Thermal Resistance

What is thermal resistance?

Thermal resistance (R) is a measure of resistance to heat flow through a given thickness of material (also known as R-value). As such, thermal resistance is determined by taking the thickness of a sample and dividing it by its thermal conductivity. Thermal resistivity and R-value are sometimes used interchangeably, however, thermal resistivity differs in that it is a material property (i.e. independent of thickness).

Why is thermal resistance important?

Thermal resistance is specifically used to compare the performance of insulation products. Insulation can take the form of foams, aerogels, or other thermal barrier materials. R-value is often used to quantify single layered samples but can also be applied to layered structures such as those in vacuum insulation panels.

What methodologies are available for thermal resistance testing?

A range of both transient and steady state methods are available for testing at TAL. The Heat Flow Meter (HFM) is considered the gold standard method for determining the thermal resistance of insulation. HFM allows us to measure the thermal conductivity from -10 to 60 °C, and we offer services with multi-temperature point measurements, within ASTM C518-17 specifications (see general HFM design schematic below). The Modified Transient Plane Source (MTPS) is well-suited for a wide range of materials. Specifically, the high-temperature MTPS configuration is ideal for testing insulations used in elevated temperature applications.

Thermal Resistance Testing

We offer MTPS and HFM testing for the thermal resistance of insulation, foams and other materials. Below is a selection of the measurement requirements for thermal resistance testing services.

Recommended Methodologies

Heat Flow Meter (HFM)

Measurement range 0.002 – 1.0 W/mK
Sample size 100 x 100 mm or 300 x 300 mm.
Min. thickness of 5 mm.
Temperature range -10 – 60 °C
Material types Foams, aerogels, polymers and vacuum insulation pannels
ASTM/ISO/EN Standards ISO 8301, ASTM C518, EN 1946-3, EN 12664, EN 12667, EN 12939

High-Temperature Modified Transient Plane Source (HT-MTPS)

Measurement range 0 – 0.150 W/mK
Sample size Min. diameter of 18 mm.
Min thickness is dependent on the thermal conductivity. For materials under 1W/mK, a min. thickness of 1 mm is suggested.
Temperature range 25 – 500 °C
Material types Foams, solids and powders
ASTM/ISO/EN Standards ASTM D7984

Other methods may be available. Contact us at info@thermalanalysislabs.com or call (506) 457-0498 to discuss.

    Contact Us

    Yes, sign me up to receive future emails from C-Therm on new product development, special offers, application information, educational webinars, and published works related to thermal conductivity characterization. You can unsubscribe at any time. Subscription is optional.