H

heat exchanger a device used to transfer heat, often through coiled tubing, from one fluid to another.
heat island effect the rise in ambient temperature that occurs over large built up and paved areas. strategic placement of trees can reduce this effect and reduce energy consumption for cooling by 15-30%.
heat load the total energy needed for space heating.
heat loss the amount of heat lost through the building envelope, e.g. walls, windows, roof, floors, doors.
heat pump a device to transfer heat from a heat source to a heat sink. as the heat source cools it transfers heat to the sink which then warms up.
heat pump a mechanical device used for heating and cooling which operates by pumping heat from a cooler to a warmer location. heat pumps can draw heat from a number of sources, e.g., air water or earth and are classified as either air, water or ground source units.
heat recovery ventilator exhaust fans that warm the incoming air with the heat from the outgoing air, recovering about 50-70% of the energy. in hot climates the function is reversed so that the cooler inside air passes by the incoming hot air and reduces its temperature.
heat transfer the transfer of heat is normally from a high temperature object to a lower temperature object. heat transfer changes the internal energy of both systems involved according to the first law of thermodynamics.
heating, ventilating and air conditioning (hvac) the mechanical systems that heat, cool, ventilate, filter, humidify or treat air in buildings.
hydrochlorfluorocarbon (hcfc) hydrochlorfluorocarbons or hydrogenated chlorofluorocarbons are used as a substitute for cfcs, as they are less destructive to ozone, although less efficient as refrigerants and sometimes quite toxic.
hydroflourocarbon (hfc) a compound consisting of hydrogen, fluorine and carbon. hfcs do not deplete stratospheric ozone, but they have global warming potentials anywhere from 90 to 12 000 times that of carbon dioxide.
hygroscopic a material that attracts moisture from the atmosphere.