Thermal conductivity common use in the construction and textile industries. The construction industry makes use of units such as the R-value (resistance) and the U-value (transmittance). Although related to the thermal conductivity of a material used in an insulation product, R- and U-values are dependent on the thickness of the product. Likewise the textile industry has several units including the tog and the clo which express thermal resistance of a material in a way analogous to the R-values used in the construction industry. There are a number of ways to measure thermal conductivity. Each of these is suitable for a limited range
R-value (insulation) +43° C (110° F). Nevertheless, in construction it is common to treat R-values as independent of temperature. Note that an R-value may not account for radiative or convective processes at the material's "surface", which may be an important factor for some applications. The R-value is the reciprocal of the thermal transmittance (U-factor) of a material or assembly. The U.S. construction industry preferes to use R-values, however, because they are additive and because bigger values mean better insulation, neither of which is true for U-factors. The "U-factor" or "U-value" is the overall heat transfer coefficient that describes how well a building