Exhaust fan turn on "if" humidity is higher than Thermostat

Hi, Newbie here to this platform but familiar with smartthings, IFTT, and other platforms. I have a bathroom exhaust fan and a multi sensor with a humidity sensor in a bathroom. I would like to set up an app for the Exhaust fan turn on when the humidity in the bathroom is higher than the humidity at Thermostat T-6. Then turn off the fan off when the humidity reaches either the same humidity as the T-6 or a few percent above. Any ideas how to do this? -Thanks!

Welcome to the Hubitat forums.

I would try a couple of the community based bath fan apps, there are a couple that can do this comparison quite easily. I think they are in Hubitat Package Manager which would be the easiest way to install them.


Thanks! That's a big help.

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To add to what @neonturbo has indicated, I want to mention that this type of automation is very simple to do in the built-in application Rule Machine. Here's an example of a rule to accomplish what you want:

Screen Shot 2022-07-10 at 6.59.35 PM

This rule is triggered when the humidity sensed by one sensor exceeds that sensed by another. The state of a private boolean for the rule is used to ensure that a second iteration of the rule doesn't start until the first iteration completes (i.e. it doesn't get triggered again while currently executing).


Thanks! Looks like moving here from smartthings was a good move! Great hardware and evening better folks to help figure things out.


I would also look at this tutorial. Feel free to skip to 2:50 if you already know the basics but the comparative humidity rule building works well.

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I can't say I have gone through this type of setup myself, but wouldn't there be times where you won't want to have the fan running? If this air is more humid outside than in the bathroom, for example. You will either be drawing in more humid air from outside or dryer air from the rest of the house, reducing the effectiveness of the air conditioner.

Well in the video (and my case) it's simply equalizing the humidity from the bath (which will have higher humidity after a shower or bath) where as the humidity in the hallway will be lower. So you're exhausting the humid air of the bath to the outside and drawing in the dryer air from the hallway which once they reach a relative equalization the fan turns off.

Note: Rereading your message I should clarify most bathroom fans (or fans in high humidity areas) are exhaust fans not intake fans


Forgot one. I took SHF app and added the offset feature among others, which OP is requesting. Not an official release yet but I have been testing it and it works great. Need to get it over to the original dev or post it as a new app.

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