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) R-value (insulation) In building and construction, the R-value is a measure of how well an object, per unit of its exposed area, resists conductive flow of heat: the greater the R-value, the greater the resistance, and so the better the thermal insulating properties of the object. R-values are used in describing effectiveness of insulation and in analysis of heat flow across assemblies (such as walls, roofs, and windows) under steady-state conditions. Heat flow through an object is driven by temperature difference (e.g. formula_1) between two sides of the object, and the R-value quantifies how effectively the object resists this drive: