# Portable AC for Garage Workspace



## Chas7715 (Dec 22, 2015)

Hi All,

My workspace (I can't really call it a shop) is one side of a three car garage. Here in OK we are sweltering with 95+ degree temps with over 85% humidity. Even in the mornings the garage is hot so doing any work out there is almost impossible. I tried it and I just sweated all over my tools. By the way, sweat is terrible for cast iron.

I have been contemplating buying a 10,000 BTU portable AC unit for this space. Has anyone used a portable unit? If you have, any feedback? Is this just a stupid idea? Please don't suggest a mini-split. No going to happen right now.

Help me out folks.

Chuck


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## clin (Sep 3, 2015)

I have not used one of those, and do like my mini-split (just had to say it). Those portable AC units still need to be vented to the outside. They draw in outside air to move across the condenser and then back outside again. A window is typically used. If you had a window, a more typical window AC unit may be less expensive.

As for the size, who knows?

It sounds like you would actually be cooling the whole 3-car garage (1000 sq ft or so). That's quite a bit for a sub 1-Ton AC unit in a probably not well sealed space.

More importantly, is the garage insulated? If not, I don't think it would do the job. First and foremost, insulate and seal.

If your garage doors are not insulated, insulate them. You can glue on foam board. Just don't over do it and add too much weight to the door.

Does the garage have a ceiling, or is it exposed rafters and you can see the roof sheathing?

If no ceiling, add one and insulate it. Or at least staple some of that silver sided bubble wrap type radiate barrier to the rafters. Silver side towards the roof. That would at least be a radiate barrier, minimal insulation, and a significant airflow seal.

And, perhaps you can add some plastic sheeting or other to divide the shop space from the rest of the garage. Just cool that side. It won't be as good as a full blown wall divider, but anything that keeps the cool air from easily flowing around the whole garage would help.


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## RichardHillius (Oct 19, 2013)

I have a portable AC unit that I use in the garage and I am not that happy with it. It just doesn't put out the volume of air needed to keep the room cool and more importantly the humidity down for my 20X20 garage space. My garage is not horribly hot as it has a insulated garage door and brick siding with trees around it but even than the unit I have I wouldn't recommend for that space. A window unit would probably work a lot better especially if you can do 220Volts.

The one I have is a 14,000 BTU LG unit I bought at Home Depot a few years ago for a rental house we lived in without AC that I repurposed when we moved.


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## joey502 (Mar 30, 2014)

I use a window unit and dehumidifier in my 24×24 garage. My walls, ceiling and foor are all insulated. The unit is a Frigidaire 12,000 btu unit from lowes. My set up will keep the shop at 70 when the temp outside is in the mid 90's and humity is 70%.

10,000 btu is not enough for that size space even if the garage is insulated. I think you will be very disappointed with it's performance.

The window unit would be better, the dust on the floor level is worse than that floating at window height. Buy a couplr if the cut to fit filters to help keep your unit clean and operating efficiently.


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## Chas7715 (Dec 22, 2015)

Thanks for the replies!

Situation:
No windows. Brick veneer, 2 exterior walls, insulated garage doors, back wall shared with insulated living space, rocked ceiling with no insulation in attic space. And no insulation in the two exterior walls (rocked as well).

So no window AC, which would have been done by now if I had a window.

Opinions seems to lead me to believe I should save my money and not buy a portable unit. And maybe insulate the garage space better in the interim.


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## dbhost (Jul 20, 2009)

I have had a portable unit for about 6 years now, ducted using 5" dryer vents through the wall segment between the garage doors. It is already failing, and dual hose units are hard to come by these days.

I am assuming you are in a windowless garage as I am. IF I were to do it over again, I would… And I am ALSO assuming that you can divide off your workspace from the rest of the garage. Get creative, lots of us do!

