# Bathroom Fans through the soffit??



## JCraver

2009 IRC, new construction, single-family.

Contractor wants to run the exhaust from bath fans through the soffit to the outside.  Is a bath fan an *appliance*; and if so, can he use Sec. 1804.2.6?  If he puts a solid soffit at least 4' in either direction from the center of the exh. outlet (screened louver, etc.), would this then be a compliant install?  If so, should the AHJ be concerned with the eave baffle requirements in the IECC?

*R303.3 Bathrooms.*

_(snip)_ *Exception:*  Ventilation air from the space shall be exhausted directly to the outside.

*SECTION M1501 GENERAL*

*M1501.1 Outdoor discharge.* The air removed by every mechanical exhaust system shall be discharged to the outdoors. Air shall not be exhausted into an attic, *soffit,* ridge vent or crawl space.

*Exception:* Whole-house ventilation-type attic fans that discharge into the attic space of dwelling units having private attics shall be permitted.

*SECTION M1507 MECHANICAL VENTILATION*

*M1507.1* General. Where toilet rooms and bathrooms are mechanically ventilated, the ventilation equipment shall be installed in accordance with this section.

*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. *

*M1507.3* Ventilation rate. Ventilation systems shall be designed to have the capacity to exhaust the minimum air flow rate determined in accordance with Table M1507.3.

*M1801.1 Venting required.* Fuel-burning appliances shall be vented to the outdoors in accordance with their listing and label and manufacturer's installation instructions except appliances listed and labeled for unvented use. Venting systems shall consist of approved chimneys or vents, or venting assemblies that are integral parts of labeled *appliances*. Gas-fired appliances shall be vented in accordance with Chapter 24.

*M1801.2* Draft requirements. A venting system shall satisfy the draft requirements *of the appliance* in accordance with the manufacturer's installation instructions, and shall be constructed and installed to develop a positive flow to convey combustion products to the outside atmosphere.

*M1804.2.6 Mechanical draft systems.* Mechanical draft systems shall be installed in accordance with their listing, the manufacturer's installation instructions and, except for direct vent appliances, the following requirements:

1. The vent terminal shall be located not less than 3 feet (914 mm) above a forced air inlet located within 10 feet (3048 mm).

2. The vent terminal shall be located not less than 4 feet (1219 mm) below, 4 feet (1219 mm) horizontally from, or 1 foot (305 mm) above any door, window or gravity air inlet into a dwelling.

3. The vent termination point shall not be located closer than 3 feet (914 mm) to an interior corner formed by two walls perpendicular to each other.

4. The bottom of the vent terminal shall be located at least 12 inches (305 mm) above finished ground level.

5. The vent termination shall not be mounted directly above or within 3 feet (914 mm) horizontally of an oil tank vent or gas meter.

6. Power exhauster terminations shall be located not less than 10 feet (3048 mm) from lot lines and adjacent buildings.

7. The discharge shall be directed away from the building.

I dug up some old posts on this topic, but was curious if opinions/interpretations have changed any.  What are you allowing/rejecting?


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## mjesse

The air is not being discharged _into_ the soffit, but _through_ it to the outside. Approved, provided a proper termination is installed (hood, deflector, louver, etc.)

Bath fan not a fuel burning appliance, termination separation of 1804.2.6 not applicable.

Concerns about exhausted bathroom air being drawn into soffit vents? ....none


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## steveray

"Concerns about exhausted bathroom air being drawn into soffit vents? ....none"

Rot.....when the moist air reenters the attic and rots the sheathing.....


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## mjesse

steveray said:
			
		

> "Concerns about exhausted bathroom air being drawn into soffit vents? ....none"Rot.....when the moist air reenters the attic and rots the sheathing.....


Really?What happens when it rains? That's a lot of moist air being drawn into the soffit vents.I'm no engineer, but humid air being discharged to the exterior from a bath fan, and being redrawn (now diluted) into the soffit vents is a concern?
	

		
			
		

		
	

View attachment 1109


View attachment 1109


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## steveray

I agree that it is slight, but it is a concern.....It doesn't rain several times a day, every day....Most of our households shower that much....I have seen lots of blackened and delaminated plywood from poor fan discharge...


