Dual Temp Monitoring Garage Cooling Fan System

[Note: I will eventually do something similar for the attic, but for now, starting with the garage, because it is the bigger problem]

My garage is WAY too hot in the summer, and I know it’s rising up into the rooms above it, and radiating out into the parts of the house it is connected to. As a result, we are spending more money than we should be to keep the house cool with AC. So, I am working on a system of multiple projects to help prevent and mitigate this heat problem.

First, I am going to install insulation (both on the big garage door, and on the walls and ceiling where it is lacking.
Beyond that though, I am also going to create a ventilation system in there that will recycle the air with fresh, cooler air from outside at night. So, that is the project this thread is about.

The plan…in general…

I will cut holes on both sides of the garage (one for cooler air to come in and the other to force hot air out).
There will be material of various kinds installed at the holes to prevent rodents, insects, etc from entering the garage through these holes.
There will be a fan on the hot side to force air out.
There will be two smart temp monitors; one on the inside of the garage near the hot air exit vent and one on the outside near the cooler air intake vent.
There will be a smart power outlet/switch at the fan.
Desired program = If the outside temp is cooler than the inside temp, turn the fan on.

Of course, it will need to be more sophisticated than just that, but I think those are the main points.
Here are the details…

A. Vents

  1. Cut two holes (of ‘x’ size) in the exterior walls of the garage;
    a. one high up in the garage on the hottest side of the garage. This is where the hot air will be forced out.
    b. the other close to the floor, on the coolest side of the garage. This is where cooler air will be drawn in.
  2. Install bars/screen/mesh material to help prevent any unwanted visitors.
    a. bars or something big and tough to stop large rodents and/or humans
    b. mesh of some sort to keep out the small rodents and other animals as well as larger sized insects
    c. screen to prevent entry by tiny bugs/flying insects, etc

B. Fan
I have a squirrel-cage fan that I could use for this project (used once years ago to bring cool air from the AC unit via drier vent ducting to other parts of an apartment that only had a window AC unit), but I’m not at all sure whether or not it is an appropriate type or power level for something like this. What do I need to look for as far as power requirements, fan speed, etc? Does anyone have any specific suggestions for doing this kind of thing?

C. Temp Monitors

  1. Outside temp monitor
    a. must be smart so it can be controlled by my STv1 hub
    b. it will be partially protected from direct rainfall/hail hitting it under a deck, but not from getting wet or cold.
    c. either battery or AC-powered could work. I would prefer battery-powered if they don’t need to be changed very often.
  2. Indoor temp monitor
    a. must be smart so it can be controlled by my STv1 hub
    b. it will be in the garage. So, completely protected from outside weather, but it will be in a location where it gets very hot in the summer.
    c. prefer AC-powered unit since it is inside the garage and I can easily string a cord up to it

D. Power Outlet/Switch
Must be smart so it can be controlled by my STv1 hub

Do you have suggestions/recommendations for specific hardware?

What about SmartApps?
I think I saw a SmartApp for an attic fan setup one time, but not sure where that is now, or whether or not it would work for what I’m trying to do here.

Are there any details I’m leaving out?

Is there anything else you can think of that could make this system better?

One suggestion as you are just getting started: SIMPLIFY

First: You need to get the EXTREME heat out, so you really don’t need precision temperature, at least not for outside. For this, I suggest using the nearest weather station’s data, rather than deal with both an external and internal themometer. See the SmartWeather device in the IDE for this (ST uses WeatherUnderground, and you can actually specify which station you want by putting “pws: IDofStation” in place of your zip code in the preferences - otherwise, ST will just use the one closest).

Second: garages are rarely well-sealed, for no matter how hard you try, that big door is going to leak air. So, you might not need the air inlet hole - it may suffice just to pull outside air in through the natural gaps. You can decide later if you really need another hole in your garage. Not having the second hole will help with #3 below

Third: consider the winter. (ignore this if you live where it rarely freezes). The holes you create to move hot air out and cool air in during the summer are going to let frigid air in during the winter, and you probably don’t want your garage to be below freezing if you can avoid it. So, you’ll probably have to block off the holes in the winter… thus (marginally) easier if you only have the one (exhaust) hole.

