Thermal Resistance

a measure of heat resistance

Definition of Thermal Resistance

A measure of any material’s ability to resist heat transfer. It’s often described as the temperature difference across an object and the rate of heat flow through it.

The SI unit of thermal resistance is Kelvin per watt, usually depicted as K/W or degrees Celsius per watt °C/W. Kelvin (K) is the unit measurement of temperature while Watt (W) depicts power.

A material that has a high thermal resistance means it requires more energy to allow heat to move through it.

Typically, a material’s thermal resistance depends on its material, thickness, and structure (shape). Thicker materials have a high thermal resistance.

Additionally, the surface area and temperature difference from one end to another influences thermal resistance.

Thermal resistance can also be defined as the reciprocal of thermal conductivity, where thermal conductivity is the ability of a material to conduct heat.

If a material has a low thermal conductivity, it means it has a high thermal resistance—it has a high opposition to heat flow.

On the other hand, a material with high thermal conductivity has a low thermal resistance i.e., it allows heat to pass easily.

This explains why a material like alder, with low thermal conductivity—thereby preventing overheating—is used to make sauna benches.

A metal would have a low thermal resistance, allowing heat to pass easily and causing burns when touched.

Finally, thermal resistance is also related to R-value, where the R-value highlights the thermal resistance of materials used to provide insulation.

calculating thermal resistance

Example of “Thermal Resistance” in a Sentence

When buying an at-home sauna, choose one with a high thermal resistance.

Related Terms for Thermal Resistance