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When the time has come to install a gable attic fan, the first consideration will be to obtain a fan that will move the particular volume of air at a rate that is sufficient to ventilate the attic.
This can be done by establishing a fan rating that is based on the Cubic Feet Per Minute, or CFM of air that a fan will move. If a fan is too small for the cubic feet of area, it will not be able to move the volume of air, no matter how long it is left to run. Knowing this, one might think that installing a huge fan will eliminate the need for any calculations.
However, the question still remains with regard to how big a fan would have to be in order to be considered huge. In addition, large fans are quite expensive to purchase and install, and in some instances a large fan may require an additional electrical circuit. In light of this information, a cost conscious homeowner would be wise to take a few minutes for some basic three-way calculations.
The dimensions required to determine the CFM are the height, width, and length of the attic, along with the configuration of the roof. If the roof is peaked, this will add more volume than in a building where the roof is flat. Finally, these dimensions are not considered critical, or in some way need to be noted in feet plus inches. Rounding any dimension up to the nearest foot will be adequate for these purposes.
There are a number of fan calculation tables on line and all that is necessary in order to establish the correct CFM is to enter the dimensions of the attic. With this calculated solution in hand, one can begin to shop for a fan, compare costs and consider the installation.
Filed under: Gable Fan Guides
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