Attic Ventilation in MN
Attic ventilation is very important. In the summer it will cool down the attic space, making it easier to keep the house comfortable with minimal usage of an air conditioner. The minimum number of both attic vents and soffit vents is the square footage of the attic floor divided by 150. A 2000 sq ft attic should have at least 13 attic vents and 13 soffit vents. If the shingles are white that should be adequate for summer cooling. If the shingles are a dark color I would recommend more.
Ventilation in the Wintertime
It is also necessary to ventilate the attic for winter conditions. If the air in the attic warms up above freezing, any snow sitting on the roof will start to melt, run down to the overhang where it’s below 32 degrees, and refreeze. This condition will cause ice dams and icicles.
If there are enough attic vents, ventilation chutes and soffit vents, it will keep the air in the attic below freezing and the snow won’t melt and therefore no ice dam can form. Ventilation chutes allow the air that comes in the soffit vents to pass unobstructed up into the attic. There should be a chute every 4 or 5 rafters. When in doubt, add more.
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