The thermal resistance of a material is defined by which value?

The thermal resistance of a material is expressed by the R-value. This value quantifies the material's ability to resist heat flow, with a higher R-value indicating better insulating properties. In the context of building and construction, R-values are crucial for evaluating insulation materials and determining energy efficiency. They play a significant role in regulatory building codes, energy performance assessments, and selecting appropriate materials for various applications.

The U-value, which represents the rate of heat transfer and is the inverse of the R-value, is used in different contexts, primarily when talking about the overall thermal performance of a building element (like walls or windows) rather than the material itself. The A-value and T-value are not standard terms used in the context of thermal resistance; thus, they do not apply in measuring or describing a material's resistance to heat flow.