ASTM C578
Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation
What it measures
Classifies rigid polystyrene insulation into types by density and sets the minimum thermal resistance, compressive resistance, water absorption and dimensional stability each type must meet. It is the specification that lets an architect write "Type I EPS" and know exactly what will arrive.
Why it matters for a panel envelope
The EPS core is the insulating half of a Shield™ panel and the web of its I-beam action, so its grade governs both the R-value and how the panel carries load.
Guardian Shield™
The Shield™ system uses UL certified modified expanded polystyrene with a minimum density of 0.90 pcf, Type I, complying with ASTM C578.
Source · 3-Part Specification, 1.3 F.11 and 1.5 E.5 · 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.