Material that is used to cover surfaces to reduce heat loss or gain by retarding heat flow through the material. Effectiveness is measured by R-value in units of hr-ft2Â°F/Btu or, in SI, m2Â°C/W. The higher the R-value, the more effective the thermal insulation. For roofs, the maximum thermal conductance (C value) is 0.5 Btu per hr-sq-ftÂ°F (2.8 W per m2 perÂ°C).
The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer. Thermal insulation is the method of preventing heat from escaping a container or from entering the container. In other words, thermal insulation can keep an enclosed area such as a building warm, or it can keep the inside of a container cold.