Desiccant Dehumidifiers

A desiccant dehumidifier currently under development could be what the nation’s comfort-seeking homeowners want as they address their indoor air-quality issues.

The DD 400-G hangs out of the way in the basement, comfort-ably warding-off air-borne critters that thrive on humidity.

Today’s houses are built to be virtually air-tight, so those portable plug-in units where you empty the pan are no longer adequate. The DD 400-G, manufactured by NovelAire Technologies of Baton Rouge, La., ties directly into the central HVAC system. Reducing a home’s humidity keeps dust mites, mold, mildew, bacteria and viruses at bay.

Large propane- and natural gas-fired desiccant dehumidifiers have been used for years in the grocery industry and other commercial applications; the DD 400-G is the first model targeted at the homeowner/small-business market.

The desiccant dehumidifiers being tested are small enough to be integrated with HVAC systems already in homes.

“It’s a fairly small unit, so it can be integrated with HVAC systems,” reports Gregory Kerr, director of research and development for the Propane Education and Research Council. The Propane Education & Research Council recently awarded a $125,000 grant to the Texas Railroad Commission to study the cost-effectiveness and engineering capabilities of the device.

“It’s a good technology and one that’s been around a long time, but it hasn’t been applied to smaller units before,” observes Steve Jeager, AFRED’s assistant director of technical services.

“The big challenge has been to make these more efficient and affordable for the homeowner,” adds Ralph Terrell, manager of technical development for TECO Energy, a utility provider in Florida also taking part in the project.

“To put them in a home they have to be made more fuel-efficient,” Terrell says. “It’s going to be marketed both as a product to make your house healthier and for comfort.”

The propane industry estimates a potential annual annual gas load of 200 to 300 gallons per residence – about the same as a standard hot water heater.

Perhaps best of all, a dehumidifier gets its biggest workout during the warm and damp weather conditions of propane’s traditional off-season.

A change in home construction standards should help build a residential marketplace. Within a decade, tougher indoor air-quality requirements from the American Society of Heating, Refrigerating and Air Conditioning Engineers will become the national standard for new-home construction.

“It will require that new air be introduced to the home,” explains Dan Kelly, director of the Texas Railroad Commission‘s Alternative Fuels Research and Education Division. Under the standards, humidity in the outside air that is introduced into the home will have to be driven out.

“It’s going to be a new market for our industry with new construction, and we believe there will be a market for retrofits as well,” says Kelly.

The propane marketplace as a whole could gain an extra 100 million gallons per year.

In addition to a cleaner and more comfortable environment, homes equipped with the units can save money on electrical cooling costs.

“Half of the energy that goes into an air conditioner is to take moisture out of the air,” explains Kerr. “People will be able to set their air conditioners higher because the air is less humid. This is something that folks in the Southeast should definitely pay attention to.”

Unit testing is underway in homes throughout the Gulf Coast region, with results and analysis due by year’s end.

Biggest new market

“The biggest new market here in years is indoor air-quality,” says Jeager. “We can service the whole house – and it uses propane, which is a pretty good deal if you’re a propane marketer.”

The old plug-in units on the market are all wet when compared to desiccant technology, project supporters believe.

“They aren’t as efficient, and they are not a whole-house dehumidifier,” Terrell points out.

A desiccant dehumidifier utilizes silica – the same material in those “do not eat” keep-dry packets found inside the packaging of electronic equipment.

Inside the DD 400-G is a rotating silica wheel. Air from the room is drawn through the wheel and the desiccant absorbs the moisture. As the dry air is returned to the room, a gas burner causes the desiccant to release the moisture into the air stream that is exhausted outside. The result is a relative humidity of about 50 percent.

According to Terrell, a room at 76 degrees Fahrenheit and 50 percent relative humidity is just as comfortable as a room at 72 degrees and 60 percent humidity. “For each degree that the thermostat is raised, typical cooling savings are 5 percent to 7 percent,” he says.

Colds, allergies and asthma are reduced as the dehumidifier works because bacteria and germs cannot spread through the air when the humidity is at 50 percent, Terrell says, referencing the upcoming building standards.

Moisture control also is the easiest way to control mold growth. That means the unit can be promoted as a means for residential and commercial landlords to avoid lawsuits over indoor mold issues.

“Mold is gold for many litigation attorneys,” Terrell says. “No one wants the bad publicity that can occur with litigation associated with having a ‘sick’ building.”