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## mjesse

steveray said:
			
		

> I agree that it is slight, but it is a concern.....It doesn't rain several times a day, every day....Most of our households shower that much....I have seen lots of blackened and delaminated plywood from poor fan discharge...


So would you allow the soffit discharge location, or require a roof jack?I too have seen many bath vent problems, mostly due to discharging INTO the attic space - 
	

		
			
		

		
	

View attachment 1110


Installers will just toss the end of the pipe into the soffit space and hope for the best.
	

		
			
		

		
	

View attachment 1110


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## steveray

I would allow something similar to the OP with some blocking of adjacent "bays" as long as adequate roof venting was maintained...


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## mtlogcabin

Depends on the climatic conditions in your area


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## JCraver

mjesse said:
			
		

> The air is not being discharged _into_ the soffit, but _through_ it to the outside. Approved, provided a proper termination is installed (hood, deflector, louver, etc.)Bath fan not a fuel burning appliance, termination separation of 1804.2.6 not applicable.
> 
> *Concerns about exhausted bathroom air being drawn into soffit vents? ....none*


That is indeed my concern.  99% of new homes built here have full-vent or center-vent alum. soffit.  If you cut a hole in the middle of a piece of fully-vented soffit, attach a louver to it, and hook your fan/duct to that, you haven't really improved your situation any IMO.  Therefore; the perceived need for solid soffit on either side of the vent termination...

It gets hot here in the summer, and very humid, and it rains.  But I'd venture a guess that even at its hottest there will be much less moist air entering the attic from that, then there would be from someone taking a half-hour long hot shower.  BUT, I'm no engineer either, so I really don't know.


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## ICE

JCraver said:
			
		

> Contractor wants to run the exhaust from bath fans through the soffit to the outside.  If he puts a solid soffit at least 4' in either direction from the center of the exh. outlet (screened louver, etc.), would this then be a compliant install?


I concur that there is a need to implement measures to keep the moist air out of the attic.  Eliminating openings within 4' of the vent termination aught to do it.


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## Pcinspector1

Vent it to the front porch soffit right above the front door should do the trick!


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## Fort

JCraver said:
			
		

> BUT, I'm no engineer either, so I really don't know.


Well in my experience with most engineers, they don't really know either, they are just making stuff up half the time...but they stamp and sign and it shall be so...


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## skipharper

If you recall they use to lay on the soffit and then the change came to discharge to the outdoors. I see several valid points here and keep in mind the changes to the 2015 codes crank up in January so get used to Cdp Access and start submitting!!!


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## Francis Vineyard

To put this in another perspective look at all the other exhaust that can discharged directly underneath a soffit or adjacent to a gable vent. Operable openings are windows; intake openings are not soffits or gable vents.

*R303.4 Opening location. *Outdoor intake and exhaust openings shall be located in accordance with Sections R303.4.1 and R303.4.2.


*R303.4.1 Intake openings. *Mechanical and gravity outdoor air intake openings shall be located a minimum of 10 feet (3048 mm) from any hazardous or noxious contaminant, such as vents, chimneys, plumbing vents, streets, alleys, parking lots and loading docks, except as otherwise specified in this code. Where a source of contaminant is located within 10 feet (3048 mm) of an intake opening, such opening shall be located a minimum of 2 feet (610 mm) below the contaminant source.  For the purpose of this section, the exhaust from _dwelling_ unit toilet rooms, bathrooms and kitchens shall not be considered as hazardous or noxious.



*IMC 501.2.1 Location of exhaust outlets. *The termination point of exhaust outlets and ducts discharging to the outdoors shall be located with the following minimum distances:
1. For ducts conveying explosive or flammable vapors, fumes or dusts: 30 feet (9144 mm) from property lines; 10 feet (3048 mm) from operable openings into buildings; 6 feet (1829 mm) from exterior walls and roofs; 30 feet (9144 mm) from combustible walls and operable openings into buildings which are in the direction of the exhaust discharge; 10 feet (3048 mm) above adjoining grade.2. For other product-conveying outlets: 10 feet (3048 mm) from the property lines; 3 feet (914 mm) from exterior walls and roofs; 10 feet (3048 mm) from operable openings into buildings; 10 feet (3048 mm) above adjoining grade.3. For all _environmental air _exhaust: 3 feet (914 mm) from property lines; 3 feet (914 mm) from operable openings into buildings for all occupancies other than Group U, and 10 feet (3048 mm) from mechanical air intakes. Such exhaust shall not be considered hazardous or noxious.
*ENVIRONMENTAL AIR.* Air that is conveyed to or from occupied areas through ducts which are not part of the heating or air-conditioning system, such as ventilation for human usage, domestic kitchen range exhaust, bathroom exhaust and domestic clothes dryer exhaust.


