Why Don't A/Cs Work in High Humidity?

Air Conditioners and Humidity

• Air conditioners cycle on and off to maintain a consistent, user-defined indoor temperature. Because air conditioners circulate so much air throughout the home, they often decrease relative humidity. But if an air conditioner fails to do this, the home can quickly become uncomfortable since high relatively humidity will give the impression that the air conditioner is not working to cool the home. Air conditioners, when used properly, actually decrease indoor humidity levels, so if the indoor humidity levels seem high, the problem can usually be resolved.

Air Conditioner Size

• Using an air conditioner that is too large for your home is a common cause of the unit's failure to reduce indoor humidity. A large air conditioner will cycle on when temperatures go above the thermostat's setting but will quickly cycle off when temperatures drop. This frequent, brief cycling on and off can lower the air temperature in a home without lowering the relative humidity inside the home. To avoid or correct this problem, find out what the ideal-size air conditioner for your home is before installing or replacing an air conditioner unit.

Window Units

• The very design of some window unit air conditioners can contribute to indoor humidity problems. Swamp coolers draw air inside the home and pass it through a wet medium such as a sponge to cool the air down. Because the air coming out of the air conditioner is damp, swamp coolers can greatly increase the humidity in a room and give the perception that the air conditioner is not working. To avoid this, replace swamp cooler window units with central air conditioning units or with window units that do not use the swamp cooler technology.

Other Considerations

• The problem could be outside of the air conditioner itself. A poorly sealed home, ineffective insulation, roof leaks, improper dryer ventilation and many other problems can contribute to high relative humidity indoors. It could be that humidity levels are high enough to compromise the effectiveness of your air conditioner. Treat high indoor relative humidity with weather-stripping, good insulation, proper ventilation and electric dehumidifers.