#1. Start with at LEAST 12K BTU. My Garage / Workshop is 18×20 which is really more like a 1.5 car, or 2 1980s Toyota Corolla garage size, with 8' 6" ceiling height, 
#2. Use a Window unit instead of a portable unit. The portables are extremely trouble prone.
#3. Build a manifold box, with a small squirrel cage blower to move air across the coils and in / out of the box.
#4. Mount the box / AC high up. Hot air rises, cold air sinks, cook the upper air first and it cascades down.
#5. Make sure you have a means to get the condensate (water that comes OFF of the air conditioner) out of the box without it touching the wood.

According to typical sizing charts, and let's assume you are in a space about like mine, and don't have the benefit of insulation like I went through the trouble and expense of installing, you will want a 12K BTU + 50% for efficiency loss due to no insulation, or 18K BTU portable unit. I know of none on the consumer market. That would mean your next option in portables would be 2 10K units that would suck up TONS of energy and be horrifyingly expensive to buy, maintain, and operate.

Window units have a higher operational efficiency and as such tend to need a lower rated unit for the same space, 10K BTU for each 20×20 space insulated, + 50% for non insulated, so 15K BTU.

At that point, you are looking at a 220v power requirement to operate.

If you haven't figured it out yet, I am trying to lead you toward the idea, insulation / radiant barrier is your friend in a hot climate. IF you can pony up the bucks to do a proper insulation job, do it! And then go through the steps above, separate your workspace insulated and dust separated as much as you can, and then go with a 10K BTU window unit in a box…

IF you have an actual window you can use, all the better!

Joey 502 is right, and I should mention, a LOT of it depends on actual dimensions. My shop space is 360sq ft with an 8.5 ft ceiling height giving me 3060 cubic feet to keep cool. His shop being 24×24 and I have to assume a 9ft ceiling as that is the standard, mine is short, is 576 sq ft, or 5184 cubic feet.

For what it's worth. My portable unit that is sick (Bad bearing I think) is a 12.5K BTU unit it struggles, a LOT to get the shop, insulated and sealed as it is, to 74 degrees when it is in the upper 90s / 90% humidity.

If I can't fix this unit, I WILL be doing what I said above, and build the cooling box for a window unit as my garage has no windows, and even if, the HOA would have a screaming conniption fit if I hung a Window unit out where it could be seen!


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## clin (Sep 3, 2015)

Insulate first. Keep in mind that with good insulation, even if you don't add AC, the space won't get as hot. Insulation evens out the temperature swings in a space. Of course, insulation isn't going to make it comfortable to work, just less miserable. But it will obviously give any added AC a fighting chance.

Also, when it comes to AC and humidity, bigger is NOT better. The longer the AC unit runs, the more humidity it will remove from the air. This is a common mistake when sizing AC for homes. Contractors tend to error on the high side (like 2 to 3X high). So you get a space that chills fast, but never dries out.

For a reference, I have converted a 3rd garage bay (12'x24') for my shop. I walled it off form the rest of the garage with a fully insulated 6" (R19) wall. Ceiling already had R30. Two other walls common to interior and converted the garage door to a double door with R13 insulation.

Low humidity where I live, but 105 F yesterday, and my 7,000 BTU/Hr mini-split just cruises.

Also, when looking at AC ratings, the BTU rating will be at one specific condition of outside temperature, set temperature, and humidity. So if possible get data on whatever you use and check what its performance is at your expected conditions.


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## ThistleDown (Jun 8, 2016)

I had one of those units in my switch room when I had my telephone business. It ran ALL the time and had to be vented outside, had to have condensation removed and was noisy as h-double-hockey sticks. Now you may think the noise is no issue in the shop but, we do not saw, drill, route, plane… the Whole time like this thing ran.

When I built my shop 2 years ago I got this, both heat and cool, and you can't beat the price. Could not be happier.
https://www.amazon.com/Koldfront-Heat-Cool-Window-Conditioner/dp/B00QXSC3V2/ref=cm_cr_othr_d_product_top?ie=UTF8

You can punch a hole in the wall like I did, otherwise this will go in a window. They also have smaller units, this one does fine in my 616sqf shop.


