Achieving Balanced Humidity

August 4, 2004
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The Dave Lennox Signature Collection SignatureStat™.
How can humidity be controlled to maximize comfort in homes and businesses? Is there a way to reach a common ground and provide indoor comfort levels that will satisfy both contractors and their customers? Too little humidity can create health concerns, discomfort, and skin irritation; too much humidity can result in mold growth.

The News put questions to HVAC equipment manufacturers, asking them what each was doing to find the right mix necessary to achieve the most satisfactory results.

"There's no single piece of equipment that meets all of these [health and mold] requirements," said Craig Ellis, director of sales for Fedders Corp., Liberty Corner, N.J.

"Historically, people have always sold humidifiers to increase the humidity in cold-weather climates. Now we're seeing dehumidification systems in regions where there's excessive humidity. A variety of equipment is used to treat all aspects of IAQ - which includes air cleaning, humidification, dehumidification, and ventilation."

Rick Stoltz, marketing communications director for Skuttle Indoor Air Quality Products, Marietta, Ohio, pointed out the seasonality of humidification problems.

"Household mold is often a summertime concern associated with naturally warm, moist air that remains unchecked by air conditioning or mechanical dehumidification," Stoltz explained.

"Year-round culprits can include inadequate ventilation, the influx of ground water, and/or plumbing leaks. On the other hand, dangers commonly associated with dry indoor air - viruses, respiratory ailments, ozone production, static electricity, damage to woodwork, etc. - are primarily fall and winter concerns, the seasons for humidification."

One manufacturer wanted to clear the air about what HVAC equipment can or cannot do to control humidity. "Homeowners have been led to believe that air conditioners control humidity," said Ty Foren, director of marketing for Therma-Stor LLC, Madison, Wis.

"This simply is not true. Homeowners exacerbate humidity problems by overcooling surfaces below the outdoor dewpoint, thereby creating cold surfaces and condensation in their home; and running the blower continuously during the air conditioning season, causing re-evaporation and increased infiltration of humid air.

"A conventional air conditioning system is not designed to control humidity below 50 percent on a continuous basis. Nor can an air conditioner humidify. New, high-efficiency air conditioners struggle to control humidity while also providing high energy efficiency," he said.

"An air conditioner does some dehumidification as a byproduct of cooling. However, this byproduct only occurs when the air conditioner is running," Foren said.

"Contrast this with a dehumidifier, which senses the indoor relative humidity (rh) and runs only when necessary. When heating, it may be necessary to add humidity to maintain adequate relative humidity for comfort."

The Vehere pool and spa humidity controller.

Taking Action

Adam Stark, senior product manager, IAQ and controls, for Lennox International, Richardson, Texas, said his company is "hitting and dealing with rh and other IAQ issues head-on in a multiprong approach."

Stark said past problems of getting accurate readings, short of performing a whole-house audit, are being addressed with a simple monitoring device. "We have teamed up with AirAdvice," a Portland, Ore., manufacturer and third-party testing company, "aiding in our ability to monitor, diagnose, and offer solutions based not on best guess, but true, hard facts.

"With the participation of the independent Lennox dealer, a monitor is placed within a consumer's home. Once plugged into a standard 110-V outlet and a phone line, the unit takes 1,440 samples per day and downloads the consumer's particulate (dust, dirt, pollen), bioaerosols (bacteria, viruses), VOCs (odors and chemical vapors), temperature, rh, carbon dioxide, and carbon monoxide levels in the middle of the night to the AirAdvice secured Web site, ready for the dealer to further download and provide the consumer with a detailed report outlining the possible issues or lack of them.

"The key advantage is that all recommendations are based on core facts and help the consumer understand what the issues are, relationship to their concerns, and how the dealer can solve them correctly the first time."

Other manufacturers also believe further steps need to be taken to control rh.

"Experts agree that the safest, healthiest indoor rh range is between 30 and 60 percent," said Stoltz. "Skuttle and other residential humidifier manufacturers recommend a humidistat setting between 35 and 45 percent because many homes have inadequate insulation and vapor barriers to prohibit the buildup of condensation at rh levels above 50 percent.

Dehumidification options available from Therma-Stor include the Ultra-Aire ADP 135H high-efficiency dehumidifier.
"Most humidistats today (including Skuttle's) are designed not to exceed approximately 45-percent relative humidity - well below the level at which mold proliferates."

"It's recommended that the humidity level in a home remain between 30 and 50 percent to keep it from feeling too dry or too humid, reducing the ability for mold to grow and dust mites to thrive," said Tom Overs, Lennox Industries product marketing manager for Indoor Air Quality. "Dust mites and mold can trigger allergies and asthma in some people. Proper humidity levels can reduce the potential for mold growth.

"Often, homeowners do not realize condensation on their windows can be caused by high humidity compared to the outdoor temperature," he said. "Appropriate control of humidity by comparing indoor humidity and outdoor temperature can reduce the potential for condensation on windows."

The Dave Lennox Signature Collection SignatureStatâ„¢, Stark said, handles humidity "not just by humidifying or overcooling, but by having the capabilities to regulate the fan blower motor, compressor speeds, and humidifier for maximum humidity control and comfort.

"In combination with a variable-speed blower motor and multistage outside unit, the SignatureStat can remove up 75 gallons of water by day compared to our best competitor at 25 gallons," he said. "Therefore, we not only have a full understanding of relative humidity, its relationship to comfort and health issues, but how best to make sure it is kept in line."

According to Ellis, "Fedders provides an accurate humidistat with each product, along with recommendations for setting proper indoor humidity levels based on the outdoor temperature."

Foren offered solutions, including air conditioning with reheat. "An A/C unit can be doctored to do more dehumidification, but the only way an A/C unit can always keep a home below 50 percent is with reheat - very energy intensive, and costly to the home or building owner - yet the average homeowner will shriek when they receive their first reheat utility bill.

"Dehumidification keeps it dry for health and comfort. The most practical way to ensure humidity control is with supplemental dehumidification from a high-capacity, high-efficiency, ventilating dehumidifier.

"Dehumidifiers that deliver high capacity in terms of water removal, high efficiency in terms of lower energy consumption, and the ability to operate in cold basements and crawlspaces, plus offering fresh air ventilation, are not available at local mass retail outlets."

Foren added that Therma-Stor LLC designs, manufactures, and distributes ultra-efficient dehumidifiers under the brand names of Santa Fe, Santa Fe HC, Santa Fe Rx, Ultra-Aire APD, and Vehere.

Ultimately, he said, "Mother Nature is boss. The dewpoint of outdoor air is the boss given whatever is outside seeking to get inside. Each 100 cfm of outdoor air (70 degree F dewpoint) requires the removal of 10 gallons of water per day. Appliance-grade dehumidifiers sold at retail only remove pints per day of water, not the gallons per day required for health and comfort."

Publication date: 08/09/2004

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