Condensation Problems with House Heaters

Indoor Condensation

• Condensation occurs when warm indoor air comes into physical contact with a much colder surface. For this reason, single-paned windows, glass doors or uninsulated walls are more likely to house condensation than are other areas of the home, because these areas are literally gateways between cold air outside and warm air inside. In addition to the condensation itself, you may notice discoloration on windows and walls that have condensation, as well as mold and mildew growth. These are the parts of the home that you are most likely to find condensation, but condensation anywhere in the home indicates that indoor moisture levels have become problematic.

Heating and Condensation

• Controlling indoor moisture and condensation begins with identifying the source of the excess moisture. Under normal circumstances, the large amounts of moisture created by whole-house heaters is expelled through ventilation fans and exhaust vents. Should these vents or fans become blocked by birds' nests, leaf piles or other debris, the moisture cycles back into the home. In these cases, condensation won't necessarily be localized at the heater; the house heater simply adds to the home's overall moisture levels and it is not until that moisture reaches a colder surface that it turns into condensation. A house heater could therefore easily be the cause of the indoor condensation you observe.

Addressing the Problem

• The first step to addressing this problem is to remove any built-up debris around the exhaust fans and ventilation ducts that your heater uses. If your home uses a chimney, clear similar debris from the chimney flue and check for corrosion at the junction between the heater and the flue. Repair any corrosion or breakage on the chimney flue right away, and have a repair professional check the flue and chimney to make sure it is tightly sealed to prevent heater exhaust from cycling back into the home. Check the area in which you originally found the condensation to see if it goes away after using the heater again.

Other Considerations

• Proper ventilation is the first line of defense against indoor moisture, regardless of the cause of the moisture. Use exhaust fans in the kitchen and bathroom and install inexpensive exhaust fan covers to prevent air from leaking in or out of the home when the fans are not in use. Keep the attic and basement well-ventilated through soffit vents, rafter vents and proper insulation, as these parts of the home are much more likely to experience moisture problems than other areas.