Whole House Fan (Switch)

Take a look at this. I’m not using it but others are, and it seems to work for them:

Thanks to @amn0408.

Thanks @bravenel. The SmartApp is currently going through the approval process at SmartThings but you can get the latest code on github.

@hutchins79, you can use the app to turn on and off the fan (or any outlet or switch) based on a temperature setpoint (any sensor reporting temperature). You can make that setpoint dependent on what mode you’re in (home, away, etc.). I haven’t tested with only having cooling devices without any heating devices. Let me know if you run into any problems. At the minimum you can put in heating settings but not use the heating mode.

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Hi Brian (@Dianoga),
Were you ever able to add code to check for open windows? I was about to start poking around to add that to your code, but it doesn’t make sense if you already did it.

I think I’m also going to make the app lock to specific mode(s), that way I can have different settings for night vs day vs away.

Hi All,

I have an need where the Whole House Fan by Brian without the thermostat meets almost all I need. I have an attic fan (not a whole house fan) and am using the code with a temp sensor outside and one in the attic. I trigger the attic fan when the attic is above a minimum temperature and the outside temperature is less than the attic temperature.

I would like to add one more bit of functionality. I would like it to trigger the fan only when 1) the attic temp is above my setpoint (app does this already) and 2) when the delta between the outside temp and attic temp is greater than a value I set.

I am missing number two. I have cases where the outside temp is 102F and the attic is 103 and it will turn on. Not much will happen here. I would like to set the minimum temperature to say 95 but only turn on if the difference between the inside and outside is say 10 degrees so the fan can actually make a difference by pulling in substantially cooler air.

Is this something someone can help me code and modify Brian’s code?

Thanks all! I am new to this and love it!

This is awesome! I would love to see it tied to an open window and the GE multi-speed switch. I’m toying with the idea of a QuietCool whole house fan and trying to figure out some automatic venting.

At first I was going to try and have my Ecobee3 control it but I think overall having SmartThings control it is best. But as I type that it might be cool if Ecobee would show the house fan usage as part of it’s reports…

note update in my second post…


Hey Brian,
I am looking for something like this to monitor 2 different temp sensors and trigger a fan to vent out hot air from my garage (to save money on AC/electricity bill; same basic idea as a whole-house fan, but in garage; will eventually be doing something similar for the attic as well, but starting here first).

Is there any chance you would be willing to create a modified version (or show me how; or point me in the direction for where to go to learn how) of this SmartApp that doesn’t require the house thermostat (I had it all set up and just about to work, but then it wouldn’t work, because I don’t have a smart thermostat, and don’t need it in this particular project anyway)?

In my case, since this will be in my garage, the house thermostat won’t be involved. So, I just want the other parts. i.e…

  1. Monitor two temp sensors (one will be inside, at the hottest part of the garage, and the other outside; possibly just using the SmartWeather Station Tile which is already configured and ready for use in my ST system)
  2. If outside temp is lower than inside temp, turn switch on.

I already have all of the smart and dumb equipment that I need for the project (including a dumb fan, smart temp sensors, and a smart power switch). All have been connected to and are functioning properly with my version 1 SmartThings Hub.

Also, I already have a thread for my project (Dual Temp Monitoring Garage Cooling Fan System). So, I am already in the process of refining what’s all going to be involved. Now I just need to get the SmartApp part figured out, and your app looks like the closest thing to what I need among apps that are already out there, ready to go.

If I can get some help with this SmartApp aspect, I could begin saving a little money (less heat in the garage means less heat in the bedrooms above it and the rest of the house it is connected to, which means less electricity needed for AC to keep the house cool) in the very near future. :slight_smile:

UPDATE: Actually, I think I got it figured out.
I just copied the code for your SmartApp, identified the portions that I thought weren’t needed (including those relating to both the thermostat and the windows/doors), removed them, resaved, and republished (for just me, of course). Now it is working! :slight_smile:

So, thank you VERY MUCH!!!
This is so cool!

One more thing though…
Is it possible to configure it to trigger on a relational difference instead of just a pure difference?
e.g. instead of triggering on whether or not one temp is higher/lower than another, can it be more sophisticated and trigger on the temp of one being ‘at least’ 5 degrees different?

I don’t know if it actually matters much, but I’m thinking it may help minimize the time spent running the fan when the benefit would be negligable…or is it definitely better to just have it based directly on the higher-than/lower-than idea?

