The operation of standard vapor-compression cooling systems involves the reduction, not the increase, of moisture content within a conditioned space. This is because these systems cool air below its dew point temperature. As air passes over the cold evaporator coil, water vapor condenses into liquid water, which is then drained away. This process effectively removes moisture from the air, leading to a decrease in relative humidity. An analogy can be drawn to a cold beverage on a humid day: condensation forms on the outside of the glass as moisture from the air is cooled and converted to liquid.
Maintaining appropriate humidity levels is crucial for comfort, health, and the preservation of building materials. Excessive humidity can foster mold growth, exacerbate respiratory problems, and damage structures. By extracting moisture, cooling systems contribute to a healthier and more comfortable indoor environment. This moisture removal capability has been a key feature of air conditioning technology since its inception, initially designed to address issues of paper warping in printing plants due to high humidity.