Although SIPs are available with either a Polyurethane (PUR) foam core or Expaned Polystyrene (EPS) core, we think PUR foam is a far better insulator and offers the best physical properties of any available insulating foam.
R-Value. Polyurethane has a stable R-value of R-7 per inch of thickness, so you can achieve at least an R-25 with typical 4.5" walls.
Fire. SIPs are tested to the ASTM E84-04 “Standard Test Method for Surface Burning Characteristics of Building Materials” for smoke and flame spread. The polyurethane foam core has a Class 1 fire rating with a flame spread less than 25 units and smoke spread less than 400 units.
Foam Properties. Unlike some blowing agents, a number of which are scheduled for phase-out by the Environmental Protection Agency (EPA), PUR foam is not a volatile organic compound and, hence, does not contribute to ozone depletion.
Additional benefits of the polyurethane core:
Compared to other types of PUR, HFC-245fa polyurethane foam offers the best insulation and protection against moisture transport due to its density, cell structure, and good adhesion to skins. HFC-245fa polyurethane foam is used in the manufacture of Greenix Panels.