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## JeffP (Aug 4, 2014)

Maybe try to come up with a way to move well-filtered air between the main house and the garage?

Obviously there is a dust problem that has to be solved, but as far as base cost and cost of "installing it", seems like this will likely be the cheapest way to get the garage cooled down some.

Kind of depends on how much spare capacity the house system has too. Also maybe your house would rise in temp some, if it can't keep up.

Just a wild-assed idea to consider.


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## wapakfred (Jul 29, 2011)

I had just given my portable unit to the Habitat restore. I had windows in my shop, but they were very small and the largest window AC I could fit in there was 8K BTU. Add to that the fact both windows were exposed to direct sunlight most of the day. I thought the portable unit was just the ticket. I could get a larger one (12K BTU), it would work with the smaller window opening, and not be in the sun. Boy, was that a mistake. The 12K portable didn't cool as well as the 8K window unit it replaced. I'm only guessing, but the portable unit discharged a huge amount of air out the window, and the makeup air leaking in was the hot outdoor stuff. So it not only didn't cool, but it also didn't dehumidify. I used it most of last summer, and this spring gave it away. Tjis wasn't a cheap unit either. A Honeywell, and cost about twice what the window unit cost. Even so, if that's all you can use the decision is made. Just be sure to upsize it a good deal from what you think a window unit might be.


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## onoitsmatt (Mar 7, 2015)

I've been pondering the same issue for a couple of summers now here in Arizona. Same situation, no windows, brick construction. My latest wild idea is to fully enclose the third garage bay (mine has a wall partially separating it from the 2-garage bay). But where the overhead door is, build a wall a foot or so inside and mount a window unit in that wall. When in use, open the overhead door to let the hot air and condensate out. The issue is how to build a wall there that allows the overhead door to open.

Ducting inside a/c in garage is a code violation. You can't have car exhaust etc freely going in your house. Plus firewall is required between garage and living area.


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## Rentvent (Jan 28, 2016)

> Thanks for the replies!
> 
> Situation:
> No windows. Brick veneer, 2 exterior walls, insulated garage doors, back wall shared with insulated living space, rocked ceiling with no insulation in attic space. And no insulation in the two exterior walls (rocked as well).
> ...


Unless you can get the laws of thermodynamics changed, any type of active cooling will require penetrating a wall or ceiling to vent the heat. The advantage of the split or ductless system is that the penetration is only one or two 1" holes.


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## Chas7715 (Dec 22, 2015)

Thanks for all the replies/suggestions/general help!!!!
This is why this forum is the best!!

I have an A/C company coming on Friday for a quote on a mini split. We'll see if I survive the shock! And I think I jinxed myself with all this talk about A/C as I had to layout $400 last night because my house A/C crapped out.

As for insulating, all of the garage walls and ceiling are sheet rocked. I can blow in some insulation in the ceiling. Should I tear off the sheet rock on the walls to insulate with blankets or attempt to blow in insulation in the studs cavities? If so, is that a DIY job?

DBhost: can you provide more details concerning a manifold box and a window unit??

Thanks all,

Chuck


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## clin (Sep 3, 2015)

> Thanks for all the replies/suggestions/general help!!!!
> This is why this forum is the best!!
> 
> I have an A/C company coming on Friday for a quote on a mini split. We ll see if I survive the shock! And I think I jinxed myself with all this talk about A/C as I had to layout $400 last night because my house A/C crapped out.
> ...


Mini-split is going to be some thousands of $$$, but you'll know soon enough. I'd get more than one quote. I had a system put in last August (one outdoor unit feeding three indoor units, one in my converted garage shop space). It was a bit over $7k. That's of course more than you would be doing. But I had quotes of $20 K.

Also, even the guys I went with initially quoted my much larger units than I needed. That's why I did my own Manual J calculation. In the end, had them put in three of the smallest Fujitsu units possible (7,000 BTU/hr). We've recently had as hot a weather as we get, and as expected, they have handled it just fine.