Fourth: As to fan size, take a look at how bathroom vent fans are sized (cubic feet per minute). You need to figure out how many times an hour you want to replace ALL the air in your garage, and buy a fan that meets those needs. I suspect you’ll want one of the smaller whole-house attic fans for this.

Finally (best for last), although automation always adds a fun-factor, you might consider getting one of these solar-power attic fans http://www.ussunlight.com/products/solar-attic-fans . Get the one from Costco that comes with the temperature remote controller, cut your hole, install the fan, plug it in (runs the fan intermittently at night), and you’re done. You can turn it off in the winter, and/or allow it to be both heat AND humidity driven (clever, no?). I have several - they work great and as a bonus they are VIRTUALLY SILENT (you won’t find an AC attic fan that can claim this - I tried).

FWIW, you will likely find that the outside air is either always cooler than inside your garage, or almost the same (at least in the summer), so you can pretty much skip trying to base this off of temperature differentials…

No matter which way you go, good luck with your project!

You must live somewhere that has cool air outside… :smile:

The first obvious thing that comes to mind is insulation… insulate the garage door and the ceiling if you can, walls if you can as well… Anything will help, spray foam is best but expensive… It’s amazing the difference THAT alone can make. Keeps your garage from being a solar powered easy bake oven… Next is moving air… I would take an “up and out” approach if I could… think whole house attic fan style… then out through a gable vent or roof mounted exhauster… Alot of the design restrictions would be based on if you have a homeowner’s assn, care what it looks like (two side exists might look like something off breaking bad!) and of course your budget… Another thing you need to take into healthy consideration is are you planning on any flammable vapors being present? If so, ventilation needs change a lot, not for health even, for explosion proofing. If you put the right mixture of flammable vapors and air past most electric motors you can ignite it… They make explosion proof fans, but if you’re not going to use those, you just need to move a lot more air than explosive vapor and that can mean a LOT of air… Think of square footage of the garage when considering CFM capacity of the fans as well. Having a purely linear flow from two side exits isn’t likely to do a LOT to cool the inside of a box. You’d want more distributed flow and again preferably a top exit for the hot air. I’d envision even just cracking the garage door, and having a ceiling mounted fan going.

I’ve thought about this a lot, even considering a mini split AC for my garage here in Houston. Part because it’s just too hot outside for a fan to cut it, and its so damn humid as well the sweat doesn’t usually help you much! But I work with a lot of hazardous chemicals like paint thinners, various sprays, etc, so ventilation is already a need, and AC alone wouldn’t be of continuous use for me…

Anyway, not trying to write a novel, but some thoughts…

Only remarks on your sensor setup I’d say is keep them well shielded from the sun or dripping water to keep them accurate.

Totally agree with the advice to simplify.

IMO do not cycle the fan over the internet. Just use a line-voltage thermostat, which is also cheap. And monitor it with ST sensor if you like, might as well put a motion&temp sensor in there.

Before cutting holes in your garage, try a proof of concept. Wait for a typical hot problem day, let garage build up the big problem heat load. At nighttime when it is “cool”, open the existing hole (garage door) and start a mocked-up box fan with intake ducted by cardboard boxes, a short distance from the “cool outside” of the garage. If you have a window or door to the cool outside of garage then use that (blank off the rest of the window). If not, then ducting a short distance left, right or straight from the garage entrance will probably work as well. It’s a cool night, right?

That should tell you if permanent ventilation equipment can help.

You bet the attic is hot too, and adds to your cooling load, over more area than the garage.

Insulation is a good idea, but IMO insulating the garage door and outside walls, will be a big mistake. If your garage interior walls and ceiling are uninsulated then absolutely add insulation there - foaming? Don’t blow out your sheetrock.

for foaming of pre-existing walls you have to use a different formulation and you go in steps through small holes made from floor to ceiling. youtube it, it’s a routine thing done. keeping the heat out is easier than trying to get rid of it once it is there.

