Bathroom exhaust fans exhaust the moisture formed from showers and baths.  They are responsible for exhausting relative humidity out of your home.  Some homes do not have bath fans.  Builders relied on opening a window to exhaust the moisture.  This is not a good option in Fall and Winter.  Most homes also have undersized bath fan.  Building codes only required a fan.  Builders usually installed an inexpensive 50 cfm fan.  This fan usually costs $15.00 to $25.00.  Most codes do not require fans to exhaust moisture out of the attic.  Therefore, in many cases, fans exhaust into soffits or attic.  Not having fans exhaust out of attic will cause mold.  Mold in the attic could cause health issues.  The occurrence of mold may scare away a potential homebuyer or reduce the price of the house.  It usually costs thousands of dollars to remediate the mold.  After time, 50 cfm fans become ineffective.  They get overcome with dust buildup.  A proper bathroom fan should have a power of 1.1 cfm per square foot of bathroom.  A dampered roof cap is the best way to exhaust out a bath fan.  You want to get the moisture from the fan out of your attic as soon as possible.  After several years, it is a good idea to replace your fan.

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