ASTM C518
Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus
What it measures
Measures thermal conductivity by putting a specimen between a hot and a cold plate and reading the heat flow once it is steady. It is the fast, repeatable way insulation R-values are produced.
Why it matters for a panel envelope
Every R-value quoted for an insulation product traces back to a test like this, and the mean temperature it was run at changes the answer.
Guardian Shield™
Shield™ R-values are published at two mean temperatures, which is why the tables give both a 40 °F and a 75 °F column. A 9¼-inch wall panel is R-38 at 40 °F and R-35 at 75 °F.
Source · 3-Part Specification, 1.3 F.10 and 1.5 E.5 b · Guardian documents
Written by Data Subsystems, for Guardian Structural Technologies. Last updated .
Drafted from Guardian Structural product literature and published building-science sources. Awaiting Guardian technical review. Confirm any figure against the current product documents or ask us before you rely on it in a design.