What does "R-value" measure in insulation materials?

R-value measures the thermal resistance of insulation materials, indicating how well a material can resist heat flow. The higher the R-value, the better the insulation's effectiveness in maintaining temperature and energy efficiency within a building. This measurement is crucial for evaluating insulation options for walls, attics, floors, and other building components, as it helps determine how well a structure will retain heat during colder months and keep cool air in during warmer months.

In contrast, the other options pertain to different characteristics of materials. The density of the material and its weight do not directly relate to its ability to insulate, and moisture content, while affecting insulation performance, is not what R-value quantifies. Thus, emphasizing the thermal resistance aspect encapsulates the core purpose of R-value in the context of insulation.