Latent Heat
Latent heat is thermal energy associated with the phase change of water (vapor → liquid → ice) without changing temperature. In HVAC, latent heat shows up as humidity: the AC unit must condense water vapor on its evaporator coil to dehumidify, and that condensation releases ~970 BTU per pound of water. In humid climates, latent load can be 30-50% of total cooling load. ERVs recover latent heat in winter (humidifying outgoing air) and summer (limiting incoming moisture).