The R-Value Test

May 29, 2014   -  

Focus On: The R-Value Test

Thermal conductance is the time rate of steady-state heat flow through a unit area of a material induced by a unit temperature difference. Experimentally, to measure the thermal conductance of a material, place a test specimen between two parallel plates at constant but different temperatures and measure the steady state one-dimensional heat flux through the specimen.

Screen Shot 2021-09-29 at 11.29.20 AMThe inverse of thermal conductance is thermal resistance. Thermal resistance is the ability of a material to resist the flow of heat. In the building and construction industry, R-Value is a measure of thermal resistance. Under steady state conditions, it is the ratio of a temperature difference (ΔT) across a material and the heat flux (Q) flowing through it.

R = ΔT / Q

Here at NGC Testing Services, we test in accordance with ASTM C 518 to determine R-Value of materials utilizing the principles as illustrated.

What Do Those Letters Mean?


Any laboratory you utilize should be accredited. Be sure to check a lab’s scope of accreditation (list of tests it is accredited for) by looking under its lab code for that accreditation or listing. At NGC Testing Services, we are proud of our accreditations, which we believe are most preferred in the industry for the testing services we provide.

Gaining and maintaining accreditations requires a significant amount of effort, which includes establishing a comprehensive quality system, collection of data, and periodic in-depth, on-site assessments. NGC Testing Services Laboratories’ Accreditations include:

NVLAP Accredited

Lab Code: 200291-0

NVLAP or the National Voluntary Laboratory Accreditation Program is administered by the National Institute of Standards and Technology (NIST), part of the U.S. Department of Commerce.


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IAS Accredited

Testing Laboratory 216

IAS or International Accreditation Service (IAS) is a subsidiary of the International Code Council (ICC)

City of New York, MEA

Acceptance Laboratory - No. 102-01-L

California State Fire Marshal (OSFM)

Approved Testing Laboratory

Florida Building Commission

Approved Product Testing Laboratory

UL's Third Party Test Data Program (TPTDP)

Acoustical Testing - File DA1294

ISO/IEC 17025 Compliant

This is the basic requirement utilized by most laboratory accreditation organizations. Issued by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC), it is the single most important standard for calibration and testing laboratories around the world. Laboratories that are accredited to this international standard have demonstrated that they are technically competent and able to produce precise and accurate test and/or calibration data.

Mutual Recognition Arrangements

In addition, there are Mutual Recognition Arrangements (MRA) among accreditation bodies around the world that include NVLAP and IAS, our primary accreditations. Two MRAs are APLAC (Asia Pacific Laboratory Accreditation Cooperation) organization and ILAC (International Laboratory Accreditation Cooperation).NCG Testing Contact Us CTA_v1


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NGC Testing Services features one of North America's most sophisticated and unique fully accredited testing facilities. Contact us today to visit our 50,000 plus square-foot facility located in Buffalo, New York.