# Shop air conditioning



## tbaker1350 (Jan 16, 2015)

Hello all,

I live in north MS and the heat in my shop is getting pretty severe. My "shop" is my 2 car garage, roughly 20'x20' with no windows. The exterior walls are brick and I'm sure the walls aren't insulated. Above the garage is a bonus room which may or may not be insulated between the garage ceiling and floor space. I have tried using multiple fans and even making one of the homemade AC units seen on youtube with no relief. 

I am considering purchasing a portable AC unit. My thoughts are to go with a slightly oversized (14k BTU) unit to account for the uninsulated walls and garage door. I was wondering if anyone had any experience with one of these units, especially in a wood working environment. Seems to me the dust levels could be a major factor in how well these units work.

Thanks for the input.


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## MT Stringer (Jul 21, 2009)

I have a11K BTU split system AC in my garage. We insulated the outside wall when the siding was replaced. 11 inches of blown insulation in the ceiling (R38). Energy efficient garage door (single car garage).

94 outside, 74 inside. :thumbsup:
Works for me, regardless of cost.


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## NickB (Sep 24, 2013)

I use a 14k BTU through wall unit in my 15' x 30' garage. I ran it for a couple months before insulating and it had no problems with taking it down 20 degrees in probably 20-30 minutes. With insulated walls and ceiling and an insulated 14' overhead door, I can run it at 64' when it's 85'+ outside and it still cycles on the t-stat (IOW, it would take it even cooler if I told it to).


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## tvman44 (Dec 8, 2011)

My shop is 20' x 20' with a lot of windows, walls and ceiling are insulated and I have a 18,000btu window unit. Does a fair job. :thumbsup:


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## NickB (Sep 24, 2013)

MT Stringer said:


> I have a11K BTU split system AC in my garage. We insulated the outside wall when the siding was replaced. 11 inches of blown insulation in the ceiling (R38). Energy efficient garage door (single car garage).
> 
> 94 outside, 74 inside. :thumbsup:
> Works for me, regardless of cost.


I've used both the portable and mini split systems and the splits are infinitely better units. 3 major reasons come to mind:

1) Footprint - the wall units take up very little space on the wall, no space on the floor and can be placed high enough for good cooling efficiency. A portable will need floor space + clearance around it.

2) Condensate - With a portable unit, you'll either buck up for a self evaporating model or have to deal with dumping, draining or pumping condensate. Mini splits usually are installed with a condensate hose coming through the wall with the refrigerant lines. 

3) Installation - A mini split requires a hole about 2-3" punched through for the condensate lines & drain tube. A portable needs 1 or 2 holes at 5". Since you're working in brick, that could be a big pain...

That said, if you're looking for the cheapest, temporary solution, the portables do work. I'd recommend at least shopping for a 2 hose system so that you're not venting you're cooled air outside. In your situation, I'd probably recommend the mini split over a through wall system.


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## MT Stringer (Jul 21, 2009)

I forgot to mention I used the mini split so the HOA wouldn't complain about a AC unit sticking through the wall. The condenser unit sits behind our privacy fence.


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## 44260 (Aug 29, 2013)

tBaker, I don't know what you go though up there as far as storms and power outages. I live an North of Baton Rouge and get power outages from some hurricanes that come through, have not had any direct hits yet but Katrina came awful close. But anyway I do have windows in my shop with 2 cheap 5,000 BTU window units from Walmart. My shop is not insulated, just cinder block walls and concrete floor but the ceiling is insulated. my shop is about 20x32 and it keeps the temperature down but still to hot to work in the day time. I go out early morning around 1 or 2am and work for 5 or 6 hours before the heat comes in. 

The point I wanted to make about the 2 window units is that if I have a storm and power goes out I can move the 2 window units to my house and easily run them off of my generator. I know its probably more of an expense then what you were planning on, but it maybe worth while to install 2 windows for A/C and move them to the house if need be

Something to think about


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## phoenixbound (Nov 24, 2014)

Do not use a portable AC! I had one and returned it. The problem is that all of the conditioned air is exhausted to the outside, which creates negative air pressure, which in turn, forces warm air to infiltrate the conditioned space. A window unit doesn't exhaust the conditioned air. It either recirculates it all, or there may be an option to bring in fresh air, but in either case, unlike a portable, it doesn't create negative pressure in the room.