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## Pfall52

From the residential code.
R303.5.2 Exhaust openings. Outside exhaust openings
shall be located as not to create a nuisance. Exhaust openings
shall not be directed onto walkways. Exhaust openings
shall not terminate within 3 feet of a ventilated
section in a soffit.


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## cda

Pfall52 said:


> From the residential code.
> R303.5.2 Exhaust openings. Outside exhaust openings
> shall be located as not to create a nuisance. Exhaust openings
> shall not be directed onto walkways. Exhaust openings
> shall not terminate within 3 feet of a ventilated
> section in a soffit.




Welcome !!!

How did you find this humble forum??

Looks like you may a a few years of knowledge and experience


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## Pfall52

cda said:


> Welcome !!!
> 
> How did you find this humble forum??
> 
> Looks like you may a a few years of knowledge and experience



Thank You
I found you online with a search. I've been looking for a good construction code forum and it looks like I found it.
Yes I owned a mechanical contracting business for over 35 years and transitioned to inspecting about 5 years ago.
I've been in the building trades my whole life.


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## cda

Pfall52 said:


> Thank You
> I found you online with a search. I've been looking for a good construction code forum and it looks like I found it.
> Yes I owned a mechanical contracting business for over 35 years and transitioned to inspecting about 5 years ago.
> I've been in the building trades my whole life.



Please ask or answer questions


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## mark handler

Appliance | Definition of Appliance by Merriam-WebsterMerriam-Webster › dictionary › appliance2 a : a piece of equipment for adapting a tool or machine to a special purpose : attachment. b : an instrument or device designed for a particular use or function. an orthodontic appliance ; specifically : a household or office device (such as a stove, fan, or refrigerator) operated by gas or electric current.


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## Robert

Francis, thanks for the code sections. I see (and spec) quite a few high-efficiency furnaces with horizontal exhausts (using an integral put-put fan), usually daylighting out the side of the building. Would this exhaust fall under the 10' to property line code section? I believe these are noxious fumes (similar to the fumes that would be expelled through a vertical flue to the roof if using a non-horizontal furnace). Thank you.


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## linnrg

Pfall52 said:


> From the residential code.
> R303.5.2 Exhaust openings. Outside exhaust openings
> shall be located as not to create a nuisance. Exhaust openings
> shall not be directed onto walkways. Exhaust openings
> shall not terminate within 3 feet of a ventilated
> section in a soffit.




My residential code book does not have the last sentence - is this from a specific state code or a local amendment?


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## mark handler

linnrg said:


> My residential code book does not have the last sentence - is this from a specific state code or a local amendment?


Or Is it a different version.


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## linnrg

here are two pics for consideration.  I have looked at these over the years - the first is a clear view of the bath fan termination.  The second shows the beginning of the thaw that I usually see - it is never a big area just a small location of the roof directly at the bath fan termination.  The snow on this roof right now is fairly icy so it will take awhile to thaw.  I do not think is is a good idea to terminate near the vented soffit - but it ain't in my book so I cannot write it up.


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## JCraver

linnrg said:


> My residential code book does not have the last sentence - is this from a specific state code or a local amendment?



It doesn't say that in the '09 we were on when I started this thread, nor in the '15 that we're on now.  

Regardless, I still believe that the intention of the code(s) is to not have an exhaust within 3 feet of an opening back into a building.  A vented soffit is an intake opening directly into the attic.  Therefore, I'm still telling folks that they have to have solid soffit on either side of the vent termination if they do it this way.


