This week I should be signing the lease on a modest shop that will be shared by my business partner and me. I'll finally have some space to finish my car.

The shop is 30x24 with a 9.5x11.5 office with a 5,000 BTU AC unit which we will use as a shop room to house the compressor, bead blaster, drill press, and that sort of thing.

My real question is does anybody have any experience sizing a room air conditioner for such a shop?

I know the proper calculation is not btu/sqft, but I'm not going to calculate heat gain and all that other stuff. I've found a few calculators on-line and come up with anywhere from 12,000 btu to 20,000 btu with modifiers for amount of insulation and tall ceilings. The shop is open to the roof but has an insulated roof. The wall height is about 12' with about another 6' to the peak. We're going to lightly insualte the metal walls with R3 or R4 foam board, mainly to keep the walls from radiating the heat.

My best guess is we'd want 18,000-22,000 btu given the height and the light insulation. But, this group is diverse and there may be someone here who can give me an informed opinion from experience and/or training.

So, anybody have a recommendation? I know it's as bad to go too big as too small.

 

Alright Geo! Congrats! I have no idea on what would make a "correct size" unit. Does seem to me that the lack of interior walls, low R value, and the high ceilings will ensure that no matter what size unit you get, it isn't going to be enough when the humidity is 95% and the temp matches. I guess it's possible to go to big, but I'd be far more worried about going to small. What part of town is the new shop in?

 

Thanks Keith! It's on the east side off highway 90. It's literally 5 minutes from my office. I found it totally by accident when I took a wrong turn accidentally on my way home from work last week.

I too am concerned about high temps, high humidity, little to no insulation, and high ceilings. Believe it or not, it absolutely IS possible to go too big. What happens when you go too big is that the unit doesn't run long enough to take the moisture out of the air and it feels clammy. I was originally thinking we'd need a 24k btu unit. After some discussions on the racing forum and some on-line research, I'm thinking 15-18k btus.

Here are a couple of photos.....

 

Here's an inside shot.....

 

Another inside shot....

I'm going to try to meet with the owner tomorrow. I hope to have papers signed by the end of the week. The only thing that would squash the deal is not allowing us to change out the rear door to install the AC unit. I simply MUST have an air conditioned shop.

 

I agree now that I've seen the photos. It would not be that hard to over crank the AC. For some reason I was thinking the building was larger - just didn't read your post close enough. Actually, I'm pretty sleepy so I doubt if I'm reading anything correct - least not the first time. BUT - an a major but it is - that looks to be just about the perfect size for your "operation". As you know, if the AC is too large then the unit will not cycle long enough to remove the humidity from the air and you'll never get it as cool as you'd like. My original comments about not being able to go "too big" were based on my dozing off while I type and daydreaming of Jay Leno's garage...