The ASTM accelerated aging test method for unfaced foamboard insulation that is based on slicing and scaling has been used on an extruded polystyrene product blown with HCFC-142b. The test method including specimen preparation was carried out at three laboratories. The participating laboratories used different means to prepare thin test specimens. Thin slices of foamboard with and without surface skins were tested in order to assess the effect of skins on the aging process.

Measured values for the apparent thermal conductivity, k^a, were used to calculate time average k^a for life-times of 10, 20, and 40 years. The time-average k^a, from the three laboratories differed by less than 2.5% for 1.5-inch-thick product and less than 2% for 2.0-inch-thick product. The k^a for slices with skin on one surface were less than k^a of slices of the core foam.