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DrBoost MegaDork
6/8/22 4:15 p.m.

In October I moved to Florida from Michigan. Nobody bothered to tell me it gets hot and humid down here wink Nope, none of my friends warned me LOL.  Anyway, I want to cool my garage on the cheap. On the cheap means no A/C. Not so much because I don't want to pay for a split system, but because I don't want to run the A/C 24 hours a day for 285 days a year when I'm not in it THAT much, really.  

So I have a question, and an idea that comes with it, another question.  

If I'm not going to condition the space (20 X 30 metal building), is there really a point in insulating it? It's a light-colored building that is partially shaded from the west and south. 

That's the question. The idea is installing a solar-powered gable fan to extract heat. Here's my idea. Get a radiator fan from the junk yard and a solar panel. When the sun is out, the fan is running. Seems simple enough. But, if I have the fan wired right to the solar panel, will I burn the motor out when the panel is putting out something less than, say 11V? 
If so, is there a switch I can put inline that will stay closed until voltage is at 11.5V or something?  

Am I over thinking this? Am I under thinking this?

hobiercr UltraDork
6/8/22 4:18 p.m.
hobiercr UltraDork
6/8/22 4:23 p.m.

Also in FL, but slightly N of you. I bought and installed two of THESE FANS in my uninsulated shop a few years ago. I had originally thought to put them on a thermal switch but ended up just using toggle switches. When I walk into the shop they go on as well as an "in" box fan on a window. I add fans as necessary depending on the day.

It's still hot.

The long term goal is to insulate, add a ceiling, and AC. Even if I keep it at 82 it will pull the humidity out.

drsmooth HalfDork
6/8/22 4:24 p.m.

I know A/C isnt your goal but... This thing runs off solar all day, and grid power at night. Plus it has a heat pump, not that you will likely need that. 



Tom Suddard
Tom Suddard Director of Marketing & Digital Assets
6/8/22 4:30 p.m.

This isn't what you want to hear, but just insulate it and add A/C. My insulated 24x30 just has a big window unit in the wall, and it's plenty. On the hottest summer days it will only drop the interior temperature down to about 80 degrees, but it still pulls the humidity out and it's perfectly comfortable to work in. On normal days it will cool it down to the mid-70s. When I'm not in the garage, I just set it to 82 degrees and it still keeps the humidity down and keeps the cars/tools in better shape. This seems to cost me $10-$20/month on my electric bill. 

If you're committed to skipping A/C, I also put a big exhaust fan in the wall opposite my window. It's great for venting fumes and makes a nice breeze, but I find myself flipping the A/C on once it hits 80 degrees outside. 


pres589 (djronnebaum)
pres589 (djronnebaum) UltimaDork
6/8/22 4:47 p.m.

I'm wondering about roof mounted solar cells acting as a bit of a sun load reducer which, by themselves, would reduce temperatures a bit in your garage.  This is actually something I want to do in my own garage and see as a nice side benefit.  

Agreed with previous mentions of running an A/C unit with the temperature set to something in the low-80's to keep the temps relatively comfortable and humidity down.  Having some solar power to make up for some of the energy consumption seems like a win/win.

Pete Gossett (Forum Supporter)
Pete Gossett (Forum Supporter) MegaDork
6/8/22 5:40 p.m.

I have a 4'x6' door opposite my 2 garage doors. If there's a nice breeze it can be tolerable in the summer. I imagine one of those large fans on wheels would help pull the air through when there's no breeze, but I don't have anyplace out of the way to store one. 

I guess my point is that just moving hotter air out & cooler air in isn't really going to help much. You need to be standing directly in the airflow if you don't want to have a heat stroke. Or insulate & install a/c - that's on my long-term to-do list. 

logdog (Forum Supporter)
logdog (Forum Supporter) UberDork
6/8/22 5:45 p.m.

Swamp cooler filled with Faygo.

M2Pilot Dork
6/8/22 6:23 p.m.

In reply to logdog (Forum Supporter) :

Probably won't have much luck with a swamp cooler with FL humidity.  But the Faygo sounds good.

DrBoost MegaDork
6/8/22 6:59 p.m.

Interesting about the A/C only costing 20-30 a month. Judging by the rust I've seen on some of my tools, the 20-30 a month could be saving some expensive tools. 
logdog, I come in from the shop all sweaty and sticky already. I can't imagine standing in a mist of Faygo Rock and Rye. 
But if you swing down this way, we can make that happen sweet cheeks. 
Tommy and Hobiercr, how much qnd what type of insulation do you have?  
Oh, that article that was linked is what got my mind thinking about this. 

Lof8 - Andy
Lof8 - Andy SuperDork
6/8/22 7:22 p.m.

I have a 1500 sf metal building shop in FL. The only insulation I have is the thin reflective bubble stuff the building manufacturer offered on the ceiling. The first year, I used a couple big fans to create circulation. It was still a sweat shop in the summer. Last year, I added a 3 ton mini split. If I turn it on 30 minutes before I start working, it's cool and comfortable by the time I get in there. It works amazingly and I haven't noticed any significant difference in my electric bill. I'm out there 3-6 times a week. I highly recommend a mini split!  Cools like a mofo!

Tom Suddard
Tom Suddard Director of Marketing & Digital Assets
6/8/22 7:22 p.m.

