Roof Replacement and
Roof Repair Specialist(703) 475-2446
July 31, 2011 by - 0 Comments
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The amount of attic ventilation you need to have to prevent ice dams from building up along the edges of your roof is a science. There is a balance between having so much air flow in the upper regions of the house that it affects the climate in the rest of the house and having so little you end up with roof leaks and water damage.
The Manufactured Housing Research Alliance and the U.S. Federal Housing Administration (FHA) have done the research that shows how much ventilation you should have. They have come up with a basic formula you can use to make your own determination.
Start by getting the square footage of your attic space. Do this by multiplying the length of the attic by its width. Now divide this number by 300. The FHA says an attic needs 1 square foot of ventilation for every 300 square feet of attic floor space. So, if your attic is 1200 square feet, you will require 4 square feet of ventilation.
The next step is to determine the minimum square inches needed for the intake and exhaust vents. You do this by multiplying your last number by 144. In the example, it would be 4 x 144 = 576 inches. Keep in mind your exhaust area should not be larger than your intake area.
Now you can go ahead and find a combination of roof vents that total this many square inches. Your roofer can look at your attic and provide guidance for the vent types of attic ventilation for your home. This will keep the ice off the roof in the winter and keep the attic cool and dry in the summer.
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