Controlling humidity in a home is a fine balance: Too much humidity can result in mold growth and a sticky feeling for occupants, while not enough humidity can result in residents experiencing dry noses, throats, lips, and skin. Finding the right level of humidity control to keep homes healthy and customers comfortable can be tricky, but an array of dehumidifier and humidifier options can make that task easier.


Controlling moisture is extremely important as far as IAQ is concerned, because high levels of moisture can result in mold growth, which then can lead to health problems. Molds produce allergens, irritants, and in some cases, potentially toxic substances (mycotoxins), according to the Environmental Protection Agency. Inhaling or touching mold may cause allergic reactions in sensitive individuals, and mold exposure can irritate the eyes, skin, nose, throat, and lungs of both mold-allergic and nonallergic people.

Dehumidifiers reduce high levels of moisture, which can result in mold growth and subsequent health problems. (Photo courtesy of Ultra-Aire.)

An air conditioner can help remove some humidity from a space, but a dehumidifier is often necessary to work in concert with the system in order to remove moisture without overcooling a space. “By controlling relative humidity below 50 percent, you virtually eliminate the possibility of mold growth. Additionally, the enhanced filtration offered by some dehumidifiers contributes to reducing allergic reactions by removing airborne particulate including mold spores and other microscopic debris,” said Joe Hlavacek, business development manager, Ultra-Aire (

Ultra-Aire offers a complete line of energy-efficient, whole-house, ventilating dehumidifiers. The company’s smallest unit removes 65 pints per day (designed for areas up to 1,600 square feet), while the larger units have anywhere from a 90- to a 150-pint capacity (suited for homes as large as 3,500 square feet). In addition to providing dehumidification, Ultra-Aire units feature ventilation control capabilities, which allow homes to breathe properly by providing fresh outdoor air while diluting indoor odors, volatile organic compounds, and stale air. Each unit also includes high-efficiency filtration that effectively removes particulates, while simultaneously keeping the unit’s components clean, allowing it to maintain high levels of moisture removal and energy efficiency.

While dehumidifiers are definitely beneficial for homeowners, they also provide a profitable opportunity for contractors. “Whole-house dehumidifiers aren’t under the same commoditized pricing pressures as other products that contractors offer,” said Hlavacek. “Only a relative handful of contractors understand and promote the benefits of whole-house ventilating dehumidifiers, which allow contractors to sell on benefits and value versus price. In addition, contractors will create more satisfied customers, as they are offering a true solution to excess humidity and ventilation issues. This not only increases the possibility of a positive referral but also helps build contractors’ positive reputations in their marketplace.”

Dehumidifiers can usually be installed in new as well as retrofit applications, provided there is space for the unit, and installation is usually quick and easy, noted Hlavacek.


While maintaining indoor rh at a level that inhibits mold growth is important, a certain level of humidity is also necessary for healthier air and a more comfortable environment. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) states that controlling indoor humidity levels between 40 and 60 percent fosters healthy indoor living while preventing mold growth.

To reach that optimum balance of rh, a whole-house humidifier is often required. Whole-house humidifiers connect directly to the furnace and work with the heating and cooling system to distribute moisture throughout the home. There are many different types of humidifiers offered, noted Tim Barton, vice president of sales and marketing, General Filters Inc. (, including the following:

• Bypass flow-through humidifiers mount on the return or supply duct and connect to a bypass off a supply or return airflow in order to create pressure that drives the air through the humidifying pad.

• Fan-powered flow-through humidifiers mount on the supply plenum and feature a built-in fan that draws the air into the humidifier and across the pad. These are easier to install than bypass flow-through humidifiers since no bypass ductwork is required.

• Steam humidifiers use electrode technology to boil water in a renewable generating cylinder and then inject the pure sterile steam into the duct airstream. A key advantage of this type of technology is the capability to deliver greater capacity outputs to meet challenging humidity loads independently from the warm-air furnace, as a call for heat from the furnace is not required to meet designed rh set points.

Humidifier operation can be made more convenient with a temperature-compensating humidistat, such as the GFX3 offered by General Filters Inc. “This provides an automatic feature where outdoor temperature is measured by way of an outdoor sensor and automatically adjusts the indoor relative humidity to prevent condensation on outside wall surfaces,” said Barton. “The automatic temperature-compensating humidistat has a large-screen digital display that can be wall or duct mounted and is designed for easy operation.”

Skuttle IAQ Products ( also offers a wide range of residential humidifiers, said the company’s vice-president, John Duke Riley, including steam, flow-through, drum, and even spray units. “Our units can be used in both residential new construction and retrofit applications. In some situations where ductwork is not present, we have a steam unit with a blower cabinet that can provide humidified air to an occupied space.”

Installation is simple, said Riley, as Skuttle includes components in the carton that help the contractor complete the installation without going back to the truck, much less back to the distributor.

All humidifiers, regardless of style, require regular maintenance in order to keep operating properly. According to Barton, flow-through humidifiers require the vapor pad to be replaced every heating season, along with the orifice cleaned or replaced, and the strainer cleaned or replaced. Drum-type humidifiers require the drum sleeve to be replaced every heating season, as well as the float valve inspected for operation and cleaning of the water pan reservoir.

“Electrode-type steam humidifiers require an annual replacement of the steam generating cylinder, which comes complete with new electrodes. There is no cleaning involved, making it easy and convenient for seasonal maintenance checkups,” said Barton. “Electric element steam humidifiers require cleaning of the calcium buildup on the electric elements or replacement and a thorough cleaning of the electric element reservoir annually for efficient operation.”

As with dehumidifiers, whole-house humidifiers provide an additional sales opportunity for contractors. “Profit is not a four-letter word, and it is profitable for an installing contractor to offer an in-duct humidification system, just as it is more profitable to offer enhanced air cleaners, zoning systems, or programmable thermostats,” said Riley. “However, the real winner is the homeowner, who is able to live in an environment with these improvements to the basic residential HVAC system.”

The bottom line is that humidifiers and dehumidifiers contribute to a more healthful environment for the customer and a more profitable opportunity for the contractor, which results in a win-win for everyone involved.

Publication date:05/31/2010