Pre-purchase questions re: humidity control

Hi there. I'm new to DIY home automation. My experience is limited to Alexa, smart light switches, and wifi thermostats. I ended up here from a random Youtube comment, and I'm liking what I'm seeing in Hubitat, but I am looking for more info prior to committing.

I have a Nest thermostat and I'm starting to hate it. I've put up with it for about 3 years, but it's getting to the point I want to rip it off the wall. I recently installed a whole-house steam humidifier which is wired to the Nest because Nest brags about having automatic humidity control. Well, "automatically" does not mean what I think it should, because the Nest does not anticipate cold weather or reduce relative humidity when the temperature drops. I end up manually toggling the humidifier on and off constantly to prevent condensation on windows.

Anyway. I started getting more into a way around this, and my current thought is to try to automate this as much as I can. I'd like to put several humidity sensors throughout my house so that I can get an average level throughout, and then be able to tell a smart thermostat whether to run the humidifier or shut it off. I'd like to be able to build logic in to check the forecast and reduce the target humidity if cooler weather is expected to prevent condensation. I want to use distributed sensors because for some reason the humidity level at the thermostat seems to drastically different than other areas of my home.

My questions:
-Is this a doable workflow with Hubitat? Has this been done before?
-What is involved in making this work? What kind of scripting/code knowledge do I need here?
-What hardware might I need? Is there a preferred humidity sensor that I can throw into multiple rooms?
-Is there a thermostat that I can use that will allow me to intelligently turn the humidifier on/off? IE can I get rid of this stupid Nest? I've looked at a few zigbee enabled thermostats but I'm having trouble determining if they allow for remotely controlling the humidifier outside a native app.


If you are just turning a humidifier on and off based on humidity sensors, do you need a thermostat, or will a smart switch be good enough?

It's a whole house humidifier, attached to mains and integrated with my HVAC system. IE it's not a standalone appliance, it's like controlling the furnace or AC.

I think you could do this, the question is how do you control the humidifier. Does it still happen via the nest, or is it on a separate relay/switch. You only want that humidifier running when the furnace is calling for heat.

I have an older beige ecobee that handles all of this perfectly, using outside temp skewing to prevent frost on the windows when it gets cold. But I don't know if the newer ones do this.

It's currently done via the Nest. The Nest is set up so that when the humidifier is on, it knows to start the blower fan on it's lowest setting. Currently, the humidifier can run on it's own, with or without the furnace burners going.

That's why if the Nest gets gone, I would want a thermostat that will accept input from Hubitat to turn the humidifier on or off. In theory I can have the logic of how much the humidifier runs done externally, if I can install a thermostat that will accept that external control.

As an aside, I understand that warmer air can absorb more moisture, which I think is why you're saying to only run it when there is a heat call. However, in my home the furnace runs very rarely (we keep it set to like 62 most of the time) so that's not enough run time for the humidifier to do its thing. So far it hasn't been an issue. In the summer, when the AC is going, we will have the unit shut off so there are no issues with the ducts sweating.

AFAIK, there is no z-wave/zigbee thermostat that supports a HVAC accessory. That being said, Hubitat has three different integrations for the ecobee thermostat, which does support accessories like a dehumidifier/humidifier. I think that at least with @storageanarchy's Ecobee Suite for Hubitat, it should be possible to control the humidifier via Hubitat.

There are several people here who have ecobee thermostats and speak well of them.

I use a Nest thermostat, I actually like it. It's the "E" model so it does not do the humidity.
I use a Zooz Zen16 relay to enable/disable power to the solenoid valve on the humidifier attached to my furnace.

I use RM for the logic using the average of the Nest thermostat and some other humidity sensors around the house compared to the target humidity calculated with this app- [Release] Ideal Indoor (Winter) Humidity Calculator - Developers - Hubitat

This is the old driver and I pretty much use the same logic you have to dehumidify. I can control my nest with hubitat, aggregate humidity sensors, and toggle on my DeHumidifier. If you need to seperately wire up your humidifier, I do recommend the zen16, although you might have the option on your nest driver page if it's already hooked to that.

I have 4 ecobees and do love them but I HATE that their api is cloud based. I’d say they have at least outage a week of at least a few minutes. That means it misses some commands sent from hubitat which can be problematic. For example I have rules to turn off the heat if I leave doors open and turn it back on when they’re closed. Well I’ve had times where it got the “off” command but not the “on” and I don’t notice my heat is off till it’s freezing inside!

