Cooling a 26x36 shop

[otherguy]

I have a large metal pole barn and part of the barn was walled off and that part is the shop part and is approx. 26x36 with two 10' wide roll up doors and concrete floor, two windows in one wall. It's probably 14' eaves and 18'-20' at the ridge.

So one shop wall separates the shop and barn so is not exposed.
Another wall is protected by a lean-to that runs across the back of the barn.

I am in Missouri, so hot and humid during parts of summer.
Would a window unit work or should I look at more something like a MrCool?

Before answering, know these things:
• The entire shop part is spray foamed with 1.5-2" of foam, walls and ceiling.
• I don't get to work in the shop all the time, sometimes only every other weekend.
• I don't really want it to be super cool in there, just take some of the heat and humidity out, even if that just means getting around 80 degrees, that should be fine for me and the tools/equipment (woodworking).
• Would like to just run it a few hours before I go in there if possible.

I am really just want to make it a bit more comfortable so I can work out there more.

Just wasn't sure if a window unit would do that or I needed a MrCool?
Thanks for any suggestions.

 

[Jackfre]

You will have much greater comfort and economy with a mini-split. I think a 24 would be about right. I think your biggest problem is dehumidification. I do not know if a Mr Cool has a "dry" mode on its control but it is a really nice feature, costs very little to operate and you and your tools are much happier. By hitting that latent heat first it is much easier to cool when you want it.

 

[theoldwizard1]

Add additional insulation, especially in the ceiling.

26x36 is at the point where 2 air handler could make a big difference. "Dry" (dehumidify only) is nice.

 

[ticklechicken]

I have a very similar setup to you

• 24 x 45 shop
• 2" closed cell on walls
• 3" closed cell on ceiling
• 10' eaves
• 13' peak
• Florida heat and humidity

I went with two separate 18k mini splits. I can achieve what you're looking for by only running one of them. With two of them running, I can easily get it to 68° in the shop on the hottest of days.

My original goals were the same as yours - to just get it comfortable and keep rust off my woodworking tools. My shop is on its own meter, and I learned after a few months that these mini splits cost nothing to run. I now keep the shop at 80° all the time, and set it to 70° when I'm working. The highest bill I've seen is $17.

Window units would have reduced the initial purchase cost, but that would have dwindled away every month. Mostly, I would never feel at ease spending the money to get my shop as cool as I like it.

 

[mike93lx]

Do you have an opening that you could slide a window unit into? Even if it just pointed into the rest of the barn.

If so, give it a try. Might be enough.

For a mini split, 2 tons is a lot for that space. I bet a Calc would tell you 12k or less. Too much a/c isn't good

 

[otherguy]

I have a very similar setup to you

• 24 x 45 shop
• 2" closed cell on walls
• 3" closed cell on ceiling
• 10' eaves
• 13' peak
• Florida heat and humidity

I went with two separate 18k mini splits. I can achieve what you're looking for by only running one of them. With two of them running, I can easily get it to 68° in the shop on the hottest of days.

My original goals were the same as yours - to just get it comfortable and keep rust off my woodworking tools. My shop is on its own meter, and I learned after a few months that these mini splits cost nothing to run. I now keep the shop at 80° all the time, and set it to 70° when I'm working. The highest bill I've seen is $17.

Window units would have reduced the initial purchase cost, but that would have dwindled away every month. Mostly, I would never feel at ease spending the money to get my shop as cool as I like it.

That's good to hear, I really only want to do one of them at least for now, maybe in a year or two I could see if another one was needed. I agree, that window units are cheaper but over the long run, maybe even using it more than I think it would, cost more overall.

How high above the floor are your Units?

 

[930dreamer]

A mini split and a ceiling fan?

 

[Rusty Fords]

Read the installation instructions they will tell you the recommend height. To high the unit will not work right in a big are.

 

[Donzi camino]

My garage is 22x35 and I put a 24 mini split and it keeps up just fine. Its Super quite ,has heat and runs pretty efficiently. I like to have my doors open so I really hardly use the ac that much unless its blistering heat and plan to work in it for the day. So the point is that the way I use my ac I would have been better of with thru wall type window unit. I find if I keep ac unit on I don't want to open big doors cause I spent so much time and money getting to that temp that goes away so quick! So for just a blast of ac now and then, I say get thru wall unit.

