Illinois Roofing Practice Exam

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

1. Through convection

2. Through radiation

3. Through conduction

4. With air spaces or cells in the material

The correct answer is: With air spaces or cells in the material

Rigid board insulation effectively reduces heat transfer in a low-slope roofing system primarily through the presence of air spaces or cells within the insulation material. These air spaces significantly limit the flow of heat because air is a poor conductor of heat. The trapped air within the cells acts as an insulating barrier, minimizing heat loss in winter and heat gain in summer. While convection, radiation, and conduction are all mechanisms of heat transfer, rigid board insulation primarily relies on the effectiveness of trapped air to impede heat movement. Convection typically involves the movement of warmer air rising and cooler air descending, which is minimized in rigid board due to its solid structure. Radiation is the transfer of heat in the form of electromagnetic waves, but solid materials can limit this effect as well. Conduction is the direct transfer of heat through a material, and while insulation reduces conduction, the effectiveness of rigid board insulation is mainly enhanced by its design featuring air spaces that impede all forms of heat transfer.