ASTM C518

ASTM C518 is a standard test method for measuring the steady-state thermal transmission properties of insulation materials using a heat flow meter apparatus. This test method is used to determine the thermal conductivity and resistance of insulation materials, such as foams, fibers, and rigid boards, under steady-state conditions.

TRUSTED BY ENGINEERS FROM

ASTM C518 Introduction

ASTM C518 testing is a standardized method for determining materials’ steady-state thermal transmission properties using a heat flow meter apparatus. It evaluates a material’s ability to resist heat transfer, making it an essential tool for many industries. By quantifying a material’s thermal insulation properties, the ASTM C518 test helps select appropriate materials for energy-efficient designs and products.

Scope of ASTM C518

The ASTM C518 test method applies in general to fully processed types of materials, including but not limited to building materials, insulation products, and composite structures. Desirable characteristics of thermal conductivity and resistance are developed during processing. The final values of the procedure are stated in standard units of SI. Testing can also be through having the material between a hot plate and a cold plate with heat flux transducers in between to physically show how the internal heat of the material is transferring from one plate to another. The test shall ascertain the steady-state thermal conductivity measurement of various materials of variable conductivity levels and thickness.

The most typical application of this test is to determine precisely how effective insulation is. The test can produce an R-value and a K-value (thermal conductivity) (thermal resistance). These measures allow you to show consumers how a specific material may be superior to others as insulation while also proving that it complies with federal rules for insulation materials.

ASTM C518 Test Procedure

This testing procedure involves placing a specimen between two plates in a heat flow meter apparatus. One plate is heated while the other is cooled, creating a controlled temperature gradient across the specimen. Heat moves from the heated to the cooled plate through the sample. The temperature differential and the rate of heat movement are measured to determine the specimen’s thermal conductivity, thermal transmittance, and thermal resistance.

Other Typical Tests Conducted Using ASTM C518

This test method can evaluate the thermal conductivity and thermal resistance characteristics of materials such as windows and other construction materials, in addition to insulation. In some circumstances, the ASTM C518 may be preferable to the ASTM C177. In the ASTM C177 test, a guarded hot plate apparatus replaces the heat flow meter apparatus.

ASTM C518 Test Specimens

The following are some of the specimen details of the standard test:

Sample details	ASTM C518 test method applies to a wide range of materials, including building materials, insulation products, and composite structures.
Sample dimensions	The acceptable specimen dimensions for ASTM C518 are at least 150 mm x 150 mm (6 in. x 6 in.) with a thickness of at least 25 mm (1 in.).
Sample preparation	Before testing, the test specimens are prepared as per the manufacturer’s instructions and conditioned to the proper temperature and humidity levels.

ASTM C518 Test Data

The test provides valuable information about a material’s thermal performance. The results obtained include:

Thermal conductivity: Indicates how effectively the material conducts heat.
Thermal resistance: This signifies the material’s ability to resist heat flow.
Thermal transmittance: Characterizes the overall heat transfer through a construction assembly.

ASTM C518 Test Conclusion

ASTM C518 is a vital test method for measuring insulation materials’ steady-state thermal transmission properties using a heat flow meter apparatus. This standard provides detailed guidance on the test conditions, sample preparation, measurement procedures, and reporting requirements for accurately determining insulation materials’ thermal conductivity and resistance.

FAQs on ASTM C518 Test

What is ASTM C518?

The ASTM C518 test provides valuable information about a material's thermal performance. The results obtained include Thermal conductivity, which indicates how effectively the material conducts heat, and thermal resistance, which signifies the material's ability to resist heat flow.

What size specimen is ASTM C518?

Specimens of ASTM C518 should have a parallel surface with a size of 150-300 mm2.

What is the temperature range for ASTM C518?

The method has been used at ambient conditions of 10 to 40°C with thicknesses up to approximately 250 mm and with plate temperatures from –195°C to 540°C at 25-mm thickness.