I have whatever standard fiberglass insulation fits in 2x6 studs and 2x4 rafters. Nothing crazy. And my doors aren't insulated.

I did insulate every single stud space and the ceiling, though. 

David S. Wallens
David S. Wallens Editorial Director
6/8/22 7:48 p.m.

My dad did a minis-split in their garage and seems happy with it.

Toyman! MegaDork
6/8/22 8:10 p.m.

I'm a little north of you in South Carolina. But I am on the coast and humidity we have in quantity.

Install the A/C. It will be worth whatever the cost. 

Summer months, from mid-May until mid-September, I run a 5000 BTU window unit set to about 80. It doesn't do much for cooling but it does keep the humidity under control and keeps my machine tools from turning into piles of surface rust. It adds about $25 to the shop's electric bill. It's worth it to me to keep the tools from going to E36 M3. 

I also have a 2-ton mini-split. If I'm going to be working out there in the heat, I turn it on about 30 minutes before I head out to the shop. It is very oversized for a 26 x 26 shop so it doesn't take long to cool things down. 


JThw8 UltimaDork
6/8/22 8:56 p.m.

I had my 30x50 put up last year (North Carolina) only insulated the ceiling.  To your question about insulation being worth it, yes it would be.  You can feel the heat radiating off the walls.  However Im cheap and have better ways to spend my money so I deal with it.   

My only cooling is the 2 roll up doors and I installed 2 36" oscillating fans.   I spent the last 2 days out there in high 80s low 90s temps and it was livable.

No photo description available.

Slippery PowerDork
6/8/22 9:06 p.m.

South of you ... biggest news is that its not really hot yet, wait until August/September. 

I did a 1.5 ton Mini Split for ~$1k and it cools my 700sqft just fine. I set it to 80 when I am not there and to 70 when I work in it during weekends. $30 tops. 

I bought it from Costco and diy'ed it. Mr Cool. There is a thread here somewhere I did. 

Slippery PowerDork
6/8/22 9:08 p.m.
DrBoost MegaDork
6/9/22 8:54 a.m.

In reply to Slippery :

Thanks for the link.  

Where are you? There's not much south of me until you get to Miami.

CrustyRedXpress HalfDork
6/9/22 9:10 a.m.

In reply to DrBoost :

I'm a couple hours south of Tampa and finally put a window unit in my 1.5 car garage-it just wasn't possible to work out there for any length of time without it. 

Solar is great (it powers 100% of my house) but since you are looking for cooling I'd also consider planting some trees for more shade-the temps under the live oak in my yard are much, much lower during the summer. 


DrBoost MegaDork
6/9/22 9:17 a.m.

In reply to CrustyRedXpress :

I've thought about that. I'll post an overhead pic shortly of the lot. 
Interesting thing. I was reading about palm trees and learned that the vast majority of palm trees in FL are not native to FL. The state has an initiative to limit the number of new palms planted, I think something like 25%. They basically do nothing to keep surface temps down, and next to nothing to reduce green house gases.

DrBoost MegaDork
6/9/22 10:01 a.m.

I really want to avoid A/C, but I don't think I can do that. I like the diy mini split though. 
Here's my shop. As you can see, it's maybe 10' from the fence on the west side. There are trees, but no significant shade until the sun is low enough to not make much of a difference, if any. I do like the idea of tree cover, but I'm afraid I'll be worm food by the time a tree I've planted is tall enough. I've thought about putting a trellis up on the west side and putting a vine of some sort, not sure if that's a good idea though.  

Looking west



John Welsh
John Welsh Mod Squad
6/9/22 10:21 a.m.

Door faces east so the door starts heating up early as the sun rises.  I would get that door insulated.  That can be pink foam board cut to fit and glued on the inside (if it's not already insulated.)  

Are you working (desk work) in the whole space?  I would recommend in the NW corner adding two insulated walls on the inside to make a 10x10 work room.  Then add a window and a window unit AC to make it bearable.  



SkinnyG (Forum Supporter)
SkinnyG (Forum Supporter) PowerDork
6/9/22 10:27 a.m.

Absolutely insulate it, and insulate it well. 

Use a good quality vapor barrier. Keeps the heat out and the cold out.

I have no A/C in my shop, but at 98°F outside, it still stays under 70°F in the shop (as long as I don't open the roll-up door and let all the heat in).

2x6 construction, fully insulated, the only windows face north.  The thickest (highest R-value) roll up door I could order.

Then again, due to the slope of my property, the doors are on grade but the back is 3' in the ground which helps.

Ian F (Forum Supporter)
Ian F (Forum Supporter) MegaDork
6/9/22 11:06 a.m.

I agree with insulating any of the walls facing the sun. My ex's garage faces the west and the two original wood garage doors would turn into giant radiators. Replacing them with metal surface insulated doors made a big difference. As we started to insulate and cover the walls, we definitely noticed a difference in radiated heat standing next to insulated wall sections and bare stud wall sections.   We rarely fitted a window unit bigger than 10K BTU, but while it didn't do much to cool the 28x24 x10 space, it did cut some of the humidity which made working inside more tolerable.

Slippery PowerDork
6/9/22 11:14 a.m.
DrBoost said:

In reply to Slippery :

Thanks for the link.  

Where are you? There's not much south of me until you get to Miami.

West Palm Beach. 

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