If you don't run a Manual J calculation, sizing the system is just guessing, no matter what they say. There are too many variables. Doesn't matter what your neighbors house needed. Unless the situation is identical, what works for one won't necessarily work for the other.

If you don't run a Manual J calculation, you will almost certainly oversize it.

You don't want to over size any AC system, but you really don't want to do it with mini-splits. Sized properly, they can be very efficient. Oversized, and they aren't going to be much better than a common full on/full off AC unit.

Plus, if oversized, they won't dehumidify well.

Keep in mind mini-splits are really meant for continually cooling a space. If what you have in mind is just cooling things down for a Saturday afternoon and leaving it hot the rest of the week, I'd cut a hole in the wall and just stick in a powerful window unit. Do it right so you can convert the hole to a Window so the house won't look weird when you go to sell it.

As for insulating. If the wall cavity is a full 2×4 sized space, I'd consider blowing in insulation. But make sure it is appropriate for your area. You can create moisture issues without a vapor barrier.

But it's not the worst idea to pull off the sheet rock, insulate with batts, then replace the wall board with plywood. Not of course the wall common to the inside of the house, that needs to remain a fire wall with appropriately thick sheet rock.

Are you think of cooling the whole garage? Or are you going to partition it somehow. That will make a huge difference on what size AC system you need.


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## KelleyCrafts (May 17, 2016)

> I ve been pondering the same issue for a couple of summers now here in Arizona. Same situation, no windows, brick construction. My latest wild idea is to fully enclose the third garage bay (mine has a wall partially separating it from the 2-garage bay). But where the overhead door is, build a wall a foot or so inside and mount a window unit in that wall. When in use, open the overhead door to let the hot air and condensate out. The issue is how to build a wall there that allows the overhead door to open.
> 
> Ducting inside a/c in garage is a code violation. You can t have car exhaust etc freely going in your house. Plus firewall is required between garage and living area.
> 
> - onoitsmatt


Matt, I don't recommend going through the cost or trouble in AZ. I have put a ton of research into this and in our climate (low humidity) it's really not worth the expense of the full on AC unit and all of the work. Your situation might be similar but I have a side door on my garage I crack open about 10" and I have a portable swamp cooler I use in front of that door. I crack the garage door about 3 inches to let the air move through.

I'm not saying it was like sitting in my living room this last weekend but it was extremely tolerable. Especially with temps hitting 120 degrees on Saturday. With low humidity an evap cooler is perfectly fine and a lot less hassle overall. I picked a Honeywell up at Lowes for about $400 and the wife found a coupon for 10% off total purchase.

The original poster has the real issue. Heat sucks but humidity + heat really sucks.


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## onoitsmatt (Mar 7, 2015)

Thanks for the input Ki7hy. I've got a big portable mastercool that i bought last year. I haven't used it in the shop yet. I'm primarily a hand tool shop and am concerned about the rust. Also added humidity to the shop and its affect on dry wood. Have you had any trouble with either of these with your evap?


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## Chas7715 (Dec 22, 2015)

Clin,

Excellent input! I thank you!

I cannot punch a hole in the wall of the garage for an AC unit. The HOA would run me out of the neighborhood. That is why I was exploring a mini split. I will be getting more than one quote. that's an absolute!

I'll post back after I get my quotes. Thanks all!


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## dbhost (Jul 20, 2009)

The manifold box is, for all intents and purposes simply a box that mimics passing through a window, and then in turn separated into 2 segments, so the unit is sealed fully around in 2 places, one where it passes through, and the second between the intake and exhaust sides of the coils. Fittings for hoses to intake and exhaust air would be installed, and then routed. I would use 5" HVAC duct fittings so you can use 5" insulated ducting. Use a blower on the exhaust side to keep air exchanging over the coils.

