It’s likely because you have an indoor fan that is installed at at damp, outdoor location like a screen porch. Because indoor fan blades typically are a composite wood product that will not withstand the changes in humidity on a covered porch, they sag over time. Also, the metal components of an interior-rated fan installed outside will rust prematurely, and the motor will likely freeze-up or short-out, usually before the end of the second summer season. 

   So you need to replace it with a fan approved by UL (Underwriters Laboratories) for outdoor installation. Look for the UL-approval notice on the box and the small UL sticker on the fan itself. The UL certification is called “listed” in the building code and there are two types of listed outdoor fans:

1. “UL Listed for Damp Locations” is the rating you need for a fan that will be installed in a covered outdoor location where rain cannot reach the fan. This rating is also correct for fans installed in a bathroom with a tub or shower, and in small enclosed laundry rooms. 
2. “UL Listed for Wet Locations” is for fans that are installed completely outdoors (in a patio, for example) or close enough to the edge of a roofed area for rain to blow on it occasionally.  If you are replacing ceiling fans as part of a project that requires a building permit and inspections, the inspector will verify that the fans you install are correctly rated for where they are installed. But, even if there is no building inspector looking over your shoulder, getting a fan UL-approved for where you are installing it will save you from premature corrosion and failure later—not to mention, droopy blades.
   

    Also, see our blog post  What is the minimum height of a ceiling fan above the floor?

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Here’s links to a collection of some of our other blog posts about APPLIANCES: 

• What are the code requirements for ceiling fan installation? 

• What is the average life expectancy of a ceiling fan?

• How does a home inspector check the ceiling fans? 

• What is the code requirement for ceiling (paddle) fans near or above a swimming pool? 

• How close can a smoke detector be to a ceiling fan?

• Does a home inspector check ceiling fans?

• Does code require a ceiling fan to be grounded?

    Visit our APPLIANCES page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.