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?

 

[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

 

[steveray]

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

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

 

[mjesse]

"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

/monthly_2014_10/p_SCW_220_02.jpg.1ce28ecc4bdecc917d3767b6dd3ef11d.jpg

 

[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...

 

[mjesse]

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

/monthly_2014_10/bathroom-vent-discharging-into-the-soffit-causing-mold-growth.jpg.4f6b7e101c1219034ef67c38c81e6a8e.jpg

 

[steveray]

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

 

[mtlogcabin]

Depends on the climatic conditions in your area

 

[JCraver]

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.

 

[ICE]

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.

 

[SCBO1]

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

 

[Fort]

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...

 

[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!!!

 

[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.

 

[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.

 

[cda]

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

 

[Pfall52]

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.

 

[cda]

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

 

[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.

 

[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.

 

[linnrg]

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?

 

[mark handler]

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.

 

[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.

 

[JCraver]

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.