I have a small window unit mounted through the wall of my 2 car garage. It keeps my shop comfortable on 100 degree days.


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## yank (Nov 15, 2006)

With a portable A/c unit, you need two ducts for outside inlet air and exhust to the outside for the condenser section. Done right, no air conditioned air should be leaving the room.


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## phoenixbound (Nov 24, 2014)

yank said:


> With a portable A/c unit, you need two ducts for outside inlet air and exhust to the outside for the condenser section. Done right, no air conditioned air should be leaving the room.



the LG units at Home Depot have ONE duct.


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## Leo G (Oct 16, 2006)

I put AC into my shop 2 years ago. Best thing ever. I come home smelling fresh and it's a pleasure to work in the shop now. I keep the thermostat at 73-75F depending on how hard the task at hand is.

My shop is a tough cool. A metal building with 24' ceilings, R13 insulation and a lot of solar gain. I put a 4 ton Rheem unit in the shop. During the hottest days it'll keep it at 75. That's if it's sunny. If it's cloudy and hot it'll keep it cooler. The solar gain from the roof is high. All radiant based. If I could get the roof insulated well the 4 ton could be replaced with a two ton.


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## hawkeye10 (Feb 18, 2015)

My garage shop is about your size and I have a window AC unit and a dehumidifer. I run them both 24 hours a day and have to empty the dehumidifer at least twice a day. I water the flowers with the water from the dehumidifer. With all the rain we have had this summer it's been really humid. I look at the money I spent on keeping the shop cool as just another tool. If I didn't have a table saw I couldn't do wood working and if I didn't have my shop cool I wouldn't go out there and work.

Don


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## difalkner (Nov 27, 2011)

About two years ago we had our two car garage insulated (two walls & ceiling) for $500. I planned to do it myself but just the materials were going to cost more than that and these guys were here and gone in 4 hours. I had already insulated the door with R11. It's a bit heavy but it doesn't get opened often.

I borrowed a 9,000 BTU portable AC unit to get a feel for how that might work. It didn't. I know it's a bit small but it was inadequate and there was the issue with condensate drain and opening a window to port the exhaust hose.

So, we had a 12,000 BTU, 22 SEER Gree mini-split installed - $2,500. This thing is awesome! It uses less current than my wife's hair dryer, is ultra quiet (not that it matters in my shop), and it does the job. It's been on 24/7 since October 2013 and our electricity bill hasn't increased. We do level payments and our bill was $155 before we installed it and it's still $155.

The garage/shop is on the west wall and has two windows. We put solar blocking film on the windows inside and 90% solar blocking screens on the outside across the entire west side of the house. Now that the shop is cooled/heated and the door into the house stays open most of the time I think that helps with the efficiency of the main unit so that probably contributes to the electric bill stability.

I keep the mini-split on 80 when I'm not in there and about 76-77 when I plan to work for a while. The big thing is the humidity stays where I need it for building acoustic guitars - somewhere in the mid 40's RH. In the winter I keep it on 64 but when I work out there for a while I bump it to about 67-68.

Here's the insulated door - 








Gree inside unit - 








Outside unit is so quite you have to walk up to it and see the fan running to know it working -


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## phoenixbound (Nov 24, 2014)

I insulated my garage door with 2" rigid foam panels (I don't want to replace the wood door because having a garage door opener is less of an obstruction than those darn rails on each side of a roll up door). the weight of the rigid foam is inconsequential and does the job. The biggest heat gain is from a section of the roof that isn't insulated. When I'm not making a lot of dust I can also leave the door to the house open to even out the temp a little--that's if my dog doesn't decide to keep walking into the shop which can be a hazard for both of us.  On the hottest days, the shop temp is around 77 if the AC was turned well prior to the hottest part of the day. My leather apron makes me quite warm so I'd prefer the shop to be colder , but for the less than $180 I spent on the AC, I can live with 77.


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## JMHubbs (Jun 1, 2015)

Tbaker1350,
Looks like most missed part of your question, dust from the shop getting into the unit and causing issues. I will address that. I would suggest you place additional filter material in front of the inlet of the evaporator coil (on window units this is where the filter is anyway). Saw dust, especially small particals of it, will plug up the factory filter on these pretty quick. Do you have dust collection? Does it work well? Needless to say, if you reduce airflow across evap coil, or condensor coil for that matter, you are lowering the efficiency of the unit. If airflow drops enough, the evap coil will freeze over. Neither if these are good. LOL I use the cheap rolls of blue filter media you can buy at big box stores, just cutting myself and holding it on cover with some self adhesive velcro strips. Does the job...


