Which insulation type is most likely to be unfaced?

Unfaced insulation refers to types of insulation products that do not have a vapor retarder or face material on one side. This characteristic makes unfaced insulation particularly useful in scenarios where moisture issues are minimal or where a vapor barrier is not required. It can be employed in various applications, including wall cavities, and attics, where there is a need for thermal resistance without the additional moisture barrier that facings typically provide.

In contrast, foam board, paper-backed insulation, and reflective insulation either include facing materials or have specific functions that do not align with the definition of being unfaced. Foam board insulation typically has a smooth surface on both sides and might require further finishing, while paper-backed insulation is designed specifically with a backing to serve as a vapor barrier. Reflective insulation usually incorporates reflective materials to manage radiant heat and also doesn't fall under the category of unfaced insulation. Thus, the definition and utility of unfaced insulation uniquely apply to the selected answer.