Bathroom/Laundry Vent to Soffit Vent

Got a newbie question for you. Is it ok to vent bathroom and laundry exhaust to soffit vents?

If I could please get references for or against whichever the case might be.

Thank you.
Joe Myers

Absolutely not. Reference? Common sense. Think about it. Soffit are air intakes.

Well said …

M1507.2 states they must be vented directly to the outside. Some municipalities allowed it but most stopped the practice in 1994.

I call it out on new construction that is Focus on Energy certified. The do it all the time and it is not right, especially when that vent is on vented soffit.

Should always vent to the exterior, venting to the soffits can allow large amounts of moisture to damage the sheathing and cause mold in the attic. I see this a lot on newer and flipped homes.

2009 International Residential Code Part V – Mechanical Chapter 15 Exhaust Systems Mechanical Ventilation. M1507.2 Recirculation of air.
Exhaust air from bathrooms and toilet rooms shall not be recirculated within a residence or to another dwelling unit and shall be exhausted directly to the outdoors. Exhaust air from bathrooms and toilet rooms shall not discharge into an attic, crawl space or other areas inside the building.

Maybe I should have written this so it was a little clearer. Vent hood mounts to underside of soffit. Whether it would be a bathroom or laundry exhaust, is it allowed? Whether for or against, please provide code reference.

Keep in mind you’re not a code compliance inspector. Even if duct termination at a vented soffit is allowed in your jurisdiction, it’s still a terrible idea and you have every right to say so. The client is paying you for your professional opinion.

I don’t know what you mean by a “vent hood” - vent hoods are typically installed over cooktops. If you mean an exhaust vent termination through a soffit, then yes, they are OK because they vent fully to the exterior. Simply stuffing and open exhaust duct into a soffit and hoping the moisture finds its way out through the intake perforations in the soffit is NOT OK.

Bathroom exhaust vents installed on a vented soffit could add moisture to the attic. The warm moist air enters through the soffit and can freeze on the sheathing/lumber in the winter and may help feed mold growth in warm months. Consider a roof vent.

Thank you Chuck. I believe you answered the question correctly and a little more clearly than I did.

The local AHJ quoted the same code which Brian referenced however my interpretation was into those area’s, where I am going through the soffit to the exterior.

Thank you everyone for the responses.