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## difalkner (Nov 27, 2011)

JMHubbs said:


> Tbaker1350,
> Looks like most missed part of your question, dust from the shop getting into the unit and causing issues.


Yep, I sure did. Look on the top of my unit and you'll see a blue filter. It catches a fair amount of dust before it hits the built in filters on the mini-split unit. I clean the internal filters about once a month but I don't typically have a lot of airborne dust. Plus, I built a shop air cleaner and it does a pretty good job to keep dust to a minimum.


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## IowaDave (May 21, 2015)

I have a simple, very small window shaker in my shop that keeps things cool enough to work out there even in the heat and humidity of the summer. (I am in eastern Iowa, so we see more humidity probably than extreme heat, relative to other areas of the country.)

My shop is 20' x 28', with 9' ceilings...but the key for me is that I have it very well insulated. No matter your cooling choice, I would really recommend making sure you have your shop well insulated.


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## Improv (Aug 13, 2008)

> If I could get the roof insulated well the 4 ton could be replaced with a two ton.


Spray foam insulation directly to the underside of a roof is called 'hot roof'. Not permitted on all structures, like our house we are building, but after I got the attic a sprayfoam vapor barrier (R-21) the walkout basement provides enough ac to keep the upstairs living area 10 to 15 deg cooler than outside.

Getting spray foam quote and keeping your 4-ton unit (it would save you money by not running for nearly as long to cool) would be two thing I recommend.

Regards,
Steve


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## difalkner (Nov 27, 2011)

Improv said:


> Getting spray foam quote and keeping your 4-ton unit (it would save you money by not running for nearly as long to cool) would be two thing I recommend.
> 
> Regards,
> Steve


If the unit is indeed too large for the allotted space it will, as Steve said, run less to keep the desired temperature. The downside is that it won't run long enough to dehumidify the space and that's the greater need for air conditioning is to remove humidity. 77 degrees in my shop at 45% RH is going to feel a lot cooler than 77 degrees in another shop at 65% humidity. 

This is especially important if you're building items that are more subject to wood movement. Build it in a 'wet' environment and take it inside a house with 'dry' environment and the piece will change dimensions more than you might think or for which you've allowed.


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## tbaker1350 (Jan 16, 2015)

*Thanks guys*

Thanks for all the feedback. I would like to go the fairly simple route and make a hole for a window unit, but I know the HOA would flip their lid over that. I was hoping against hope that someone had some success with a portable AC unit. As I suspected, that's not the case. I will most likely be going with the split unit, but that will have to wait until funding allows. Besides, I'm a new woodworker and not sure I want to make that much of an investment in my new found hobby. Worse case scenario, I'll just wait a few months till the weather cools off.


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## GuitarPhotographer (Jun 26, 2015)

My shop is in an old barn that can't be insulated easily, so I just work early in the morning when it's cool. When the shop temps reach the mid- to high 70s, I knock off and go in the insulated, air conditioned house.


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## Leo G (Oct 16, 2006)

92F outside today. Thank goodness I have the shop ACed. The non AC side was quite warm, not a pleasant thing to work in.


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## obfuscode (Feb 21, 2012)

You can go the portable A/C route but just make sure you get the 2 hose system - that takes care of the negative pressure issue phoenixbound mentioned. I have a 1 hose issue in my bedrooom and he's right, not only does it create negative pressure, it pulls in air from the bottom of the unit (the coldest) and uses that to cool the condenser then blows it out the window.

What's the ground around your shop like? I live on ledge rock but someday I plan to cool my shop using the method described on this page (the guy likes to write a book about every subject, you've been warned): http://mb-soft.com/solar/saving.html

TLR He buries 4" septic pipe a few feet deep into the ground in U shaped alleys at varying distances from his house, the air is pumped through them and uses ground contact to both cool and dehumidify the air.

