Using old B-vent / Chimney

[walker]

Off topic question but maybe someone here knows.

I have an old B-vent / Chimney that is capped off not being used for anything anymore and I'm in the process of a having a washroom installed in my basement.  There is no shower/tub being installed so moisture isn't an issue,  I'm having an exhaust fan installed and its a real bitch to vent to the outdoors as I liv ein a townhouse and there much wall space at the front or back to vent through, I have little options on where to go with it, is it possible to just have the bathroom fan exhaust just go to my old b-vent??

I know its not the ideal solution, but just wondering if its against any building codes or anything.  I'm sure I should know the answer to this already, and so should my contractor but I've never come across the idea before and neither has he.

[Admin]

You can do that.  Drop a 6" insulated flex duct down and reduce to your 3" or 4" fan.  You will have to find a roof jack style of termination.  Most new houses have second floor exhaust fans connected to roof jacks.  The old B-Vent is irrelevant.  It's simply acting as a chase for your exhaust fan duct work.

Article 9.32.3.5 of the Ontario Building code can be followed if the duct is less than 30' long.  With flexible duct you would need to use 6" for a 50CFM fan or 7" for a 105CFM fan.

(4) Exhaust ducts serving the required kitchen, bathroom, water closet room and other supplemental exhaust air intakes shall be sized according to Part 6 except that they may be sized according to Table 9.32.3.5. where,
(a) the total duct length does not exceed 9 m, and
(b) the number of elbows does not exceed 4,
but, in any case, they shall not be smaller than recommended by the manufacturer of the fans.

I attached a picture of Table 9.32.3.5.

[walker]

Thanks for the reply.  I managed to get it done through the box of the house,  but I had to remove my A/C lines and move it out of the way.

Good to know for the future that your option can be done.