In roof assemblies, what is the role of foil-faced insulation boards?

• A. They serve as a reflective layer to reduce radiant heat transfer and are not intended to be the sole insulation.
• B. They provide the primary structural support for the roof.
• C. They are only used for decorative purposes.
• D. They are used to seal joints in the foundation.

Answer: (C)

Foil-faced insulation boards mainly act as a radiant barrier in roof assemblies. The shiny foil reflects a large portion of radiant heat away from the living space, helping to keep attics cooler in hot weather and reducing heat gains indoors. This reflective layer adds to the board’s overall insulation, but it isn’t meant to be the sole insulation or the primary structural support for the roof. The structural role comes from the roof framing and decking, not the foil-faced boards. They aren’t decorative, and they don’t seal joints in the foundation. For best performance, install the foil facing so it can reflect heat effectively (often with an air gap as designed) and ensure seams are properly sealed. In short, these boards contribute to reducing radiant heat transfer and boosting insulation as part of a complete roof assembly, not as a decorative feature, a structural element, or a foundation sealant.