Attic Ventilation

• One area where leaking ventilation fans should be of particular concern is in the attic. If you use ventilation fans in the attic -- especially powered attic fans -- they can sometimes pull air-conditioned air up into the attic from the house below. This not only decreases the energy efficiency of your air conditioner by forcing it to work harder to maintain a consistent temperature, it renders the attic fans ineffective in providing for proper ventilation in the attic, which, in turn, can lead to serious problems ranging from ice dams, to wood rot, to mold and mildew growth.
  
  

Other Parts of the Home

• In other parts of the home, a leaking ventilation fan typically doesn't have as severe consequences, but is still deserving of attention. Ventilation fans in bathrooms and kitchens, for example, can sometimes leak cold air in when the fan is not in use. Cold air leaking in through fans lowers the air temperature in the home, forcing your heater to work harder and less efficiently to maintain a consistent warmth inside the home. Warm air leaking from inside the home out through an unused ventilation fan can have the same effect.
  
  

What to Do

• The good news is that a leaking exhaust fan can be easily resolved in a few basic steps. Powered attic ventilation fans should be removed altogether; they tend to cost more in electricity usage than they save homeowners in energy costs. Moreover, attic ventilation is more effectively achieved through the use of soffit vents, rafter vents and installing and maintaining insulation in the attic. For kitchen and bathroom exhaust fans, hardware and home supply stores sell ventilation fan covers that can be easily attached to the fans using magnets to prevent cold air from leaking in when the fan is not in use.
  
  

Other Considerations

• You may be tempted to remove kitchen and ceiling ventilation fans altogether, rather than install vent covers over them, but this is a bad idea. According to the Environmental Protection Agency, "If too little outdoor air enters a home, pollutants can sometimes accumulate to levels that can pose health and comfort problems." Given the relatively low cost of purchasing and installing vent covers or removing attic ventilation fans -- compared to the potentially serious health risks of living in a poorly ventilated house, leaving your ventilation fans in place and preventing air leaks through them is clearly the ideal choice.