I also started with a simple flow, but in real life this can’t be covered by a simple flow.
I have an advanced flow that’s based on the Flow in this and this post, cause in the winter or on a very rainy day the humidity of the bathroom can be very high and that would made my ventilation system run for hours or even days. Just like Hugo said.
So basically Homey needs to know if someone is in the Bathroom, and using the shower or even the toilet (we also need to get that nasty smell out 
). Homey knows if it’s a short bathroom visit or a long visit. No need to turn the ventilation on when we do some quick things and leave after seconds or a view minutes.
When Homey knows bathroom is in use for showering, get the Average humidity before showering, then calculate the Limited humidity for an exactable humidity (humidity you want, is exactable after using the shower). So now Homey knows when the bathroom is above the Average humidity the ventilation goes on. And when the limited humidity is reach the ventilation can turn off after a view minutes when reaching that limited humidity.
Ventilation and lights are controlled by this advanced flow.