 

[yeldogt]

I have a very similar setup to you

• 24 x 45 shop
• 2" closed cell on walls
• 3" closed cell on ceiling
• 10' eaves
• 13' peak
• Florida heat and humidity

I went with two separate 18k mini splits. I can achieve what you're looking for by only running one of them. With two of them running, I can easily get it to 68° in the shop on the hottest of days.

My original goals were the same as yours - to just get it comfortable and keep rust off my woodworking tools. My shop is on its own meter, and I learned after a few months that these mini splits cost nothing to run. I now keep the shop at 80° all the time, and set it to 70° when I'm working. The highest bill I've seen is $17.

Window units would have reduced the initial purchase cost, but that would have dwindled away every month. Mostly, I would never feel at ease spending the money to get my shop as cool as I like it.

When I'm doing my heat/ cool loads I have no problem if I'm up in the 1100sf per ton w/ spray foam. You basically have 50% above that with only one unit. The key as you have found is maintaining a temp. In doing so you are keeping humidity in check ... this is the real killer with AC recovery. Let the humidity rise and the amount of energy to remove that water causes massive oversizing.

 

[yeldogt]

Add additional insulation, especially in the ceiling.

26x36 is at the point where 2 air handler could make a big difference. "Dry" (dehumidify only) is nice.

With correct insulation --- In a large open space a single point AC used to maintain humidity levels works very well. It's why you can do a well insulated two story open house with only two heads.


leaking windows or doors ... or large solar gain needs to be overcome. That's a different situation. You can't have a drafty door on one side of a space and do a load calculation w/o taking that into consideration. Same with a lot of windows and solar gain .... you need a point to overcome that directly.

In many shops with good insulation and normal windows ... one head is fine. I do 1600 sf

 

[ticklechicken]

That's good to hear, I really only want to do one of them at least for now, maybe in a year or two I could see if another one was needed. I agree, that window units are cheaper but over the long run, maybe even using it more than I think it would, cost more overall.

How high above the floor are your Units?

The bottom of my units are 8'2" above the floor. Here is an old pic I took during the install.

When I'm doing my heat/ cool loads I have no problem if I'm up in the 1100sf per ton w/ spray foam. You basically have 50% above that with only one unit. The key as you have found is maintaining a temp. In doing so you are keeping humidity in check ... this is the real killer with AC recovery. Let the humidity rise and the amount of energy to remove that water causes massive oversizing.

I highlighted your last point, because I've found that to be very true. After I bring a vehicle into the shop, it takes a surprisingly long time to cool everything down. With 36k, it takes 6-12 hours to recover. If I had a single 12k unit per the load calc recommendation, it would take three times longer. I would not have been happy with those results.

 

[nadogail]

Thanks for the update.

 

[Briguy_123]

With your infrequent use i wouldn't think the cost and complexity of one or multiple mini splits would be feasable. A 24k btu window unit through the wall would make your shop pretty comfortable for 5 or 600$. I cool my 34x48x13 with one. Its 90 degrees here, I ran it for about 3 hours today and my shop is around 65 degrees. I maintain the humidity year round with a large dehumidifier. So it isn't clammy either. Free advice take it for what it's worth.

 

[ticklechicken]

With your infrequent use i wouldn't think the cost and complexity of one or multiple mini splits would be feasable. A 24k btu window unit through the wall would make your shop pretty comfortable for 5 or 600$. I cool my 34x48x13 with one. Its 90 degrees here, I ran it for about 3 hours today and my shop is around 65 degrees. I maintain the humidity year round with a large dehumidifier. So it isn't clammy either. Free advice take it for what it's worth.

The place I bought my pioneer units from sells 24k mini splits for $1k delivered. I did the installation myself. Even if you ignore the monthly cost savings, I'd still spend the extra just for the quiet operation.

 

[Briguy_123]

I understand the versatility of these types of these units. For instance adding cooling in masonry buildings with hydronic heat etc. They are just a not my favorite choice in a shop, especially if their is room for some simple ductwork and a split system with a real filter. 1k is a heck of a price for a mini split delivered.