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) Especially in older or historic buildings the R-values defined before construction might be very different than the actual values. This greatly affects energy efficiency analysis. To obtain reliable data, R-values are therefore often determined via U-value measurements at the specific location (in situ). There are several potential methods to this, each with their specific trade-offs: thermography, multiple temperature measurements, and the heat flux method. Thermography is applied in the building sector to assess the quality of the thermal insulation of a room or building. By means of a thermographic camera thermal bridges and inhomogeneous insulation parts can be identified. However,