Basement Bathroom Exhaust

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nerdkingdan

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We have a basement bathroom, we are trying to put an exhaust fan into.
We have some bad options which would you recommend?

1. (won't work) Put the exhaust directly below the kitchen window. How bad would this be? "Never mind on this one(I found the Michigan code prevents it)"

2. Box a small area of the laundry room ceiling out. Reduce the duct to 3" and run it through a small cavity in the floor joist, behind kitchen cabinets, and out a side wall(won't be near a window)
3. Box out a larger area of the laundry room ceiling, then run it through a wall into the attic space and out the roof.


Thanks.
 
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homeowner_bob

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2021 IRC:
M1504.3 Exhaust openings.
Air exhaust openings shall terminate as follows:

1. Not less than 3 feet (914 mm) from property lines.
2. Not less than 3 feet (914 mm) from gravity air intake openings, operable windows and doors.
3. 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.

For the kitchen window, #2 is your potential problem assuming your locality follows this. If it's more than 3 feet, then it's a non-issue. Less than 3 feet - judgement call on how close it is and how much work you want to do re-routing it. Personally, if it were me, I wouldn't put it 6 inches below the window, but wouldn't stress about it being ~2-3 feet away. Assuming the kitchen window is the easiest route.
 
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John Gayewski

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I can tell you reducing the pipe size is bad. Those fans are weak and need full sized ducts to be effective. I prefer not to use flex ducts either due to the reducing the flow. I personally like to have the air move when I want it to move.

Exhausting near a kitchen window isn't ideal due to poop smell while cooking. I guess if you never use the window, but I use my windows so I wouldn't want that. I bet the roof is the best for routing but probably harder to service or clean the duct if ever needed. So side wall it is.
 

nerdkingdan

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I can tell you reducing the pipe size is bad. Those fans are weak and need full sized ducts to be effective. I prefer not to use flex ducts either due to the reducing the flow. I personally like to have the air move when I want it to move.

Exhausting near a kitchen window isn't ideal due to poop smell while cooking. I guess if you never use the window, but I use my windows so I wouldn't want that. I bet the roof is the best for routing but probably harder to service or clean the duct if ever needed. So side wall it is.
Looking at this more, It seems the best option is going through the roof, however I can't find what ductwork should be used for a bathroom vent inside a 2x4 wall. Normally you want the flexible hose to avoid any leaks, what kind of ductwork goes through the wall safely?
 

John Gayewski

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If the appliance is electric it'd be aluminum duct pipe. But I'm not sure what size. If it is 4" you either need to fur or the wall or reduce it which I hate personally.
 
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