Mabry Brothers Inc. in Fort Myers, Fla., dehumidification sales account for approximately 5 to 8 percent of its total air conditioning business.

Job descriptions are important. They inform a person of their duties and provide a metric to determine daily success. Each piece of HVACR equipment has its own job description delineated in the small print of its spec sheets. It is there that contractors will discover what the product was specifically designed to accomplish. In essence, air conditioning units are primarily designed to address temperature and dehumidifiers designed to address humidity levels. It is when the job descriptions begin to intermingle that homeowners may find themselves in an uncomfortable and less efficient environment. Keeping the temperature and moisture duties separate can help keep customer complaints at bay and bring greater efficiencies for many applications.


In an effort to keep the job duties separate, contractors like Mabry Brothers Inc. in Fort Myers, Fla., and Albermarle Heating & Air Inc. in Charlottesville, Va., are installing dehumidification systems from Therma-Stor LLC on an increasingly regular basis. Accounting for approximately 5-8 percent of Mabry Brothers’ total air conditioning business, the Ultra-Aire product line - from model UA-65 to UA-XT150H - has the ability to provide whole-home dehumidification to practically any application.

“With the well-rounded product line from Therma-Stor, we have not found an installation we have not been able to fulfill as of yet,” said Ron Reis, project manager, Mabry Brothers Inc. “Our usage of these products is growing rapidly as the awareness of the local population grows. We market this product to all of our new construction residential and light commercial construction contractors, especially those that are insulating with foam insulation. We also market this equipment to all of our retail customers, especially those that travel north for the summer months.”

The company uses these products to assist with the amount of fresh air that is required to meet the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 62 requirements and to control the high relative humidity common in Southwest Florida.

“In a residential application, we can attempt to control humidity levels with thermostats that control for both temperature and humidity, but in that case we are running the large air conditioning condensing unit to remove moisture,” explained Reis. “If we install the whole-house dehumidifier, we can accomplish that work with a much smaller compressor that will only draw 6.9 amps (115 volts) even with the largest of the units.”

According to Reis, there have been virtually no customer complaints about installing Ultra Aire whole-home dehumidification prod- ucts. “With the permanent resident, we are able to control their humidity level in the house with the smaller compressor allowing them to be much more comfortable at a little higher temperature and saving them several hundred dollars a year in electric costs,” said Reis.

When it comes whole-house humidity control, Therma-Stor suggests the following concepts for contractors to consider:

• Strive to maintain the inside temperature above the outside dewpoint to reduce the potential for condensation within the building envelope.

• Avoid running the a/c blower in the “on” position to prevent moisture on the evaporator coil from being returned to the home after a cooling cycle.

• Overcooling with the a/c is an ineffective and inefficient method of attempting to control humidity. It uses a lot of energy and creates cold surfaces that are more prone to condensation. A better approach is to raise the temperature and reduce the relative humidity.

• Ventilation is important to IAQ. Take steps to reduce excess moisture that may be introduced into the home through ventilation.

• The most effective way to ensure consistent humidity control is through a dedicated dehumidification system.

Customers of Albermarle Heating & Air Inc. in Charlottesville, Va., are reporting less overall home maintenance costs due to consistently controlled humidity.


Dehumidification isn’t necessarily strictly for high humidity regions like South Florida. The technicians under Tom Kavounas, president of Albermarle Heating & Air Inc., service a mixed humid climate clientele. As certified indoor environmentalists, the company is involved with many IAQ problems that relate directly to high humidity issues.

“We also quote dehumidification on all of our new jobs,” said Kavounas. “I would say about 20 percent of the new jobs install dehumidification and 80 percent of the problem houses we correct by installing dehumidifiers.”

The contractor not only installs whole-home dehumidification, but he also offers freestanding models to his customers. The freestanding model is installed by setting it in the space to dehumidify, plugging it in, and locating or providing a drain. Once the desired humidity level is set and the machine is turned on, the job is complete.

“A whole-house dehumidification system is a little more complicated,” explained Kavounas. “Fresh air can be ducted to the return side of the dehumidifier which can then be controlled by Therma-Stor humidity controls. The other return can come directly from the house through a ducted return.”

According to Kavounas, both these ducts will require balancing dampers to ensure that the proper CFMs are coming from each space.

“The supply side can then be distributed directly into the house or ducted into the HVAC system,” he said. “This provides filtered, dehumidified fresh air into the house and reduces run time on the air conditioning system.”


Kavounas reported that his customers were surprised by the results of using humidity control in the home. “Many of our customers have never actually experienced actual humidity control,” he said. “Many now have relief from musty odors and enjoy lower energy bills because they are able to set the thermostat three to four degrees higher and still maintain comfort.”

His customers also reported less nail pops, floors that don’t cup, less painting, wood structures that don’t rot or deteriorate as quickly, and overall a lot less maintenance and cost.

“I have used Therma-Stor exclusively because their products are the most energy efficient, durable, and work well with very few problems,” summed up Kavounas. “Our customers have been very satisfied with the results.”

Reis and Kavounas understand their job descriptions as whole-home comfort contractors and keeping installed equipment running to its peak specifications allows both the a/c and the dehumidification systems to perform their best.

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Sidebar: Install Details

“We will normally install the dehumidifier adjacent to the air-handling unit. The majority of our installations are in the attic space and the air handlers are normally in the horizontal position. We will install a separate air intake grille for the dehumidifier, a fresh air intake duct leading to the outside with either a grille in the soffit or a roof jack penetration, and the supply side of the unit will be connected to the return air side of the air handler. We will set up the controller to run the air handler whenever the dehumidifier is running or there is a call for fresh air. In this way, as we disperse the dry air throughout the system, we can reach all areas of the home and if there is an increase in temperature due to the discharge temperature of the dehumidifier, the thermostat will bring on the condensing unit to satisfy the cooling requirements. We have several installations where we have vertical applications, and these cases we will use the UA-100V and install it in the same manner. We use the UA-65H in condominiums where we have a vertical air handler in a closet, in many cases these air handlers are mounted on a stand and there is a louvered door used for the return air. In a case like that we may not be able to introduce any fresh air, but the unit will fit directly under the air handler, and can be installed with a separate air intake if there is a wall adjacent to the unit that communicates with the main area of the living space, or if not it works just as well just using the air handler closet as the return air plenum, and allowing the air handler to run with the dehumidifier, the air handler will disperse the dry air from the dehumidifier throughout the home.”

- Ron Reis, project manager, Mabry Brothers Inc., Fort Myers, Fla.

Publication date: 08/10/2009