1 SCOPE
1.1 This procedure defines the long-term thermal resistance (LTTR) of a foam product as the value
measured after 5-year storage in a laboratory environment and provides means for its prediction based
on an accelerated laboratory test.
1.2 This procedure, based on ASTM standard test methods ASTM C1303 and ASTM C518, can be
applied to a wide range of preformed as well as field manufactured insulating foams. This procedure
estimates the change in the thermal resistivity of insulating foam products by means of slicing and scaling.
1.3 This procedure addresses faced and unfaced products without consideration to the effect of facers
on the LTTR of the product.
NOTE: This method is not intended for products with impermeable membranes such as those with sheet metal facers,
which will retain most of their initial R-values. Reference: M.A. Kabayama, Long-Term Thermal Resistance Values of
Cellular Plastic Insulations.
1.4 This test procedure is applicable to cellular plastic insulation manufactured to retain a gas or mixture
of gases, other than air, for a period longer than 180 days. If the thermal resistivity of a product changes
by more than 3 % over this 180 day period, this test procedure shall be applied. This procedure specifies
reference time, sampling and testing requirements and is based on ASTM standard test method
ASTM C1303 to determine LTTR for closed-cell foams such as extruded polystyrene, sprayed
polyurethane, and polyisocyanurate.
1.5 This procedure does not purport to address all the safety concerns, if any, associated with its use. It
is the responsibility of the user to establish appropriate safety and health practices and determine the
applicability of regulatory limitations prior to use.