Hi Guys.
Thanks a lot for all of the responses so far, and sorry I haven’t gotten back in here till now.
I won’t go into a lot of detail, but I want to at least respond partially.

Please keep in mind, anytime I reject an offered idea here, I am not really hardcore against it. More likely, this is all still so new to me that I am working it out out-loud. So, please come back after I volley your way and push me on any issue that you think is really important. I will always reconsider at this stage; especially when it seems to be coming from someone with a lot more experience than me…

following with your notated structure…

I totally understand and appreciate your point about simplifying. Any place where it can be simplified (i.e. less config AND less $; because if it’s just less config, it’s irrelevant to me at this point lol ), I’m all for it. However, when it comes to the outside temp, I disagree…but only slightly.
I have actually tested, and the air in this one particular spot (which is partially covered by house structure, but is still outside…and is far enough away from the heat-source inside the house as to not matter for that) is significantly cooler than the otherwise regular, ambient temp of the air outside. So, at the risk of annoying with my OCD, I’m going to stick with the plan of including an outside temp monitor in this particular location (i.e. it is also the place where the air will be taken in from).
Also note… I am already using the weather app, and it fires off warnings when we get a nasty storm in the area, etc. I like it, and it is sometimes much better than the normal weather apps out there for my area. However, it’s just not exactly what I need in this specific situation.

In light of First: above, and the fact that the driveway is a massive heatsink right up to the garage door, I will probably instead try to figure out a safe and efficient way of blocking whatever other holes and/or openings of whatever kind there are on the door to increase the amount of air that comes in through my vent instead of there.

Yep. It does indeed get cold here, and I have already thought of that. It’s just not mentioned in the plan, simply because it’s not really part of the thing I’m most trying to do here. Yes. I will cover the holes appropriately, and I do really appreciate you bringing it up, because it makes total sense to make sure to factor that in when putting this all together.

Good. This is great info to help me along. More questions…
I am assuming that, even if I were somehow magically able to instantly evacuate all of the heated air from the garage and replace it just as instantly with cooler air from outside, it would heat back up again fairly quickly just from all of the heat that has been radiating into and getting soaked up by the structure of the garage itself. With that being the case, would it be better to get a slower moving fan, since a fast fan will end up using way too much electricity by getting the initial job done quickly and then running and running all the time (throughout the established venting period)?

Thanks. Great idea indeed. I have looked around a bit before coming here, but in light of the high cost of one of those kinds of things, I could get a bunch of other things to do this a different way instead, and still have money left over to put toward the next set of gear (whatever it will be) that I will use to do this same thing up in the attic.

This makes sense. So, I guess I will still keep it in mind when it comes time to actually impliment this thing. Most likely, I will still do two temp monitors and only draw air in when it is cooler outside (given the explanation in ‘First:’ above.

Cool air outside at night = yes, indeed. It can be 80 in the afternoon (which means it can be approaching double that in the garage…OK, perhaps exagerating), and then drop at least 20 degrees at night…and so-on.

As for insulation, yes.
As I stated in the OP, I am also planning on insulating the currently uninsullated spots of the garage.
However, this thread on ST forum is only intended to deal with the ventilation project.
I totally agree and appreciate your input as it relates to the insulation, and will come back here to review your comments on that once I get to that project.
NOTE: I know that it would be better to prevent the heat from entering in the first place than trying to get rid of it once it’s there, but since I already have much of what is needed for this project, I’m starting here first.

Up-n-Out: Yep. That’s why that is pretty much exactly how I described it in the OP. Thanks though.
One difficulty in my case is that the highest point in the garage is not directly under roofing…there is a bedroom in the way. So, I won’t be able to go through the roof for the exit vent. Instead, it will need to be on the side of the garage…just as high up as I can get it within the workable space in the garage. It’s not a real problem though, since I’m more concerned about venting the garage than I am about where it goes to once it is outside of the house. As for HOA issues, yes. I will certainly check into all of that. For one of the holse, it is hidden by structure, and won’t matter at all. For the other, it is on a side of the house that is facing the nextdoor house where nobody really ever looks much anyway. So, it probably won’t be an issue, but I will definitely make sure of that prior.

