Bus Barn thermostatic exhaust fan recommendations?

[Tedsoldbus]

Poured the apron in front of the bus barn today. 6 inches thick with enough rebar and old metal fence posts to keep it from cracking. Hopefully...
Opened the door into the barn today to get ready for the cement trucks and it was mucho caliente in there. Electrician comes next week and the spray foam guys a few days later. The foam should help, but it was only 72 here today with much hotter coming soon. So I'm thinking better run a wire to the far end up near the roof on the far gable end and add a fan after the foam guys come. Lots of wasps and bugs here so thinking something with a louver or flap outside when the fan does not kick on. Any recommendations on brand? Size? 12 or 14 inches big enough? There is some solar stuff on Amazon but since I am about to run wire I am thinking what is one more...

[dtcerrato]

We have two large air movers on one end of the bus barn. Enough cfms to facilitate interior spray painting. One 36" high capacity fan & one 16" square high capacity centrifugal  squirrel cage. Both are louvered. With OH doors at both ends when painting - the opposite OH door is partially open with HVAC air filters in the opening. There's 3T of air conditioning with 4" spray foam roof area & R11 in the side walls. OH doors are 3" foam core. Tames our hot FL summers with high humidity nicely.

[luvrbus]

Restaurant vent fans work good you can mount one vertical or horizonal roof or wall mounted and they are cheap used and they last for ever plus move a lot air 

[dtcerrato]

The units on our bus barn came off of an A&P grocery store we were remodeling into a circuit city. The 3' fan alone move 30,000 CF/min. I guess that goes what you mention of Restaurant (commercial) units. Both are belt driven 1 HP motors mounted vertical in the wall.

[windtrader]

For a rough estimate, calculate the cubic volume of the structure. Then determine how many exchanges you want per hour. Divide by 670 to get CFM and go shopping. If I recollect you are around 1500-2000 ft? At 12 ft height that's a ballpark of 24,000 cf. 15k cfm fan seems pretty decent rate. So many other factors to consider though.

[sledhead]

I have one like this in the back corner of the barn and I installed in infront of a reg. sliding window so in the winter the window is closed to save heat

on the opposite end of the bus barn is a window that I open to get cross flow . it moves a lot of air fast so I installed a switched receptical so I can use a 30 min timer switch at the door to turn it on and walk away and it will turn off in 30 min. or less .

I removed the louvers when I installed it in front of the window

I use it all the time and would not be with out it

https://www.princessauto.com/en/20-in-single-speed-exhaust-fan/product/PA0008979999

[buswarrior]

MUCH bigger than you were thinking.

I might consider running two circuits up there, for a pair of used furnace squirrel cage fans, one, the other or both.

Nobody complains they have too much fan, but they sure do, if there isn't enough...

Run with the big dogs!

Happy coaching!
Buswarrior

[luvrbus]

How tall is the barn as you know hot air rises takes very little movement to move the hot air in tall barns,My building is 18 ft tall for the AZ heat with 2-14ft tall doors my package came wiith roof peak power fan vents I never installed and sold because I get enough air movement through the 14 ft doors on each end plus I didn't want something else to work on 18 ft tall

[oltrunt]

If you think you might spray paint in your shop make sure the fan motor is rated explosion proof.  Atomized paint is easily and explosively ignited and there is generally no redo.  Jack

[Tedsoldbus]

Thanks guys. Not painting after the foam goes on. 26 by 45 by 18 tall. Lake Nottely is at 2000 ft and cooler and drier than Hotalanta but it still gets 85 in July/August.
So Buswarrior - Speaking of big dogs, we just inherited (this morning) a big Black and Tan that I used to walk for the 80 year old neighbors. The old folks recently died about a month apart. We found out the dog was starving because none of the family cared. Going to set her up in the bus barn because she has bitten our dog a couple of times. We are planning a fence around back of the shop with a Mongo sized dog door. Rita is already getting the dog a used sofa. (oh brother). Dog is 9 so it is not a long term thing but can't just let her die. The local shelter won't take her. (Too old and bites other dogs.)
Sorry. I know this is a bus site, but this just stood us on our head. And now I need try to keep the shop even cooler. (unless any of you want a 130 pound Hound) (will deliver)
Not a bad thing. The old Prevost will be happier with a bigger fan unless the tires become big chewy toys.
No A&P around here but advice you have all given me (and now the orphan dog) has me re thinking a bigger unit. I am getting 200 amp service in 2 weeks so I should be able to power anything.
I will do more homework now that I have advice and ideas from my BCM friends.
Thanks guys

[chessie4905]

I have a 48" fan with  louvers mounted horizontal to ceiling. Haven't opened coupula for full outside vent. Currently run it in spring and fall to push warm attic attic air down steps to warm up the shop without using furnace. I keep shop mostly closed in hot summer which keeps it in the 70's, due to overinsulated and concrete floor. Shop stays just above freezing in winter time with no heat. You just can't  beat extra insulation.

