Question

What is the best way to get my existing roof to "breathe" more?

Asked by Frank Lee
Phoenix, AZ

I have a cookie-cutter home here in Phoenix with an asphalt roof, and I need my attic to breathe. I would like a list so I can prioritize. If I could only do one thing, what should I choose? Solar attic fan, roof vents, etc.?

Answer

Review your existing roof venting.

  • Do you have adequate soffit and roof vents?
  • For a balanced system, you are required to have 50% of venting at the soffit and 50% at the highest point of the roof.

Venting calculations

To calculate the required amount of vent, use the following equations.

  • 150 square inches of ventilation per square foot of attic for a balanced system.
  • 350 square inches of ventilation per square foot of attic for a non-balanced system.

Soffit venting

The best type of soffit venting to install is a continuous soffit vent system. Make sure also that all spaces between the joists and rafters allow for a minimum of 1.5 inches of clear ventilation from soffit to ridge.

Ridge venting

Also, at the highest point on the roof, I would recommend the installation of a quality continuous ridge vent.

  • Do not install a combination of venting.
  • For example, do not install ridge vents if you have gable vents or roof "can" vents lower than the ridge.

This will not allow the soffit vents to function and will defeat their purpose.

 

For more information:

Read Danny Kelly's Q&A "How effective are the different attic ventilation methods? I read mixed reviews, and many have a commercial bias."

Tagged In: attic ventilation

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