Flamable vapors?
Hmmm…well, I do have a gas can in the garage for the lawn mower, and I suppose some of the lawn chems and other stuff might be such, but the way I see it, there is such a small concentration of that kind of stuff that I can’t imagine it would be problematic in this case. If I blow up my house, I will let you say “I told you so” to my face. lol

Linear air flow:
Yes. I see your point. That is one of the things I asked about in the OP. So, I’m glad you mentioned it.
I think the system I’m going for is more along the lines of
“well, at least with SOMETHING going, I know it will keep it a LOT cooler in here”
“OMG! I have to make absolutely certain that all of the heat gets evacuated immediately”
It seems to me like, if I have even a marginally effective fan going all night, it will serve the purpose at the level I’m going for here.

Shield the sensors:
Indeed. I have considered that as well, and it is a slight part of the reason I’m putting the outside temp monitor under the structure. It won’t completely keep it out of the elements, but it’s pretty close. I think the main thing I will want to do to increase the protection is to install some kind of hood over it to make sure it can totally ‘breathe’, but that it’s not somehow holding heat in the space and messing with the reading.

do not cycle the fan over the internet:
OK. I’m not completely sure if I understand what you mean, but since it sounds like it may be important, could you please give me more detail?

proof of concept:
There is only one opening in the garage to the outside, and it is the large, main garage door.
I have indeed already experimented with leaving the door open, but even slightly lets cats in, and I can’t have that.
Leaving the door open all the way would indeed solve the problem at night in the sense that it would cool it down. However, (besides the part about cats…and/or whatever or whomever else it would let in) it’s heating up all day, and I suspect that, even if I had just a fan going all day and all night without any ‘smartness’ to it at all, it would likely go a long way toward the solution I’m going for. I want to add smartness so that I can monitor it (or, rather, so that IT can monitor it for me so that I don’t need to) and make sure it’s actually functioning properly. e.g. In a situation where I don’t just have it running all day, if a big storm comes up in the middle of the day and cools the outside down, I want to be able to take advantage of that cooling and have the monitors trigger the system to turn the fan on.

Attic heat:
Yep. I totally agree, and as I said in my OP, I will indeed also eventually be working on that.
In my case though, it is so hot up there with no way of managing it even a little, I find it more palatable to start working on this kind of project in an environment in which I at least can open the big door and take advantage of the cooling that is available that way…to have a slightly cooler area to work in while I stumble through and figure things out the first time. Then, once I’ve gone through it once by doing it in the garage and worked out the kinks, I will be more educated, experienced and prepared to do it more quickly up in the attic so that I won’t have to spend quite as much time up in that unrealistically high heat (heat stroke is a very real thing to me).

Insulation a mistake?
I have heard the exact opposite from every ‘smarter-than-me’ person I have ever talked with aboutthis kind of thing.
So, in what way would insulating the garage door and the currently uninsullated portions of the walls and ceiling be a mistake?

[quote=“Robert_Vandervoort, post:5, topic:18108, full:true”]
for foaming of pre-existing walls…[/quote]

Yep. I totally agree.
More details on the garage and how it is and isn’t insulated…
The portion of the garage which is immediately below living space (bedrooms) is already properly insulated. However, since the law doesn’t require it beyond that, they left the portions of the garage that just have roof above them completely bare walls with not even any wallboard, let alone insulation. So, regardless of which kind of insulation I land on (when I eventually get to that project - see notes in replies above), the area to be insulated is clearly marked out, and it should be relatively simple.

Temperature control by sending temperatures to internet, and returning automatic fan commands to your system from internet, is inherently unreliable. You only need a brief reading of these forums to see this will fail often.

Your automatic temperature/ventilation control should be done locally, by a hardwired thermostat, if you care about reliability. Monitoring can done via internet.

I suggested insulate the interior wall and ceiling of the garage.
That’s just what I’ve always seen applied in construction - that insulating unconditioned, unheated space is wrong. If the cold space is tight then you have moisture problems, but that won’t happen in the garage.

oh well good luck.

