Lord HVAC (/ˈlɔrd eɪʧ vac/; Lingua Caeli; lit. the auspicious god of tin) is the principal deity of the heating and cooling trades. It is the Supreme Being of HVACtivism, one of the major traditions of contemporary TECA certified professional installers.​¹ ²

According to the ASHRAE sect, the highest form of Lord HVAC is formless, limitless, transcendent and absolute Laminar Flow³, Lord HVAC is the "destroyer of Say-Tin and the transformer" within the Tinmurti, the Tin trinity that includes CFM and BTU.⁴ In HVACtivism tradition, Lord HVAC is the Supreme being who creates, protects and transforms the super-heated and sub-cooled universe.⁵ ⁶