Dehumidification

Dehumidification is the process of removing moisture or humidity from the air. Levels of humidity can greatly affect personal comfort. If would be a real oddity to have too low of humidity in the summer. Central Air Conditioning removes humidity from the air which is the prime principle of air conditioning. Cooling the air is simply a by-product of that function. Many people have portable dehumidifiers in their basements to supplement the air conditioning. Air conditioning only dehumidifies when the unit is operating and because the system shuts down based upon temperature and not humidity comfort levels can seldom be reached on moderate or cool summer days when the temperature indoors is not calling for cooling. Air conditioning on a hot summer day should maintain about 50% RH. A dehumidifier in the basement operates based upon humidity, not temperature, and will not lower the temperature of the surrounding space. These units operate quite efficiently and require draining of the storage reservoir. The dehumidifier will automatically shut off before the water level overflows and may require emptying every couple of days in the summer. The solution to this minor problem is to position the dehumidifier over a floor drain and remove the reservoir. A short extension to the drain spud that usually comes with the unit will permit the condensate to go direct to the floor drain and save the homeowner a ton of time and discomfort.

A properly charged and sized air conditioner will provide a 15 to 20 degree temperature drop to the air over a cooling coil. This spread in temperature is sufficient to condense moisture out of the air in the same manner as a chilled glass of pop or beer will condense moisture on the outside of the glass on a hot summer day. Excess humidity can generate mold and create a series of health problems and therefore is best controlled. This is also why it is unwise to oversize a new air conditioner as the excess capacity of the A/C will lower the temperature quickly and cycle off before the humidity level has been reached making the occupants feel cold and damp instead of cool and comfortable.

Wine rooms or cellars are one location where higher humidity levels are required so that corks on bottles do not dry out and spoil the wine. This is why most wine rooms are designed with only a 10 degree temperature drop across the evaporator coil that reduces the amount of condensation that is removed.

Refer to the “Learn About” section for “Humidity” to learn more. Raising the temperature of a space will also lower the relative humidity.