Need clarification on bathroom fan

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Keithwh

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Hi All! First time poster, long time lurker.

I need to install a fan in my basement bathroom as part of a basement fishing project.

The shortest route to the outside wall is straight out about 5 feet. This would put the exhaust vent 2.5 feet under a window.

I have read several things about clearances for this fan. Most notably that it can’t be closer than 3 feet to any operable window or opening.

I have also read that since bathroom vent exhaust is not noxious, it shouldn’t be a problem running it to that location.

What is the consensus on this? It will need to be inspected.

Thanks for your reply’s!

-Keith
 

Jadziedzic

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Contact your local Authority Having Jurisdiction and ask them if they are OK with the proposed vent termination location; if they're the ones who are going to inspect it they'll have the last word anyway. I may be overly fortunate, but I've found the inspectors in my city are VERY willing to assist the DIYer who is looking to do work in compliance with local codes.
 

Jadnashua

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Functionally, since it's not venting combustion gasses, it should be fine, but, agree, check with your inspector.
 

Keithwh

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So I checked with my local inspector, and he is not going to offer any leeway as far as placing the vent.
  • Per section R303.3 Bathrooms. Of the 2015 IRC. Bathroom , water closet compartments and other similar rooms shall have an aggregate glazing area of 3ft and ½ which shall be operational.
  • Per section 1506.3 Exhaust opening. Of the 2015 IRC. Air exhaust openings shall terminate not less than 3 feet from property lines. 3 Ft. from operable and non-operable openings into the building
  • And 10 feet from mechanical air intakes except where the opening is located 3 feet above an air intake.
So R303.3 doesn't apply. No window in the basement bathroom. My next question would be is there any code on how bathroom fan ducting should be run? I referred to table M1506.2 in the 2015 IRC (which is what our county follows), for duct sizing. I mapped out the next closest area in the basement, about 25 feet from the bathroom. I am going to be using an 80 cfm fan, and there will be 4 elbows in the run. According to the table I have to upsize to 5" smooth ducting to get to the amount of length I needed.

Does this sounds OK? Other than making sure the ducting is sealed, is there anything else I should be concerned about?
 

Jadziedzic

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Use galvanized metal duct (as opposed to aluminum). Maintain a gradual slope to the outside to allow any condensation that collects in the duct to drain outside (and also insulate the duct to minimize condensation in the first place); this is particularly important if there's a shower or tub in the bathroom. The lengthwise seam of individual sections of duct should face upward; likewise, any screws securing sections of duct should be arranged so none penetrate the bottom of the duct. Support the duct as outlined in the IRC (e.g., every "n" feet).
 

Keithwh

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The run would have to jog down to clear a joist then back up. Will this be allowed?
 
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