Advanced HVAC Humidity Control for Hot-Humid Climates: U.S. Department of Energy (DOE), Energy Efficiency & Renewable Energy (EERE)

Managing indoor humidity is challenging and more important than ever for new, energy efficient homes equipped with whole-house mechanical ventilation, particularly during part-load and shoulder season conditions. Newer homes with higher levels of insulation, more efficient windows, and tighter building envelopes have less heat gain during the cooling season, but the moisture/humidity related loads tend to remain about the same, despite tighter construction practices that reduce infiltration of humid outdoor air. The moisture loads (referred to as latent loads, distinguished from temperature related heat gains that are referred to as sensible loads) may even be higher due to whole-house mechanical ventilation requirements. The result is that latent loads are proportionately greater relative to total loads (sensible plus latent loads) for more efficient homes, particularly during part-load conditions - periods with lower outdoor temperatures than peak-load design temperatures. To illustrate this challenge, the image below, developed by Home Innovation, shows latent loads as a percentage of total air conditioning loads for an example energy efficient home compared to a standard, less efficient home, for peak-load and part-load conditions. For efficient homes, typical air conditioning systems will satisfy the thermostat before running long enough to properly dehumidify the house, particularly during part-load periods.