1 Like

This might not be to your taste, but I believe there are people here who control them locally using Hubitat by the following method:

Connect using HomeKit to the Home Assistant HomeKit Controller. Using one of the Hubitat MQTT apps to pull them into Hubitat as a virtual device from Home Assistant.

Yeah. Unfortunately in addition to being complex, that won’t work with Ecobee Suite :confused:


Just earlier today, I think @SmartHomePrimer was stating the desirability for Hubitat to have something like Home Assistant's HomeKit Controller.

You have just raised a second use case for that desirability.


I controlled humidity in our former home (sold in 2019) using a steam humidifier connected to an Ecobee thermostat but with some additional safeguards in place (sail switch to make sure the HVAC airflow was present running before the steam humidifier could start). I've tried using the ecobee alone as the controller, which worked well enough, and I've tried using an automation controller (not an HE in that home), which gave me a bit more precise control and the ability to control things locally rather than through the cloud.

I have not tried this using Rules Manager but see no reason it could not be done. You really just need a switch to turn the steam humidifier on and off (perhaps a relay control wired into the relay of the humidifier, OR just use the relay on your thermostat) and the ability to turn the blower on the HVAC on BEFORE - repeat, BEFORE - the steam humidifier can start. I found that manually wiring in a sail switch worked perfectly because the circuit to the steam humidifier's control (not the part carrying the load, but the relay control) couldn't close unless the sail switch detected airflow. I can't emphasize the importance of this enough with a steam humidifier, as they can wreak havoc on an HVAC unit if there's no airflow. Anyway...

If you have that part solved, you can likely just keep your cloud connected thermostat if you wish, assuming there is a HE driver that can tell it to turn the HVAC fan on and off. Or, if you want to go local only for that, I find a GoControl z-wave thermostat to be very simple and reliable, but they don't have humidity detection or humidifier control built in.

For the humidity and outdoor temp sensing, I would try a single, centrally located humidity sensor before I spent much time trying to average multiple sensors, which I have always found to be an exercise in frustration. I currently use a Zooz 4-in-1 sensor to check humidity and it remains close to the humidity shown on my Davis Vantage Pro 2 weather station's (ridiculously expensive) indoor unit. Throw in an outdoor temperature sensor and a Saturday morning's worth of writing things up in Rules Manager, and you have an exceptional system. I always tended to use the current outdoor temp rather than the forecast temp because that allowed me to avoid the cloud altogether if I wished. Bit it shouldn't be hard to use the forecast low temp if you wish, instead. Definitely worth trying that out.

With all this done, you should have a system that gives you good control of your humidifier while also having the necessary safeguards in place for a steam humidifier. Those things work really well if you have them set up in a system with great airflow, but if you aren't careful they can create massive problems. Airflow is THE big key, in my view, and too many people don't put in the safeguards to make sure that's present before moisture is introduced. Seriously, a sail switch that won't allow the humidifier to turn on unless it detects airflow could be your best friend one day.

1 Like

Your humidifier should have came with something like this:

Which mounts in your cold air return. It also relies on an outdoor temperature probe. That should easily automate your humidity based on humidity coming back through the cold air return and outside temperature. If your system didn't come with one of these they aren't that expensive and completely automate this for you.


I tend to agree with using one of these.

While Hubitat probably can automate a humidifier, there are much easier and more foolproof ways to do it, like the humidistat above. Or a good thermostat with remote sensors.

While I would like to see more people use Hubitat, and see cool projects done with it, I suggest that this isn't the best use case for a Hubitat, or any smart hub for that matter.

Much like people relying on Hubitat to be a thermostat, there is lots of potential for things to go wrong if Hubitat were to fail, if things weren't programmed correctly, and so on.

"It's just a humidifier" you are saying. But a humidifier that runs unchecked can cause some very serious damage to your home. There is huge potential for mold, rot, and other severe structural damage due to water. Most homes are leaky enough (air-wise) that all the moisture you dump into your home ends up in the walls, attic, windows, and other cold surfaces where it condenses and causes damage.

Thanks everyone, there is a lot of valuable information here and I have a lot to go one/think about. I appreciate all the responses!

My unit did indeed come with one of these. I didn't use it because I wanted the ability to remotely control it rather than having to go into my basement every time I wanted to see what was going on or to make an adjustment. I may just end up using it after all. Thanks.

The new Vivint panels actually support humidifiers. Just installed one into my sister’s house that has it built in! Makes me sad my old one doesn’t.

1 Like

Once you have it dialed to where you want, you really shouldn't have to touch it. You COULD use humidity sensors around your house to help tune it though! However I've found mine to be very accurate and easy to adjust.

1 Like