[Tedsoldbus]

I have a 6 inch slab and planning 3" foam on ceiling and 1 1/2 on walls (recommended by foam guys for our climate). I hope that makes a huge difference in how hot it was a few days ago. It surprised me a bit, but right now it is just a big hunk of metal. I toyed with a copula but hope the fan works. How does air get in? Enough gap around the 14 foot and 6 by 8 rollup doors? It has to come in somewhere if I push 48 inches of air out. If not enough air from around the roll up doors maybe open the screened window that is never in the sun??
It is getting exciting. Power service will come into the building right next to the bay my 50 amp cord comes out of. Very short run for the cord so less tripping hazard. A friend just gave me an 8 foot hunk of corrugated metal pipe (not sure what it was used for??) that just fits on my exhaust pipe. I can put it on the tailpipe and fire up the 6V92 and have all the fumes go out the door of the the bus barn (and now, worlds largest dog house) until it airs up enough to back out of the barn.
Ga Governor just signed a bill that cancels the gas and fuel state tax for a few months to help with rising costs. That is 38 cents a gallon on gas! Not sure what it will be on Diesel but I will run to fill the bus when that hits. (The bus is still on 1/4 tank after the Florida trip.) If you live near the Ga border, keep an eye on that. News says the price drop should go into effect after the fuel that was already purchased runs out. We are already 30 cents cheaper than Florida, and I need about 180 gallons....

[chessie4905]

I have two foot overhang on sides with full ventilation along with ridge vent. I like the 48" as pulleys and vbelt keeps speed low for quiet ventilation. I also have one 48" in a box on casters to provide air when working in the heat. Have the speed low enough so it doesn't try to roll away.

[luvrbus]

I have a 6 inch slab and planning 3" foam on ceiling and 1 1/2 on walls (recommended by foam guys for our climate). I hope that makes a huge difference in how hot it was a few days ago. It surprised me a bit, but right now it is just a big hunk of metal. I toyed with a copula but hope the fan works. How does air get in? Enough gap around the 14 foot and 6 by 8 rollup doors? It has to come in somewhere if I push 48 inches of air out. If not enough air from around the roll up doors maybe open the screened window that is never in the sun??
It is getting exciting. Power service will come into the building right next to the bay my 50 amp cord comes out of. Very short run for the cord so less tripping hazard. A friend just gave me an 8 foot hunk of corrugated metal pipe (not sure what it was used for??) that just fits on my exhaust pipe. I can put it on the tailpipe and fire up the 6V92 and have all the fumes go out the door of the the bus barn (and now, worlds largest dog house) until it airs up enough to back out of the barn.
Ga Governor just signed a bill that cancels the gas and fuel state tax for a few months to help with rising costs. That is 38 cents a gallon on gas! Not sure what it will be on Diesel but I will run to fill the bus when that hits. (The bus is still on 1/4 tank after the Florida trip.) If you live near the Ga border, keep an eye on that. News says the price drop should go into effect after the fuel that was already purchased runs out. We are already 30 cents cheaper than Florida, and I need about 180 gallons....

You are joking about the 8ft wide doors I hope 

[RJ]

Ted -

Is this what you're thinking of? HD has a wide selection, I just picked this one as an example:

https://www.homedepot.com/p/20-in-Silver-3368-CFM-High-Speed-Shutter-Exhaust-Fan-DHS-YDHF-AUST20/319713405

They've got models that are lower CFM numbers and well as higher capacity. They even have some two-speed units, which might fit the bill, too.

As Clifford said, I, too, am hoping you were joking about you roll-up doors only being 8' wide!

Ten minimum, 12 x 14 preferred! 12x16 even better!

FWIW & HTH. . .

RJ