Attic Ventilation Overview 
 
For Electric & Natural Gas Customers

It may seem odd to add insulation for warmth then purposely allow cold air to enter the attic through vents, but this combination is the key to a durable and energy-efficient home. Natural attic ventilation in the winter allows the flow of outdoor air into the attic, reducing the potential for ice damming. Ice damming is a result of snow that melts off the roof from a warm attic and refreezes when it reaches the overhang of the roof next to the gutters. Refreezing at the gutters causes the water to push up under the shingles creating an ice dam that can damage the roof. Proper insulation and venting in the attic keeps the attic cold in winter by blocking the entry of heat and moist air from the ceiling below. In the summer, natural air flow in a well-vented attic moves super-heated air out of the attic, protecting roof shingles and removing moisture while the insulation resists the heat transfer into the house.

Attic/Gable/Roof - Power Vent
An attic power vent, also called an attic or gable fan, usually has a thermostat to monitor the heat in the attic. A predetermined temperature on the thermostat turns on the fan when the set point is reached. The fan will turn on and pull cool air into the attic space until the temperature in the attic drops down to the cooler predetermined set point. The set point temperature to turn on the fan differs depending on climate, however the optimal setting is usually between 100 to 110 degrees Fahrenheit. This attic fan will begin to run when the temperature in the attic exceeds the set temperature and will shut off after the temperature dips below the set temperature. In extremely hot climates, attic fans should be set to higher temperatures to prevent them from running continuously. In colder climates, the opposite is true; once the temperature is below the set point, the fan will not turn on until the set point temperature is reached again. Attic fans, which can be powered by electricity or solar energy, are intended to cool the hot attic space by drawing in cooler outside air either from attic vents or through the soffit and gable.

If your attic has blocked soffit vents and is not well sealed from the rest of the house, attic fans will suck cool conditioned air up through air leaks to the attic. Air pulled into the attic from your living area causes your air conditioner to work harder, which in turn increases your energy usage. The most common mistake homeowners make when installing insulation in the attic is blocking the flow of air at the eaves through the soffit. Never cover the attic soffit vents with insulation - use rafter vents that are secured between the rafters to hold insulation back allowing fresh air into the attic to maintain airflow.

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Related Topics
  • Air sealing
  • Attic blanket
  • Building envelope
  • Cool roof
  • Duct sealing

     

  • Electric heat
  • Energy audit
  • Fireplace damper
  • Furnace
  • R-Rating (attic insulation)
  • Solar attic blanket 
  • Thermostat
  • Windows
  • Video(s)
    The link provided below goes to a web page with a video mainly produced by third parties to educate a public audience.

    attic ventilation, power vent fan, attic power vent, attic fan, gable fan, attic soffit vent
     
     
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