Home comfort in the summer may depend upon both an A/C and dehumidifier. Technically, they can be one and the same: The first air conditioner was principally designed to dehumidify the work space inside a large factory. That’s why it was called an air conditioner — not an air cooler. Decreased humidity and cooling effectiveness are linked. Moist air holds heat more efficiently so it feels hotter, while dry air feels cooler. Therefore, humidity reduction is an important ancillary function of any air conditioner. Consider how an A/C unit also dries your interior air as a side effect of cooling it.
The blower fan in the air handler draws warm interior air through an evaporator coil circulating frigid refrigerant vapor. As the air contacts the chilled coil, heat is extracted and the air is cooled. In addition, water vapor instantly condenses out of the air the same way it drips from the side of a cold drink on a hot, humid day. The amount of condensate removed from the air by a central A/C can exceed many gallons on a humid summer day along Florida’s Gulf coast.
Carrying the load
The cooling load of a house is the amount of BTUs of heat that must be removed from the air to maintain a comfortable target temperature of around 75 degrees. However, cooling load calculations are divided into two figures: sensible cooling load and latent cooling load. Sensible cooling load refers to the amount of heat energy that must be extracted to keep the temperature within limits. Latent cooling load is a figure that expresses the capacity of the air conditioner required to dehumidify a home to a particular relative humidity. Latent cooling load is also related to the overall airtightness of the house. Homes with more air leakage experience greater infiltration of humid outdoor air and therefore put an extra load on the A/C unit.
It’s the humidity
In many climates, the standard humidity extraction process of a central air conditioner is sufficient to keep indoor relative humidity below 45 percent, the maximum for optimum cool comfort. However, homeowners in Sarasota and the vicinity experience particularly high outdoor humidity levels, normally ranging between 50 percent to 93 percent during a typical year and rarely dropping below 35 percent. These heavy latent cooling loads frequently push the humidity extraction function of a central air conditioner beyond its capacity to maintain indoor levels in the comfort zone.
The combination approach
In humid climates like Sarasota and Bradenton, the best comfort results may come from utilizing both an A/C and dehumidifier in combination. Most residential dehumidifiers operate on the same basic principle as an air conditioner. Warm interior air drawn over coils circulating cold refrigerant causes water vapor to condense out of the air. Both the A/C and dehumidifier extract humidity. However, unlike an air conditioner, a dehumidifier has no cooling function. Humidity extraction is the only function the unit is engineered to perform and a dehumidifier therefore removes a greater percentage of water vapor from the air than an A/C unit alone.
A whole-house solution
The most effective dehumidifiers are whole-house units that draw air directly from your cooling and heating ductwork. Because all the air in your home circulates through the ducts multiple times every day, these units treat the home’s entire air volume rather than just a single, enclosed space like a portable dehumidifier. Air diverted from the main duct into a bypass loop passes through an evaporator coil and is dehumidified. The dry air is then looped back into the duct, cooled by the A/C and circulated throughout your house. In this way, effective dehumidification is accomplished without any restriction of system airflow in the ducts. Unlike portable, single-room dehumidifiers, whole-house units are plumbed directly to the household drain system so no user maintenance such as draining condensate pans is required.
Proudly serving Saratoga and Manatee counties, Aqua Plumbing & Air has delivered quality service to local homeowners since 1974. Ask us about the benefits of utilizing both A/C and dehumidifier units to keep your interior environment cool, comfortable and healthy.
Written by John Miller