I recently wrote just such an app for the very same reason. Funny thing is that I discovered that the exhaust fans I have are actually worthless, and don’t reduce the temperature at all. Boohoo.

The app, Garage Vent Fans is on Github:


Very cool.
I see the differential value. So, does that mean that it will only trigger if the outside is x-degrees cooler than inside the garage? Also, can that variable be changed from the IDE, or do you need to do it in code and paste it in there? No big deal…just getting to know how this all works.

Yes, the fan will come on only if (a) it’s above the threshold temperature (so you’re not running the fan when it’s cold outside) and (b) the differential between inside and outside is at least [differential] degrees.

You set the threshold and differential in the app itself, when you install it. You can always update the app once installed to change those settings.

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Good to hear.

I will install a copy of yours, and test them to see which I like the best. Since yours has the differential item, I assume that will be a better way to go.

Out of curiosity, what region do you live in, and what temp do you use for the threshold? I mean, I see 75 in there as the default, but I’m just wondering if that’s exactly what you use, or not.

Thanks, Bruce.

Haha! I live in Scottsdale where for many months a year the temps in my garage are in the 90s. So the threshold was pretty irrelevant for me. I replaced two old thermostats for two fans, and those thermostats maxed out at 90, so the fans ran continuously. I figured out that meant they were actually heating the garage, drawing hotter air from outside. So I put in Aeon micro switches, and this app.

I monitored the garage temps for a few days with the fans off back in July, when it was about 98 in the garage. Then I put the app in and monitored the temps. The fan only ran for about 6 hours after 11 pm. The temps with the fans were identical to those without. So, now, the fans just stay off, a total waste.

It’s easy to over-think these things!

Thanks, Bruce.
Makes sense. Bummer in your case though.

In my case, I just tracked it for a day with the temp monitors and switch in place, and got confirmation on something I’ve known anecdotally for a long time…even though the outside temp was much cooler than the temp inside the house all night long, since there was so much heat built up in the garage (and attic, of course; which I will deal with too) the whole night, the house AC had to keep running all night too.

I’m assuming that when I finally get the fan installed, this will change. The temp outside lastnight would certainly have been cool enough and enough of a difference to cool down the garage. I just haven’t been able to test it yet. Now that I have all of the hardware on-hand, and now that I have these SmartApps to test with, I should have some real-world data on the cooling effect of the garage heat exhaust fan by the end of the coming weekend (which is most likely when I will be able to do the fan install).

Due to that “baked-in” heat load, I’m fairly certain one would need to move A LOT OF AIR to actually cool very much. A typical ceiling exhaust fan, like for a bathroom, just isn’t going to do anything. It isn’t just the air that holds heat – it’s the entire structure. I bet the concrete floor of my garage heats to within a couple of degrees of ambient, or certainly of average ambient temperature. You could blow cold air over that all night and not move the needle much.

You put technical knowledge and words to issues I’ve wondered about.
I have long realized that the structure of the garage and house itself will also hold heat. In that way, your point makes sense. Here is what I am thinking…again, without a technical understanding of it…

Since the problem for me is the heat which is radiating outward and upward from the garage into bedrooms above and other rooms behind and around on one side, it seems like a constant flow of fresh, cooler-than-garage-temp air through the room, from the cool low side up through the middle to the upper high spot on the opposite wall may be enough to remove a significant amount of the heat; if it can’t build up because it’s constantly being dragged out by the fan (I got a 740CFM centrifugal inline fan; may connect some ducting later, depending on configuration i use for this down the road), then it can’t radiate into the rest of the house.

Am I crazy, or might this work? :smile:

Hey, if I was that technical I’d give you the BTU calcs to do, but I don’t have a clue. A/C is expensive because it takes a lot of energy to move heat out of a heated space, which your garage effectively is. I would not have high hopes for this getting the relief you seek, but then I’m jaded by a really hot place, AZ.

OK, but remember, I’m not trying to make the garage a nice, cool place to be; I’m simply attempting to limit the amount of heat there is in there that can be transferred into the house. I’ll come back and let you know how it’s working (or not) once I get the fan mounted…

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What kind of whole house fan? Did you install it yourself? Is there also a damper? Is the damper controlled by a switch? Is it insulated so that there is no heat loss in the winter?


I installed this:

QuietCool is what I would like to pick up myself. I’ll probably work to get one in place over the winter so that it’s ready for next season.