal efficiency and moisture control. By reducing heat transfer between the interior of a building and the external environment, insulation helps maintain comfortable indoor temperatures and reduces energy consumption for heating and cooling. Properly installed insulation can also prevent condensation and moisture-related issues, such as mold growth and structural damage, by controlling the movement of vapor and keeping areas dry.

While insulation may indirectly contribute to aesthetic appeal by enabling different roofing designs or systems, and while it can support installations like solar panels through added structural support or appropriate layering, these are not its primary functions. Similarly, insulation is not designed to offer structural reinforcement; that function typically falls to materials such as decking and framing components. Therefore, the enhancement of thermal efficiency and moisture control is the key function of insulation in roofing assemblies.