ASTM C518 Thermal Transmission Properties

Standard: ASTM C518 Standard Test Method for Steady-State Thermal Transmission Properties by means of the Heat Flow Meter Apparatus 

Scope: This test method covers the measurement of steady-state thermal transmission through flat slab specimens using a heat flow meter apparatus. The heat flow meter apparatus is used because it is relatively simple in concept, rapid, and applicable to a wide range of test specimens. The precision and bias of the heat flow meter apparatus can be excellent, provided calibration is carried out within the range of heat flows expected. Calibration should be done with materials that are similar to the ones being tested, and the properties of the calibration specimens must be traceable to an absolute measurement method.

Products: Many different products can be tested per ASTM C518, including, but not limited to: insulation materials such as spray foam, polyiso. board, polystyrene board, cellulosic fiber board, and batt insulation; as well as other construction materials.

Procedure: The heat flow meter apparatus is comprised of a hot plate and a cold plate. The product is placed between the two plates, and the test equipment measures the heat flow from the hot plate through the product and the cold plate. The measured resistance of heat flow between the two plates is the product’s thermal resistance or R-value.

Result: The thermal conductivity (k-value) and thermal resistance (R-value) are determined and are used to determine energy losses through a material.