On 17 Nov, 19:27, wrote:

You could combine ducts and then have one fan sucking from both
rooms.

I could, but that's not my plan - I already have a ceiling fan in
place in the upstairs bathroom, waiting to be connected to the
chimbley, which is also in place.

David in Normandy wrote:

I've recently fitted a bathroom fan that vented to the eaves space. I
found two problems:

I'm not surprised you had condensation and damp if you were venting
into the eaves. I propose to vent to the outside.

Thanks for all the thoughts, but I'm still hoping someone knows
something about my specific question, concerning two fans blowing up
two ducts that meet at one chimbley ;-)

http://oscarthecat.fotopic.net/p54956795.html


Regards
Richard