The term R-value is used to describe what aspect of insulation materials?

The term R-value refers specifically to the thermal resistance of insulation materials. It quantifies how well a given material can resist the flow of heat. The higher the R-value, the better the insulation's effectiveness at reducing heat transfer, which is crucial for maintaining energy efficiency in a building. This aspect is essential in building physics as it directly influences heating and cooling needs, ultimately impacting energy costs and comfort levels within structures. Understanding R-value helps inspectors evaluate the adequacy of insulation in attics and other areas, ensuring that buildings are properly insulated for temperature control.