HVAC: acronym for Heating, Ventilating, and Air Conditioning.
Hatch: a unit used to provide access to a roof from the interior of a building.
Headlap: the distance of overlap measured from the uppermost ply or course to the point where it laps over the undermost ply or course.
Holiday: an area where a liquid-applied material is missing or absent.
Hybrid roof covering: combination of two or more separate and distinct roof membranes; e.g. three ply smooth BUR and a modified bitumen cap.
Hypalon: a trademark for chlorosulfonated polyethylene (CSPE) synthetic rubber (CSM) noted for its resistance to chemicals, temperature extremes and ultraviolet light. It was a product of DuPont Performance Elastomers, a subsidiary of DuPont.