According to John Grabowski :

"Aaron Fude" wrote in message
...

How does one install an exhast fan when the joists run parallel to the
outside wall. My prospective contractor recommends drilling holes in
the joists. This is a larger bathroom so I need a larger fan so I am
going to have 6" holes in my joints. Isn't that effectively cutting
them in half? What could be an alternative solution?

You should be able to find larger CFM fans that only use 4" duct. I don't
think gouging out a good portion of your joists is a good idea. Another
possibility is to build a small soffit to accommodate the duct.

Or install more than one exhaust unit so you can use smaller venting.

6" seems rather extreme. IIRC, our main bathroom (9x18) could be
vented properly with one high CFM (220CFM I think) fan with 4" duct
or two fans with 3".

Another possibility is to use multiple inlets with a blower mounted
elsewhere. You could use smaller inlets (within reason) without paying
the noise penalty if the blower is installed elsewhere.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.