[quote=“ero4444, post:7, topic:18108, full:true”]
Temperature control by sending temperatures to internet…[/quote]

OK…sorry, but I’m still not understanding either point (and I know the problem is probably in my mind; not yours)…

1. Temp over internet?
I think I generally understand what you’re saying on this one, but still not clearly.
I get the part about how people here have talked about problems with doing it the way you’re describing, but the problem is that, what you’re suggesting is not what I’m talking about.

You’re talking about somehow sending the temp monitor data up to the internet and then back.
However, I’m not. My plan only has the temp monitors here at my house. They will be monitored by the ST hub that is here in my house. Any ‘trigger’ should be handled here in my house.
I don’t understand how the internet gets involved…unless we’re talking about how I could then also monitor it remotely (when away from home), because the ST system allows this with the app, and dashboards, etc.

I sense I must be missing something BIG here (about how ST works). :confused:
If so, please do let me know.

2. Insulate or not?
I’m confused. In one sentence, you said,
“I suggested insulate the interior wall and ceiling of the garage.”

Then, in the same post, you said,
“insulating unconditioned, unheated space is wrong.”

I know it’s probably just me not understanding what you’re saying.
So, would you please explain it another way?

One more try on the nature of the garage in this situation…

The garage is partially insulated. However, they only insulated the portion of the garage which is immediately below living space of the house (bedrooms on the second floor).

So, there are basically three different types of areas that do not have any insulation…

  1. Walls
    There is a wall on the north side and one on the south side. Both of these walls are properly insulated, but only as far out as the upstairs rooms cover the garage. Where those rooms upstairs stops, the insulation (and the sheetrock) stops. So, on both walls, there is an uninsulated (and un-sheetrocked) section of about 4 to 5 feet from there out to the wall that has the garage door on it. Then there is also the portion of the wall with the main door which is the same.

  2. Ceiling
    Most of the ceiling is properly insulated; mainly in that it is immediately below bedrooms on the upstairs floor (i.e., looking at the house from the outside, you can see how there is only a small portion of the garage which actually has roof directly over it, because the majority of the garage is covered by the house above it.
    The section outward from there (outward from the portion covered by second floor rooms) has no insulation or sheetrock.

  3. Main Door
    The main, big garage door is not insulated at all.

I believe @ero4444 is suggesting, but please correct me if I am wrong:

  • The temp sensor in your house sends the information to the hub, which sends it to the cloud (internet), then if the temp is over the limit it sends a command back to the hub to turn on the fan. The components are in your house, but the logic is executed in the cloud. Instead, you should just control the fan with a local thermostat. It is a simple, robust solution and you can simply monitor the temperature via ST.
  • The walls or ceilings that are adjacent to living spaces should be insulated, the others do not need to be due to risk of condensation. If you have your garage well sealed and insulate all of the walls without providing ventilation, you could risk moisture issues inside. Depending on your climate, this is a real possibility.

Thanks. It makes more sense now…

  • Temp
    I guess I didn’t fully understand how ST works.
    Now, that’s strange. Why not have the unit that’s here in my house handle it? It’s like the ST Hub in my house is simply a bridge between the smart devices in my house and the internet, then. Wow. (I assume there is a thread about that somewhere).
    So, if I’m going to do it with a local thermostat, which product lines should I be looking at to handle that part?

  • Insulation
    Interesting. So, since I already expressed that the whole point of this present thread is to design and install some kind of ventilation system in the garage as part of my efforts to mitigate the heating problems in there, does that ventilation system suffice, or do I need something different somehow?

You know, I turned my garage into a kid playroom with 3 skylights and a 8" by 10" sliding doors so do I have heat problem and my initial thought was pretty much like above but instead I installed this Panasonic erv and couldn’t be happier. It’s control by 2 z-wave switches http://www.amazon.com/gp/aw/d/B000XJNZ1Y/ref=mp_s_a_1_50?qid=1436968144&sr=8-50&pi=SL75_QL70&keywords=panasonic+vent+fan

Every major part of this system (other than the air intake hole on the opposite side of the garage. I’m just using the big door cracked open slightly for now until I have time for the hole project) is now in place, and functioning as expected.
When the outside temp is x-degrees lower than the temp in the garage, it turns on the fan.

