ULC 770 2025

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.
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.
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.
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.
This procedure specifies reference time, sampling and testing requirements and is based on test method ASTM C1303 to determine LTTR for closed-cell foams such as extruded polystyrene, sprayed polyurethane, and polyisocyanurate.
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.