R-value is a term preominantly used in the building industry to describe the insulation properties of certain building insulation materials. Its use is limited to situations where thermal insulation is achieved by retarding the flow of heat through the material itself rather than reflecting radiant heat away. The higher the R-value, the greater the insulation. Although they offer a useful means of comparing the performance of different products, other factors need to be considered in maintaining thermal comfort (see building insulation).