Since there is so much heat built-up inside the garage, in the walls, the ceiling, the concrete floor, and all of the other objects in the room, it will probably take a few days to really get to the point where I need to be, but even with just the first night of having it in place last night, I can already see the difference it has made…

Normally, in the summer, it is so much hotter inside the garage than outside, that it never inverts by itself (i.e. hotter outside); it builds up so much heat throughout the day with the sun beating on it, and even though that heat then radiates out into the house all night long, it never loses enough of it from the structure of the garage to get to the point of it being hotter outside.

Today, we finally saw the inversion take place… After leaving it run all night last night (taking cooler air through there all night long), I think it really worked on all of that trapped heat in the structure of the garage.

At one point today, the fan turned off. When I checked the devices/temps and the SmartApp, I saw that the outside temp was higher than the temp in the garage (in the summer, this has never happened at any time, day or night, in all the years we’ve lived here; so, substantial confirmation of the general working premise here), and that was why the fan was off. The fan got the heat out, and the SmartApp noticed and turned the fan off. :slight_smile:

The whole reason for doing this in the first place is to hopefully save money on electric bill by reducing the amount of heat that the AC unit has to remove from the house simply because it’s radiating in there from the garage and the attic. I know the heat builds up gradually, day after day, and there is a cumulative effect (terminology=?). Hopefully, it works at least similar in the other direction, and after a few days of extended use, the saved heat will be significantly gone. That way, this new fan doesn’t have to keep running all night, every night. A while of this at the beginning makes sense, but I don’t want to just trade one waste of electricity for another.

The fact that the fan turned off in the middle of the day is a really, really good sign that this is actually working. I just went out into the garage, and I was amazed! Granted, it’s still way hotter than it is in the house, but being cooler in there than the outdoor temp is incredibly encouraging.

1 Like

In the studies we have ran with the solar attic fans we sell it’s proven to cool down attics and garages by 40 degrees! They make a huge difference I am glad you saw results :slight_smile:

If anyone would like to test one for themselves anyone that comes from this forum i will give wholesale pricing to: http://www.magenn.com/product-category/solar-attic-fans/

1 Like

It appears that I am very late to the conversation but I’ll throw in my 2 cents anyways. My house is laid out so that I was able to put the fans in the ceiling of my garage, blowing into my attic. Tried to get two birds with one stone. I started searching for a controller to do this exact thing 3 years ago. At the time I had fans in place but was using a programmable thermostat and guessing at which times the outside temp would be lower. About a year ago I learned of the Arduino. I had already spent 2 years searching for a controller I could buy so I decided to create my own. I took me the rest of that summer and all winter to complete my controller only working on it here and there. It is a self contained unit, no smart phone access but it works well as you have learned. I also added a low limit shut off and a high limit override both adjustable with variable resistors. The low limit is my desired temp. The high limit will run the fan even if it is still warmer outside than inside. My thought there is even though it is hot air, at least the air will be moving. So far it has reached 96 degrees F outside and my garage has only gotten up to 78 degrees F. Seems very good to me considering all I am using is a fan and some logic. Model 2 of my controller is on a solder-less breadboard next to me and currently running. It included more accurate sensor, reads humidity as well as temp, displays the information on a LCD screen, and uses one rotary encoder to adjust the settings as appose to multiple pots. I do enjoy my phone, maybe I will look into how to connect my controller. I would like to help others that are interested in these controllers. If there is interest maybe I could make some diagrams and share my code.

Sounds really cool. Thanks for sharing.
If I didn’t already have SmartThings, I would definitely be doing something like what you did. However, since I do have SmartThings, and since my setup already does everything yours does (and more), I probably won’t be making that leap on this project…at least not in the near-term.

I think, if I had the time, I might actually go for it and put one of your kind together, just for the sake of the experience of it. Seems like having the ST version that I have now could serve as my ‘control’ so I’d know what I’m shooting for in the Arduino version. Oh well…no time. :slight_smile: