AC in Garage

[Deere Dude]

I added an attached garage to my house approx 27x40 average with 9' and 10' ceilings. One part drops down a little bit. Approx 1100 sq. ft.

It is getting rather warm and sticky in the garage and I want to put a wall mounted AC in. We have a food processing area in a third of it with sink and stove and cabinets. It also has file cabinets with paper products in it.

It has a wire in the vicinity already.

The ceiling has about a foot of fiberglass and 6" in the walls. The 2 garage doors are 2" steel insulated type; 9x7 and 8x10. Two steel man doors and two 3x3 windows. It does stay fairly cool compared to the hot humid days even without AC, just wanted a little more.

What would be a fair BTU needed to dehumidify and cool it a little bit. I don't want a dehumidifier because that won't cool anything.

I am thinking 15,000 to 18,000 BTU but am looking for an experienced guess.

I understand that a smaller unit running longer will dehumidify better than a bigger unit running less.

Just looking for a wild guess. Thanks.

 

[JPRambo]

the guys at work say 12000 BTU per 400 sq ft

 

[kenmac]

Without seeing it Just a wild guess would be 24,000 BTU

 

[newbury]

Can you give us some idea of your budget, skills and usage?

For example my budget for my workshops in Mississippi is MINIMIZE. I finally put a second hand 10K window unit mounted through the wall to cool down an area about 15x30x8 that is an "apartment" on the end of one shop. Net cost, other than tin snips etc to cut the hole, about $5 for spray foam.

I'm presently having an addition built on a house in Virginia of about 1,000 sq feet and we will be adding 2 split units totaling about 20K BTU. Cost a lot more. Total contract out.

/edit
Your need for cooling capacity can be heavily dependent on your wallet. I can put up with a 10K window unit that cools my shop apartment to 80 degrees and I installed myself.

Others need their area cooled to 72 degrees. If I tried to do that in my shop apartment I'd probably need 20K BTU.

 

[dadster4]

If you will be leaving the AC on most of the time 18,000 BTU will get you by, but if you will be turning it on and off a lot with weather conditions, I would step up to a 2 ton unit.

 

[George2615]

I have a 24x24x14H garage and an attached 18x32x10H garage on back. The back garage connects by a 12' W x 7' H opening. Each is 576 sq ft. (1152 sq ft total).
I use a window A/C unit mounted in the wall of each garage.
The front garage has 3 1/2" insulation. The A/C unit is a 220V Trane unit 14,500 BTU.
The rear garage has 6" insulation and uses a 120V unit of 12,500 BTU.
As long as the doors stay closed they will keep my garage around 70* when its 85* outside.
I'd suggest installing 2 A/C's, One on each end of your 40' garage instead of just one unit.

 

[Deere Dude]

Can you give us some idea of your budget, skills and usage?

For example my budget for my workshops in Mississippi is MINIMIZE. I finally put a second hand 10K window unit mounted through the wall to cool down an area about 15x30x8 that is an "apartment" on the end of one shop. Net cost, other than tin snips etc to cut the hole, about $5 for spray foam.

I'm presently having an addition built on a house in Virginia of about 1,000 sq feet and we will be adding 2 split units totaling about 20K BTU. Cost a lot more. Total contract out.

/edit
Your need for cooling capacity can be heavily dependent on your wallet. I can put up with a 10K window unit that cools my shop apartment to 80 degrees and I installed myself.

Others need their area cooled to 72 degrees. If I tried to do that in my shop apartment I'd probably need 20K BTU.

The budget is whatever it takes. I was looking at ACs at Lowes today starting from 10,000 BTUs to 24,000 BTU from $3-500 which seemed alright. Anything would be fine as long as it is not to small that it runs all the time or to big that it is on an off in 5 minutes. It is for keeping the temp 75 deg and the humidity down somewhat.

I don't think I would have a problem putting it in, but framing it would be the hardest part. Redoing the siding would be the worst part.

I didn't think of a split unit. I'll have to check that option out. Good idea.

For usage it would run a few weeks ago until maybe September. The electricity is reasonable here, right now.

 

[bamboozled]

I bought a window unit for my garage a couple years ago, haven't put it in the last two summers but put it in last week when it was 95.

Anyhow, my garage is about 27x27x9'6", insulated, insulated two-car door and based on what I remember paying for the unit its probably a 10K unit. It has no problem keeping my garage as cold as I want it to be. Love it, so nice to be able to work out there and be comfortable.

 

[Redneck in training]

Mini splits work great and are very efficient but cost several times more than window units. You have to hire a certified installer to keep warranty. I have one in my shop cooling only guest room and my office. I think it is 14000 BTU. It cost around 2500 installed. It is a heat pump because we need heat in the winter.

 

[dragoneggs]

Funny... this is a geographic thing. I want heat in my shop. A/C is never a consideration. I imagine your humidity is plenty but what about a swamp cooler. Way out of my league here. Just :stirthepot:

 

[George2615]

Funny... this is a geographic thing. I want heat in my shop. A/C is never a consideration. I imagine your humidity is plenty but what about a swamp cooler. Way out of my league here. Just :stirthepot:

The OP didn't ask about heat, just A/C and I spend time in my garage in cooler weather also. I heat mine using a mobile home furnace. Also have radio and TV. Can't justify adding a bathroom or I'd probably live out there.

 

[Deere Dude]

Yes, heat is fine already. The coldest it got in the garage all winter was 48 deg in the center.

For me the heat and humidity in the summer are a concern. It takes a while to get hot inside the garage because of the insulation, but it gets in the low 90s if I remember.

 

[kenmac]

well, A/C is really doing the Dehumidifying for ya.. Do a heat gain calculation .. It should get you close to what you need for cooling. here's 1 that may help you.. it should give you some idea..
Don't forget.. people (like a lot of things) give off heat

Free Air Conditioning Calculator

 

[Deere Dude]

I ran the AC calculator above and it shows 18,000 BTU. From everones comments and my own educated guess I guessed either 15k or 18k. Thanks folks.

 

[dodge man]

Run a dehumidifier anyway. It will make your AC unit more efficent. All that water dripping off the coils is steeling some of the cold. I run a dehumiifiier in my garage all the time, it keeps all my tools from rusting. It can get pretty sticky without it.

 

[TractorGuy]

I would put a 3 or 3.5 ton package unit on the outside and duct it in.

 

[grnspot110]

Just for comparison's sake, I had a 9,000 btu mini split put in my new 14 x 20' shop for $1500 this spring. This is for heat & air both, quiet & supposed to be very efficient. I've been running it at 73* the last week with 95-100* weather outside, turning it on about 7 am & off around 4 pm.