Exhaust fans are used to carry unwanted air from various parts of the house to areas where it can be safely released. Many exhaust fans are installed while the house is being constructed, but if you are doing remodeling work that necessitates the creation of a new exhaust fan, be very careful how you insulate around it. Insulation should never be installed over any part of an exhaust fan.
In residences, exhaust fans are typically seen in two primary locations: the kitchen and the bathroom. In the kitchen, the fan removes the smoky, greasy air generated from cooking and channels it away. In bathrooms, the fan takes away the moist air and moves it away before the moisture can damage the bathroom. In either case, insulation materials should never get in the way of a fan performing its work.
Insulation and Moisture
Insulation, like matting, will stop the fan from successfully drawing up and removing air if it is put over the fan opening or venting. Fans are designed to remove a certain amount of air within a specific time. Insulation drastically lowers that necessary airflow. As a result, moisture and grease pile up in unwanted areas of the home. This causes damage, rot and mildew, and also encourages pests. Always clear away any insulation from exhaust fans so they operate correctly.
Other Insulation Issues
Insulation can cause other problems in addition to reduced airflow. Matting may break apart and pieces might be lost in the fan, which can cause clogs that have to be removed. Too much insulation can also obscure the fan and make it difficult to find in the crawlspace for any additional work.
Exhaust Ports to Outside Air
Your exhaust fans should always vent to outside air, either through one of your walls or through the roof. If insulation is covering your exhaust vent out, then you have an even more serious issue: Your fan is venting into your attic or crawlspace, trapping the moisture. Immediately remodel to move the vent to outside air to avoid serious leaks and mold problems.
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