Latent heat is the thermal energy absorbed or released when a substance changes state, such as from liquid to gas, without changing its temperature. In HVAC applications, latent heat load represents the energy required to remove or add moisture from indoor air. This differs from sensible heat, which changes air temperature without affecting humidity levels.
Latent vs. Sensible Load
Typical buildings experience latent heat loads of 20 to 50 percent of total cooling requirements, depending on occupancy and ventilation rates. In humid climates or crowded spaces, latent loads can reach 60 percent of total cooling demand. Proper dehumidification requires equipment sized to handle both sensible and latent cooling, often at 95°F outdoor temperature with 75 percent relative humidity.
System Design Significance
HVAC systems must remove latent heat to maintain comfort and prevent moisture-related problems like mold and material degradation. Undersized systems fail to dehumidify adequately, leaving indoor spaces feeling clammy at 75°F. Technicians use psychrometric charts and load calculations to ensure equipment capacity addresses latent cooling requirements alongside temperature control.