Client always resist 1 gap over the floor covering.
Gap under bathroom door for ventilation.
My contractor just hung our fancy dancy un painted solid wood door slabs in my 100 year old house with solid hardwood floors throughout.
I think it is too big and think a 1 4 1 2 gap would accommodate any unevenness in our floors and allow us to use area rugs.
The flow dropped from an unrestricted 150 160 cfm down to under 100 cfm in each room.
I have a problem with the door vents you are passively promoting.
This is less than desirable in bathrooms and bedrooms.
Check your bathroom door.
There is a need for an air gap at the bottom for ventilation.
7 mistakes not to make in your bathroom remodel do let your.
A 10mm gap under the bathroom door is very usefull it allows the fan to work easier as it can draw in air and because its from within the house it stops the bathroom.
My mom has a house with a central return and as you suggest her doors have about a 1 5 gap underneath to allow air to flow.
If the bathroom vent can t get any air of course it isn t going to work the right way.
If your door has very little or no clearance at the bottom you.
However the size of that gap is very unlikely to be greater than 1 2 for any door.
There is an approximately 1 5 gap at the bottom of the doors.
And for proper bathroom ventilation your exhaust fan needs to vent outside not into the attic or another area of the house.
I like the suggestions for wall ceiling jump ducts etc.
There should be plenty of room under the bottom of the bathroom door to allow air to get into the room so the fan has a source from which to pull the air it needs.