Air Conditioning Sizing?

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Forum topic by spanky46 posted 06-21-2009 04:36 PM 3635 views 0 times favorited 7 replies Add to Favorites Watch
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995 posts in 2810 days

06-21-2009 04:36 PM

Topic tags/keywords: question air conditioning sizing cooling

My former garage and now workshop is 24’ by 24’ by an average height of 9.5 ’. Taking out for cabinets and equipment (see workshop my site) I need to know the approximate size wall mounted AC required. The shop is insulated and has one 16’by 7’ garage door, one 3.0 outside door and 2- 48” by 48” insulated windows.
It has a sloped concrete floor.
Any information would be greatly appreciated! Trying to find something used!

-- spanky46 -- Never enough clamps...Never enough tools...Never enough time.

7 replies so far

View Craftsman on the lake's profile

Craftsman on the lake

2506 posts in 2858 days

#1 posted 06-21-2009 04:42 PM

Hmm…. I’d say anything about or over 10,000 btu would be more than enough. An 8000 would work well too but probably run longer. I doubt that 6000 which is like a bedroom ac unit would keep up. It all depends on your outside temp. If you’re in the south then bigger. If in the north just dealing with the summer then smaller.

And I’m no AC expert. It’s just that I have a 24×24 insulated shop too. Mine is 16000 btu. It’s way overkill but it was given to me as a used unit. I never would have sprung for one that size if I had bought it new. I don’t have a garage door though so can’t speak for how that would be.

-- The smell of wood, coffee in the cup, the wife let's me do my thing, the lake is peaceful.

View Maynard's profile


36 posts in 2724 days

#2 posted 06-21-2009 04:45 PM

Take the square footage of your shop to a local appliance store and determine from them the size of your unit that is suitable for your climate.
Then you can buy one used that is that size.

View cabinetmaster's profile


10874 posts in 2978 days

#3 posted 06-21-2009 04:47 PM

Where are you mounting this unit? I’d go look at Lowes or Home Depot. They usually go by the size of the room. Yours is 24×24 or 576 square feet. I’d see what they reommend in BTU’s for that size room and get the next size bigger. I bought one and mounted it in my window. It was rated for the size of the room and justs gets by. I wish I had bought the next size bigger.

-- Jerry--A man can never have enough tools or clamps

View spanky46's profile


995 posts in 2810 days

#4 posted 06-21-2009 04:56 PM

Cabinetmaster, I will be mounting it in a wall with a southern exposure but there is a 3 foot overhang and lots of shade!

-- spanky46 -- Never enough clamps...Never enough tools...Never enough time.

View BTKS's profile


1984 posts in 2884 days

#5 posted 06-21-2009 08:02 PM

Go with recommended size for climate or ONLY ONE size bigger. Too big and it will not run long enough to dehumidify. Most of the advantage to AC is the drop in humidity and comfort factor, not necessarily to temp.
Bigger is not always better. Been through that scenario with a small house. 24,000 BTU too big, 18,000 just right. Good luck

-- "Man's ingenuity has outrun his intelligence" (Joseph Wood Krutch)

View CharlieM1958's profile


16229 posts in 3638 days

#6 posted 06-21-2009 11:57 PM

BTKS is right. The last thing you want is a unit that is too big for the space. As he said, it will short-cycle, leaving too much humidity in the room. Not only is this a comfort issue, but you could easily wind up with condensation on your metal tools and surfaces… not a good thing.

-- Charlie M. "Woodworking - patience = firewood"

View MedicKen's profile


1610 posts in 2882 days

#7 posted 06-22-2009 12:57 AM

I have a standard 2 car garage that has been insulated in all walls and the ceiling. R19 in the walls and R30 in the ceiling. I have a 10,000btu window unit that I installed in the mandoor, cut a hole and made a support shelf/bracket. It does a fairly decent job of keeping it tolerable. In my climate, avg summer temp of about 95, with an easterly exposure to an insulated metal garage door, inside temps range in the low 80’s.

-- My job is to give my kids things to discuss with their

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