Here's a diagram:


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## Toolman50 (Mar 22, 2015)

NickDIY said:


> I've used both the portable and mini split systems and the splits are infinitely better units. 3 major reasons come to mind:
> 
> 1) Footprint - the wall units take up very little space on the wall, no space on the floor and can be placed high enough for good cooling efficiency. A portable will need floor space + clearance around it.
> 
> ...


Nick,
I was very glad to see you like the split system. I'm planning to add A/C to my little shop. Do you have a brand you recommend? 
Thanks 
Jim.


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## NickB (Sep 24, 2013)

Toolman50 said:


> Nick,
> I was very glad to see you like the split system. I'm planning to add A/C to my little shop. Do you have a brand you recommend?
> Thanks
> Jim.


Jim,
The only brand I have personal experience with is Sanyo, whom appears to be out of the mini split business. My research came down to Mitsubishi, Fujitsu and Sanyo. The Sanyo won only because it was on sale at the time and was a great deal. I did the install myself and had an HVAC buddy purge the lines. The main unit came pre-loaded with refrigerant.
I've checked out a Mitsubishi setup at a friends house and it was a nice setup also and I wouldn't hesitate to recommend it. It doesn't seem like there's really much difference between he main brands. 

Depending on the construction and the siding on the shop, the through-wall is much cheaper ($600 vs $1200), way easier to install and works very well. If it's simple wood construction and vinyl siding, it's worth consideration.


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## cib (Sep 16, 2011)

tbaker1350 said:


> Hello all,
> 
> I live in north MS and the heat in my shop is getting pretty severe. My "shop" is my 2 car garage, roughly 20'x20' with no windows. The exterior walls are brick and I'm sure the walls aren't insulated. Above the garage is a bonus room which may or may not be insulated between the garage ceiling and floor space. I have tried using multiple fans and even making one of the homemade AC units seen on youtube with no relief.
> 
> ...


I'd recommend 1 of 2 directions. 1. get a window unit for the garage anywhere in the range of 7-12k BTU. 2. get a mini split system and install it and use it just like a standard A/C system, it would require some insulation but you could use it to heat and cool the shop as well.


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## tbaker1350 (Jan 16, 2015)

*Against all the good advice....*

So against all the excellent advice and suggestions you guys provided, I went with a portable AC unit. I know....why ask the question if you're not going to take our advice. Several reasons:


1 - Costs. First and foremost, overall price. As much as I would love to (and may eventually) put in a split unit, it just cost too much for me right now. This is a 12k BTU unit I found on Craigslist for $250. It was only a month old, used for two weeks, and original price was $400. 


2 - Simplicity - this was a quick and easy work around. I replaced a window in my garage door with a plexi-glass panel that I cut a hole in for a standard clothes dryer vent, bought a reducer to take the 5" exhaust vent down to the 4" exhaust tubing and that was pretty much it. It works, it connects and disconnects easily, and that's that.


Now, does it really work? Not as well as I was hoping, but it does help. My next step is to tint the windows of the garage door and place some insulating panels on the door. The late afternoon West sun beaming right onto that garage door is just overpowering what the AC unit can do. Again, another work around, but it's just going to have to do for now.


Overall, I think I made an OK choice. I am a new, hobbyist wood worker. At best, I get 1 to 2 days a week in my shop to work on projects. I have many more tools to buy (dust collection, band saw, planer, joiner, etc...) so I don't want to spend my money on an AC unit. The miserable heat will eventually go away, my need (desire) for other tools will not lol. 


So thanks to everyone for the feedback, it did not go unnoticed. If I continue down this fun path of woodworking, I will most likely put in the split unit. But for now I'll opt for slightly cooler but still warm.


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## difalkner (Nov 27, 2011)

Toolman50 said:


> Nick,
> I was very glad to see you like the split system. I'm planning to add A/C to my little shop. Do you have a brand you recommend?
> Thanks
> Jim.


We installed a Gree. Seems as though Gree makes mini-splits for other companies but also markets their own models. No complaints at all and less expensive than the big name brands.


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## woodnthings (Jan 24, 2009)

*get a silver tarp*

Get a sliver tarp that's a little bit wider than your garage door. Roll it up in a longer stick and hang it from two large hooks above the door. When you want to shade the garage just unroll it to the ground and it will reflect all the sun back into outer space. A second stick on the bottom that's screwed into the grommets will make rolling it back up easier.


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