Best way to make an attic fan smart?

We are relatively new owners of an old home. When I was crawling up in the attic I saw that it has an attic fan wired to a thermostat such that it would be able to turn on automatically based on the temperature in the attic. The thermostat is dead but the fan can still be manually turned on by a wall switch in my son’s closet.

Rather than replacing the attic fan thermostat, I was thinking of putting a sensor in the attic and replacing the wall switch. What would be the best low-cost way of accomplishing this? I have a smartthings hub and I was thinking I could either use IFTTT or Webcore to automate the fan based on the sensor in the attic.

I’m willing to spend a little extra for a smart setup if it makes sense. But I’m not looking at spending too much since a new thermostat is only $20 and if a new thermostat cannot be wired in then a new combo fan and thermostat is only $80.

I was thinking of an Iris sensor and a GE wall switch. Would this setup work? Any recommendations on setting this up?

I appreciate any advice on products or setup!

It would be a “fun” and educational project to automate the attic fan with SmartThings. But, remember, this requires an Internet connection and you’re at the mercy of the whole SmartThings ecosystem!

Perhaps it would be easier, cheaper, and more reliable to take the Lo-tech approach and just replace the fan thermostat? :sunglasses:


Since it’s just an attic ventilator, I’d just replace it. You don’t really need any functionality beyond what you already have.

  1. it can work. It’s less reliable than a line thermostat.

  2. it does bring the benefit of easy monitoring and notification of this typically limited access space. I did this - a plug-in with power monitoring for the gable fan motor and a wireless temp. But I can hear my fan run anyway - it makes more sense if your fan is so quiet that you might forget about it otherwise. It may also provide warning of high fan amps suggesting impending motor failure.

  3. webCore makes this fairly straightforward to implement for example, turn-on-above-104F, turn-off-below 101F. (my temperature is sensing close to the roof deck).

  4. a fine project as an automation exercise I think. I actually wired the receptacle inline with the original thermostat. Probably not up to code but I like it for the unfinished attic and it was easier than taking it out. I do recommend putting in a receptacle and fitting the fan with a plug since they fail often (3-6 years), if you buy cheap, as I do.

  5. surprised the thermostat failed. There’s not much to it.

I recently put an Iris contact sensor in my attic (suspended from a string tied to a rafter) to get an idea of what was going on up there in the summertime, since I used to have a homebrew ventilator installed but was never quite convinced that it was accomplishing anything. Kind of sobering to see the attic temperatures climb into the 130’s yesterday when it was in the mid 90’s outside. I think I will be re-installing that ventilator now that I can see what it will be doing.

Also made a WebCore piston to display ‘rising’ / ‘falling’ / ‘steady’ temperature indicators (over a 10 minute sampling period) which may be useful in deciding when the fan should run (or if it is doing anything at all). I currently have a whole-house fan controlled by a GE 14291 in-wall smart switch that works well in that application; will probably use something similar for the ventilator.

I thought about doing this because I recently had to replace the motor in my attic fan. The thing is loud but instead of automating the fan via ST per se, I replaced the dumb switch with a GE Smart Switch. This way, if it was annoying by being on with no other house noise to block it, we could easily turn it off.

I set up a rule to turn on the switch every morning at 7am.

Taking it further, since I did put a spare contact up there to monitor temperature, I guess all I would have had to do is create a webCoRE rule such as.

If temperature is greater than or equal to 100
Then with Attic Fan Switch
Turn on
Turn Off

However, not to over complicate things, I just purchased a new inline therm so it could just do it’s thing without the “Smarts”.

Re: surprised the thermostat failed There’s not much to it.

Yeah, I didn’t even know it had a thermostat in line until I went up in the attic. I thought it just worked off the switch. I didn’t do any significant diagnostics on the thermostat but it never seems to turn on automatically no matter how I adjust the temperture dial. I just figured it had died since the fan sill worked fine.

Thanks for the feedback!

LOL! Where is the fun in that?! :stuck_out_tongue_closed_eyes:

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You can definitely use a simple sensor and then create an automate rule to turn on/off the fan based on the sensor.

Another way to control it would be to limit when it runs using a smart switch only, if you have access to RBoy Apps check out this SmartApp: