HELP for ventilation system flow

I’m new to Homey and I don’t really understand how flows work…
I just have a Homey bridge for beginning.
I’m looking to do something simple to start with.
If my bathroom humidity sensor is above 65% then activation of the ventilation.
If my bathroom humidity sensor is below 60% then desactivation of the ventilation.
My sensor and the activation of my ventilation are done via XIAOMI equipment which is well integrated into my Homey but impossible to manage to configure this flow.

Exemple :
Sensor > 65%

??? All the day ???
??? Every 56 minutes ???
I don’t know what to do here

Activation of ventilation

I’ve try that, but doesn’t work :

Thanks !

Looks like you are trying to do it with 1 flow, which is not advisable.
Create for both situations another flow.

[IF] humidity gets higher the 65 [THEN] turn on
[IF] humidity gets lower then 60 [THEN] turn off

And don’t connect them too each like you show now, keep them separate.


I’ve also try with 2 simple flows :

But it’s still doesn’t work, i have to lunch manually the flow.
The goal is for it to be automatic.

The flow does only activate when the trigger is happening, so when it actually goes from below the value, to above the given value.
If you want it to keep activing then you should look at something like.
[IF] humidity changes [AND] is higher then 65 (this is a logic card) [THEN] turn on


OK ! I’ll try that :slight_smile:
I just need to understand the “logic” of Homey and I think after it will be ok :slight_smile:

I think I’ve understand :

If humidity change → Check if superior at 65% → If yes, so activation of ventilation / If no, so desactivation of ventilation.

And that kind of flow will be active all the time?
I mean as soon as Homey detect a variation of humidity he will start the flow ?

That is indeed what that trigger card does.
Do keep in mind that your latest flow might start to toggle a bit, if it goes above and below a few times, it is better to have at least 2% of difference between on and off.

Thanks for the tip !

I think it’s better now :slight_smile:

And what if the humidity outside is over 65%?
Maybe you should do it like:

Make variable “bathroom humidity”
Fill variable with humidity from sensor.
If humidity has changed and difference is more than 10%:
Start fan.
If humidity has been the same for 10 minutes:
Stop fan. (Counter app)
And fill variable humidity with humidity of sensor.

This way your fan is not going to run constantly if the humidity outside is high.

1 Like

I’ll try something in this style.
But my bathroom haven’t any windows or natural ventilation, that’s why it’s not a problem at all if the ventilation is running a long time a day.

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 :joy:). 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.

1 Like

At the risk of confusing with too many options, I have been using this solution happily for several years. It uses a single variable and no special apps. I found that in practise, any rise of more than 1% in humidity in 4 mins (which is the max reporting frequency of my sensor anyway) only happens when the bathroom steams up and never false triggered by background weather changes. Also, once the fan is on, I found that the point at which the measured humidity starts to fall is about the right time to turn it off, given my fan has a built-in overrun of 4 mins after I turn it off. So you might need to tweak the specifics based on your scenario but maybe this is an alternative simpler approach than some of the others that could work for you.


Try that

substitute multi-sensor for your sensor
substitute attic bulb for your fan

1 Like

This is how i do it.

I calculate the average humidity every 10 minutes with a humidity sensor in the bathroom.
I add 5% to that. When the humidity of the sensor has exceeded the maximum, the ventilation is switched on.
When the value is 5% below the average humidity, the ventilation switches off.