Good humidity control

Abstract

Air-conditioning system designs in hot, humid climates typically use a high level of recirculation owing to the energy penalty involved in cooling and dehumidifying outdoor air. Typical recirculation rates are on the order of 80% to 90% and sometimes higher. While the fundamental focus is indoor humidity level and the means to achieve acceptable RH levels in an energy-efficient manner, it is apparent that adequate ventilation at all times of HVAC operation is strongly dictated by outdoor climatic conditions. If humidity control is addressed, it offers the possibility of enhanced thermal comfort, ventilation and IAQ. It is important to consider humidity issues at design and part loads. This is to prevent buildings from being operated at cold conditions. This is due to the oversized design of AHUs, particularly cooling coils. An oversized coil will tend to provide less dehumidification unless overcooling is used. Since active reheating is not typically permitted for comfort air-conditioning in hot and humid climates due to energy considerations, the buildings stay cold. Comfort air-conditioning in hot and humid climates is usually associated with cold indoor temperatures, relatively high indoor humidity levels, high recirculation rates and often inadequate ventilation.