How to Ventilate an Attic

The benefits of proper attic ventilation are twofold: the reduction of heat build up cools the house and reduces energy cost. There is also the reduction in moisture vapors lessens the likelihood of insulation and building material deterioration. Your options include natural, wind assisted and power techniques to ventilate an attic and even more methods to accomplish these. Bottom line: the more air flow in from outside to the lower part of the attic roof, the better.

Determine the Proper Attic Ventilation

  1. Measure the dimensions of the attic.

  2. Calculate the ratio of one square foot of ventilation for every 300 square feet of attic space to get the square footage of ventilation needed for the attic. Wet climates may need more and a house with a hip roof may need less. Confirm the standard with local building code requirements.

  3. Decide the type of attic ventilation works best for the attic. Choices range from natural, wind aided, and power aided vents to fans. The more powerful the system, the cooler the attic.

  4. Consider many factors in the decision such as the climate region, shape of roof, roofing material and architectural style.

Attic Vents

  1. Choose from soffit vents, eave vents, roof line vents, gable vents, circular vent, exhaust vent, power ventilators, continuous ridge vents and custom and site built vents.

  2. Lay out and measure the location of the vent between the attic rafters, then cut the hole with a saw. Some wall materials may need to be cut with a utility knife.

  3. Level then screw the attic vents to the soffit, covering the hole. Remember, work on the roof in calm, dry weather. Keep the ground area clear in case something falls off of the roof.

Attic Fans

  1. Select a location for the fan on the southern side of the roof since attic fans work best in full sunlight. Center placement of the fan between the rafters to ensure clearance on the underneath side.

  2. Use a saw to cut a hole for the size of the fan through the roofing material.

  3. Place the fan into the hole from lower side of the roof. The upper portion of the flashing should be under the roofing material. The lower portion of the flashing should be in top.

  4. Fasten the fan to the roof similar to the way the flashing is affixed according to the type of roof material.

  5. Reinstall any pieces of the roofing material to cover the sides of the flashing that may have been removed during the fan installation.


  • Be aware of footing on the roof. It's best to wear rubber soled shoes. Take notice of slippery or loose shingles or rotten decking. Avoid power lines and TV antennas.
  • Don't install the fan under overhanging trees or other shady structures.
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