I wish I could find the post, I saw it on Sawmillcreek maybe 5 years ago… Looked like a good idea but I already had a portable unit.

Some guys run a box up to vent into the attic and in / out the soffits.


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## bobasaurus (Sep 6, 2009)

After insulating my one car garage, it's been about 70-75 degrees in there even when it's 90+ out. Made an attic space after drywalling the ceiling, then blew in cellulose. Also upgraded all doors and windows to the best insulating ones I could find.

It gets hotter as I work in there and my high power fluorescent bulbs put out heat, so sometimes I open the door to the main house and the garage window then let my evaporative cooler blow air through.


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## KelleyCrafts (May 17, 2016)

> Thanks for the input Ki7hy. I ve got a big portable mastercool that i bought last year. I haven t used it in the shop yet. I m primarily a hand tool shop and am concerned about the rust. Also added humidity to the shop and its affect on dry wood. Have you had any trouble with either of these with your evap?
> 
> - onoitsmatt


I use a lot of hand tools, I keep them well waxed though. I have about 12 hand planes in the wall cabinet and they are fine. During monsoon season coming up is when the cooler won't work and that's where an AC would be good but honestly, pricing an AC in the garage and insulating, etc. I could be buying good hardwood for that money! So a swamp cooler is what I have and I'm as pleased with it as I could be. Wish it were better but very tolerable. Like I said, I spent the whole weekend last weekend in the garage. I did break a sweat here and there planing but I do that in the winter in the garage.

Oh, and I don't run the evap cooler 24/7 so it's dry again out there in no time flat. I'm a weekend and sometimes evening worker so it's off more than it's on.


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## bigJohninvegas (May 25, 2014)

I was quoted $2500 last year for a mini split for my 3 car size shop. That's a small 3 car at 22X30'.
Was more than I could do at the time so no a/c for me yet. I do have a fully insulated shop, and it really helps.
Today it is 110° and about 10% humidity here in Las Vegas. Yes, a dry heat. My shop, with 2 fans running is about 90 at 5pm. Friends with now insulation here seem to have temps 15 to 20 above outdoor temp.

Insulation is everything. With the sheet rock in place you can use a couple different insulation products.
I have seen both the blown and a spray foam type. A friend had a finished garage with no insulation. They came in and drilled holes in the sheet rock a used some sort of spray foam insulation, then patched the holes. Made a huge difference. If you have attic access you can use anything you want. 
Please let us know what your quote works out to be for a mini split, and good luck.
Final thought, a/c quotes a cheaper here at winter time. With luck this will be my last hot summer in The shop.


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## TheFridge (May 1, 2014)

I have a small portable LG vented outside. It's ok when it's pointed directly at me but that's about it. Better than nothing when it's 100 degrees outside plus humidity.


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## moke (Oct 19, 2010)

I have had a similar situation to the others that have used the portable air conditioners. I however, was a little dumber than they were, I actually bought a second portable air unit thinking it would help….now I own $700 worth of useless junk….I do have two small windows and I found a 10k unit that I put in one of the windows at Sams of all places. It works great…I think it is a little undersized for my 900 sq foot shop so I am using one of the portable units and now life is good. Well, except for the colossal waste of money that I could have bought tools with!!!
Mike


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## Finn (May 26, 2010)

I had a similar set up. I put up an insulated wall to separate the garage from my workshop. I blew in insulation into the wall and ceiling, insulated the roll up door and installed a portable unit. It did not to the job for long. Plugged up with saw dust! I then installed a window unit in my new wall that put the hot air into the garage part. That worked very well. I recommend that. I am in a low humidity area (west Texas) but in a higher humidity area like Oklahoma you need to leave the Air conditioner on all the time to keep the humidity down. By all the time, I mean 24/7 all summer long.


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## rwe2156 (May 7, 2014)

I'm in the same boat as you except its not a garage, its a 1200SF shop in a converted horse barn with metal roof.
I have plenty of fans and an 8' sliding door, but when its 97, you're just blowing hot air around.

