Do I need a bathroom vent?

[Alex Gordon]

I recently purchased a duplex with 2 2/1 units.  I'm renovating the unoccupied unit.  The bathroom has a heater and no fan or vent.  I'm planning on replacing the small heater but I'm hoping to avoid running a vent to the outside.  I've seen some of the ventless fans that don't appear to do much.  The place seems to have lasted 46 years without mold/mildew.  Do I absolutely need to put in a fan?  Is there something else I can do?  Thanks 

[Bob H.]

Regardless of what old codes say, nobody is going to open the window 99% of the year. It's a matter of whether you want to do things right or do things for the lowest possible cost -- but you already knew that.

It's better to put in the fan. If you do, certainly don't make the fan come on every time someone turns on a light to wash hands or brush teeth. That's unnecessarily noisy, wasteful of electricity and annoying. Instead, put in a switch with a timer that has buttons to run the fan for 10, 20 or 30 minutes.