When did the building code begin requiring bathroom vent fans to discharge to the exterior (not the attic or crawl space)?
Thursday, April 4, 2019
Although bathroom vent fans have been an acceptable alternative to a window for the required ventilation of a bathroom for many years, the requirement that it be ducted to the exterior did not come along until 2003 or 2006, depending on how you interpret the International Residential Code (IRC) and the corresponding Residential Edition of the Florida Building Code (FBC) for the two code editions. So a vent fan that terminates in the attic, like in the photo below, is no longer acceptable.
The 2003 edition of the IRC states at M1506.2 that “exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit.” But, is an attic or crawl space considered to be “within the residence”?
That question was resolved in the 2006 IRC edition with M1501.2 stating “the air removed from every mechanical exhaust system shall be discharged to the outdoors. Air shall not be exhausted to the attic, soffit, ridge vent, or crawl space.” So, depending on how the local jurisdiction interpreted the code, termination at the exterior was required beginning with the 2003 or 2006 code edition.
Also, see our blog post Does a half bathroom (no shower or tub) require an exhaust fan?
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