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## mtlogcabin

2012 IRC

M1501.1 Outdoor discharge.
The air removed by every mechanical exhaust system shall be discharged to the outdoors in accordance with Section M1506.2. Air shall not be exhausted into an attic, soffit, ridge vent or crawl space.


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## Pcinspector1

2006 IRC, in a different section, M1507.2, Does not list soffit or ridge vent.


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## mtlogcabin

2006 IRC
M1501.1 Outdoor discharge.
The air removed by every mechanical exhaust system shall be discharged to the outdoors. Air shall not be exhausted into an attic, soffit, ridge vent or crawl space.
Exception: Whole-house ventilation-type attic fans that discharge into the attic space of dwelling units having private attics shall be permitted.


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## Obfuscator

Pfall52 said:


> From the residential code.
> R303.5.2 Exhaust openings. Outside exhaust openings
> shall be located as not to create a nuisance. Exhaust openings
> shall not be directed onto walkways. Exhaust openings
> shall not terminate within 3 feet of a ventilated
> section in a soffit.


Which version of IRC is this quote from?


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## Paul Sweet

2018 IRC section 1504.3 says:
"Air exhaust openings shall terminate as follows:

Not less than 3 feet (914 mm) from property lines.
Not less than 3 feet (914 mm) from gravity air intake openings, operable windows and doors.
Not less than 10 feet (3048 mm) from mechanical air intake openings except where the exhaust opening is located not less than 3 feet (914 mm) above the air intake opening. Openings shall comply with Sections R303.5.2 and R303.6."
An eave cap discharges below the soffit, not in the soffit.  The 3 foot distance from a ventilated portion of a soffit might be good practice, but it isn't in the current IRC.


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## mtlogcabin

2018 IRC
M1501.1 Outdoor discharge.
The air removed by every mechanical exhaust system shall be discharged to the outdoors in accordance with Section M1504.3. *Air shall not be exhausted into an attic, soffit, ridge vent or crawl space.*

Exception: Whole-house ventilation-type attic fans that discharge into the attic space of dwelling units having private attics shall be permitted.


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## classicT

mtlogcabin said:


> *Air shall not be exhausted into an attic, soffit, ridge vent or crawl space.*


I'd argue that it is not exhausted *into *the soffit. It is exhausted to the exterior, with a duct that extends through the soffit.

So long as there are not openings within 3-ft of the discharge location, what's the issue? Approve it and move on.


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## Obfuscator

mtlogcabin said:


> 2018 IRC
> M1501.1 Outdoor discharge.
> The air removed by every mechanical exhaust system shall be discharged to the outdoors in accordance with Section M1504.3. *Air shall not be exhausted into an attic, soffit, ridge vent or crawl space.*
> 
> Exception: Whole-house ventilation-type attic fans that discharge into the attic space of dwelling units having private attics shall be permitted.


"Into" signals the code intent, as in "into" a space.  Soffit has a "space" on the inside, not the exterior.  And we've all seen bath fan exhaust ducts just dropped "into" the soffit area, as if the installer was hoping the exhausted air would somehow find a way through the soffit vents.

For example, here is a letter from a NC DOI official regarding related question:


			https://www.ncosfm.gov/media/1018/open


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## mtlogcabin

classicT said:


> I'd argue that it is not exhausted *into *the soffit. It is exhausted to the exterior, with a duct that extends through the soffit.


Perhaps Jar can shed some light on this one since he took the picture (when he worked on the dark side) if it vented to the exterior or just to the soffit. Either way it is easy to see that the moist air came right up the insulation baffle and that is why there should be no soffit vent openings within 3 ft either side of the exhaust opening.


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## classicT

mtlogcabin said:


> Perhaps Jar can shed some light on this one since he took the picture (when he worked on the dark side) if it vented to the exterior or just to the soffit. Either way it is easy to see that the moist air came right up the insulation baffle and that is why there should be no soffit vent openings within 3 ft either side of the exhaust opening.
> View attachment 8523


That looks like it was exhausted to the exterior but right above the outlet was a soffit vent. That is obviously non-compliant and one should cite R303.5.2 or M1504.3 because there is a soffit vent opening within 3-ft of the exhaust termination.


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## Paul Sweet

The section Pfall52 quoted appears to be a Michigan amendment.


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## rogerpa

Correct


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