Ask Energenie

September 1998

Table of Contents

1. A musty smell comes out of my air registers whenever I turn my central air conditioner on. What causes this? Is there some kind of freshener I can use to eliminate this odor?
2. I have heard that radon poses health risks only in certain geographical "hot spots." Is this true? If so, where are these "hot spots?"
3. Have you any suggestions for improving the circulation of air through my home from our central air conditioner?
4. What is the greenhouse effect?
5. Do you have any suggestions for improving the performance of my evaporative cooler?
6. Should I abandon my home if I discover high levels of radon?

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1. A musty smell comes out of my air registers whenever I turn my central air conditioner on. What causes this? Is there some kind of freshener I can use to eliminate this odor?

"The source of the odor likely is mold growing on the air conditioner coil or in the drip pan that catches the condensate from the coil," said Doug Walter, president of Kansas Building Science Institute, Manhattan.

Mold growth on the coil is caused by an accumulation of household dust, to the point of partially plugging the coil.

"The plugged section of the coil can absorb condensate from the rest of the coil, but stay warm enough to support mold growth," Walter said.

A plugged condensate drain causes water to stagnate in the drip pan. Check to see if any water is coming out of the condensate drain after the air conditioner has been running for at least five minutes. If not, the drain is probably plugged.

"You might also check for moisture around the base of furnace, which is evidence that the drip pan is overflowing and the condensate is running down through your furnace," Walter said.

A dirty coil often can cause a plugged drip pan as "mud" drips into the pan with the condensate.

Neither problem can be solved by spraying an air freshener into the return air ducts.

"You will need to have a service technician come and clean the coil, drip pan and condensate drain," he said. "This may require cutting an access door into the sheet metal plenum which houses the air conditioner coil."

The service technician can clean and disinfect the coil by using a commercial solvent.

"It may also be necessary to adjust the slope of the drip pan so it will drain all of the condensate out of the pan after the air conditioner shuts off," Walter said.

Getting rid of the disagreeable odor has other advantages.

"Not only will your air conditioner smell better after the coil has been cleaned, it will also run more efficiently and cool better," Walter said. "And when it comes time to crank up your furnace, you'll get better heating performance, too."

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2. I have heard that radon poses health risks only in certain geographical "hot spots." Is this true? If so, where are these "hot spots?"

This is not true. Test results have indicated high radon levels in homes all across the country.

"It was once thought to be a localized problem associated with high uranium concentrations in former mining sites, but this is a myth," said Bruce Snead, extension specialist in residential energy at Kansas State University.

"However, in the mid-1980s, it became clear that naturally occurring radon posed significant public health risks," Snead said.

State radon surveys have indicated homes with elevated radon levels in all parts of the United States, not just in recognized "hot spots" like the Reading Prong in Pennsylvania, New Jersey and New York.

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3. Have you any suggestions for improving the circulation of air through my home from our central air conditioner?

"Although air distribution within a home ultimately is dependent on proper design and installation of the system, a number of things can impede proper air flow," said Richard B. Hayter, director of Kansas Energy Extension Service at Kansas State University.

First, be sure you have replaced the air filter in your furnace recently. Next, if your furnace fan is belt-driven, be sure the belt tension is correct and the fan is turning at the proper speed. (You may wish to have this done by a service technician.)

The supply air registers that distribute air into the rooms also may be equipped with dampers.

"The position of these dampers is fully open in rooms needing more air and partially closed in those needing less air," Hayter said. "In addition, these registers should not be restricted by furniture, curtains or any loose items such as a child's toy."

Some homes with well-designed air distribution systems are equipped with "balancing dampers." These dampers are in the ductwork leading to supply air registers.

"Such dampers usually will have an external handle showing the position of the enclosed damper," Hayter said.

"Adjustment of these dampers may help in improving the distribution of air within your home. However, completely closing these dampers will restrict air flow and reduce furnace fan performance," he said.

Proper air flow also relies on proper return of air to the furnace. Return air grills should be located throughout the home to minimize any restrictions of the return air. Often, these grills have been blocked by furniture or other obstructions and should be checked to make sure there is no interference.

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4. What is the greenhouse effect?

The "greenhouse effect" is thought to be one of the reasons for the gradual warming of our planet.

"An increase in concentration of certain atmospheric gases tends to trap or absorb the infrared radiation which normally would have partially radiated to outer space," said Richard B. Hayter, director of Kansas Energy Extension Service at Kansas State University.

"In trapping the heat, these gases act much like the glass over a greenhouse, thus the greenhouse effect," Hayter said.

The gases which tend to trap the heat represent an extremely small portion of the total gases in our atmosphere.

"Greenhouse or trace gases that absorb infrared radiation include carbon dioxide, methane, nitrous oxide and chlorofluorocarbons such as the chemicals once used in the manufacture of foams and as refrigerants in air conditioning and refrigeration equipment," Hayter said.

Because the total volume of these trace gases is small, their concentration can be easily changed.

"A major contributor to this increased concentration in trace gases is fossil fuel combustion of coal, oil and natural gas which produces carbon dioxide at a faster rate than can be absorbed by plants," Hayter said. "This is becoming particularly true as we reduce our forest acreage."

Energy conservation is part of the solution to slowing the greenhouse effect.

"By more efficiently using both electricity and fossil fuels such as oil and natural gas, we can reduce the amount of carbon dioxide emitted into the atmosphere," he said. "Energy conservation already makes economic sense and the environmental benefits are becoming more evident."

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5. Do you have any suggestions for improving the performance of my evaporative cooler?

"An evaporative cooler is a device that reduces the dry-bulb, or air, temperature by evaporating water in the air stream," said Richard B. Hayter, director of Engineering Extension at Kansas State University.

Hot outdoor air is cooled by the evaporation of water which flows through pads surrounding the evaporative cooler. This "cool" air is then transferred to your home at a lower temperature than the outdoor air but at a much higher humidity.

"Your evaporative cooler needs regular, routine maintenance to assure it will perform properly," Hayter said.

Maintenance includes regularly replacing or cleaning the pads to insure uniform water flow and sufficient surface area for maximum evaporation. Also, inspect the small tubing that distributes water through the pads, making sure that water flow is uniform from the tubing or troughs to the pads and across the entire pad surface. The belt between the motor and fan should have proper tension and operate the fan at the proper speed. The sump in the base of the evaporative cooler should be cleaned to avoid clogging the pump with debris or sediment.

"Because the evaporative cooler introduces a great volume of outdoor air into the home, it is necessary to have unrestricted paths to discharge the air from your home," Hayter said. "This involves opening windows on the opposite side of your home from your evaporative cooler."

Closed windows create insufficient exhaust, restricting air flow because of the increased pressure in your home.

"Evaporative coolers provide an economical way to cool homes in locations within the state with relatively low humidities," Hayter said. "Typically, evaporative coolers cannot give satisfactory results where humidities are high because they create excess humidity in your home."

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6. Should I abandon my home if I discover high levels of radon?

Absolutely not.

"Radon levels can and have been consistently reduced in virtually all types of homes to below the EPA guideline level of four picocuries per liter," said Bruce Snead, extension specialist in residential energy at Kansas State University.

The costs of work to reduce radon levels in your home will range from several hundred to a few thousand dollars. A qualified contractor can typically complete the work in a day or two.

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Ask Energenie is produced by the Kansas Energy Extension Service through Kansas State University. This material was prepared with the support of the U.S. Department of Energy (DOE) Grant No. DE-FG47-92-CE60210. However, any opinions, findings, conclusions, or recommendations expressed herein are those of the author(s) and do not necessarily reflect the view of DOE.