How Do I Choose the Best Crawl Space Fan?

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  • Written By: Robert Partain
  • Edited By: A. Joseph
  • Last Modified Date: 30 July 2014
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In order for to choose the best crawl space fan, you will need to do a bit of work before ordering the appropriate unit. You will need to make a visual inspection of the crawl space, measure the size of the area and determine what crawl space hardware will be needed to complete the job. Crawl space ventilation fans can be used in structures that have block, brick or concrete foundations. It will be important to choose the best unit that is designed for the type of foundation used in the home.

To complete the visual inspection, you will need to get under the house, with a flashlight, and look at the area. If the soil is damp, a moisture barrier of plastic sheeting should be applied as part of your project. Inspect the floor joist above your head to see whether water droplets are present. If they are, you have a severe moisture problem that can lead to rotting of the wood, mold and sagging floors if not corrected.


To choose the best crawl space fan, you will need to make an important calculation called cubic feet per minute (CFM) or cubic meters per minute (CMM). This is a measurement of how much air can flow in a predetermined amount of time. For crawl space fans, the time is 15 minutes, so it will measure how much air is moved during a 15-minute time period. To calculate the CFM or CMM that your crawl space fan will need, use the measurements of the crawl space to determine its cubic volume, then divide by 15. A fan with the correct CFM rating will be able to fill the crawl space with air in 15 minutes, or you might need purchase and install more than one crawl space ventilation fan in order to meet the minimum CFM or CMM rating.

In order the choose the best crawl space fan, you will also need to know what type of crawl space hardware will be needed to complete the job. These units can be either freestanding units or installed units. Freestanding units need no hardware other than an electrical outlet. Installed units should be used when the structure already has vent holes cut into the foundation.


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