habitable space:

hearth: the floor within a fireplace.

hearth extension: non-combustible material in front of and at the sides of a fireplace opening.

heat-welded: Also referred to as heat-seaming, it is the process of joining and sealing overlapping thermoplastic membrane edges with heat.

heated slab: slab-on-grade construction in which the heating elements are placed within or under the slab.

HEPA: High efficiency particulate arrestance (filters).

hip: The external angle formed by the meeting of two sloping sides of a roof.

hood: a device that directs and captures grease-laden vapors and gases from a cooking appliance.

humidistat: a device used to automatically control relative humidity.

HVAC: Heating, ventilation, and air-conditioning system.

hypersensitivity diseases: Diseases characterized by allergic responses to animal antigens. The hypersensitivity diseases most clearly associated with indoor air quality are asthma, rhinitis, and hypersensitivity pneumonitis. Hypersensitivity pneumonitis is a rare but serious disease that involves progressive lung damage as long as there is exposure to the causative agent.