How does rigid board insulation reduce heat transfer in a low-slope roofing system?

Rigid board insulation effectively reduces heat transfer in a low-slope roofing system primarily because it creates a solid thermal barrier between the outside and the inside. This type of insulation is designed to resist heat flow, maintaining a stable indoor temperature regardless of outdoor conditions. The solid structure of rigid board insulation limits the movement of heat through conduction, which is crucial in preventing heat from entering the building during hot weather or escaping during colder months.

While the option regarding air spaces or cells could theoretically contribute to insulation properties, rigid board insulation relies more on its solid, dense nature and the materials used, such as polystyrene or polyisocyanurate, that inherently have low thermal conductivity. This means that the insulation prevents heat transfer more effectively than relying on trapped air or empty spaces within the material. When discussing thermal barrier effectiveness, it’s the continuous, rigid nature of the board that primarily serves to minimize thermal bridging, making it a better option in this context for providing insulation against heat transfer.

Understanding the physical principles behind how rigid board insulation functions emphasizes that it is the material properties, rather than just the presence of air spaces or cells, that predominantly govern its role in effective thermal insulation in roofing applications.