CASE COMMENT: We are looking for clarification regarding Section 504.5 which requires ducted heat recovery ventilators to comply with UL 1812. We are looking to utilize a ducted heat recovery ventilator, but it complies with UL 1995 which appears to be more strict (55 tests vs. 25 tests) than UL 1812. UL 1995 appears to contain nearly all of the tests that UL 1812 has. UL 1812 appears to be more focused on smaller type units more suitable for residential applications while UL 1995 is more focused on larger, commercial style HVAC equipment (which we are proposing to use in this instance). RESPONSE: UL 1995 is not acceptable as a more stringent substitute for UL 1812. Section 504.5 of the 2024 Uniform Mechanical Code only states UL 1812. UL Standard 1812 is specifically applicable to ducted heat recovery ventilators, whereas UL Standard 1995 has a much broader application as it references HVAC in general. The criteria of UL 1812 includes construction and performance standards for equipment listed for outdoor-use where UL 1995 does not.