What I did is build a 1416 room in one corner insulated walls and ceiling and with a 8000 BTU window AC it is an absolute lifesaver. I keep all my hand tools and a workbench in there.

Could put up a couple prefabbed walls in a corner of your garage, even 10X10 would be something?


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## joey502 (Mar 30, 2014)

> I had a similar set up. I put up an insulated wall to separate the garage from my workshop. I blew in insulation into the wall and ceiling, insulated the roll up door and installed a portable unit. It did not to the job for long. Plugged up with saw dust! I then installed a window unit in my new wall that put the hot air into the garage part. That worked very well. I recommend that. I am in a low humidity area (west Texas) but in a higher humidity area like Oklahoma you need to leave the Air conditioner on all the time to keep the humidity down. By all the time, I mean 24/7 all summer long.
> 
> - Jim Finn


I have a humidity problem here in Ky. I use a small dehumidifier when the a/c is running. The a/c seems to run much less with the humidty down to 50%. I also have 2 - 16" oscillating wall mount fans the help circulate the air. It may seem like a lot going on but it works beautifully.


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## OSU55 (Dec 14, 2012)

Does the HOA contract specifically prohibit window air conditioners?


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## Rayne (Mar 9, 2014)

Following as I have the same issue. I'd like to see what the final quote is for a full split mini install. Not to take over this thread, but anyone know how much it is to insulate a garage and attic? And what kind of garage door insulation are you guys talking about? I have the foil on the door which does help, but not in this weather and humidity in FL right now.


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## clin (Sep 3, 2015)

> Following as I have the same issue. I d like to see what the final quote is for a full split mini install. Not to take over this thread, but anyone know how much it is to insulate a garage and attic? And what kind of garage door insulation are you guys talking about? I have the foil on the door which does help, but not in this weather and humidity in FL right now.
> 
> - Rayne


For insulation cost you just have to price out the cost of material for your size garage. Assuming you're going to DIY. But you should be looking at hundreds, not thousands.

When I insulated a garage door years ago, I just glued on Styrofoam to the garage door panels. Made a huge difference. But that door was a simple sheet steel door. So anything was going to improve it.

Something with a foil (foil facing out, not against the door), would be a bit better still. But watch the weight. Garage doors use springs sized to the weight of the door. If you add too much weight, you need to increase the spring size.

But generally, light weight foam shouldn't be an issue.


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## Finn (May 26, 2010)

I also used Styrofoam on the roll up door. IN my case I did not even have to glue it in place. I slipped in two layers of 3/4" Styrofoam. I rented an insulation blower from Home Depot and insulate the attic and the one outside wall, with blown in insulation.


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## Rayne (Mar 9, 2014)

> Following as I have the same issue. I d like to see what the final quote is for a full split mini install. Not to take over this thread, but anyone know how much it is to insulate a garage and attic? And what kind of garage door insulation are you guys talking about? I have the foil on the door which does help, but not in this weather and humidity in FL right now.
> 
> - Rayne
> 
> ...


Cool, I can deal with hundreds to insulate the attic and from what Jim said about renting an insulation blower, this might be doable. I have a garage door insulation kit with the padded foil. I should have detailed that out further before. I was curious about the deal with the surrounding outline of the door itself minus the bottom which has a rubber seal. I guess it won't make that big of a difference if everything else was insulated? most of 3 sides of my walls are concrete and not sheetrocked. I read somewhere that you can insulate concrete itself, but it's porous by nature, so not sure how effective that would be. Thanks for the info. It gives me somewhere to start.


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## bigJohninvegas (May 25, 2014)

I paid for garage insulation when my house was being built. The doors are the type with four metal panels, and are insulated with what feels like a styro foam covered in a prtective plastic layer. I have helped both my dad and another friend use 1 inch thick styrofoam panels. We just used liquid nail to glue them to the metal door. The springs had to be adjusted on the one car door and upgraded to a larger spring on the two car door. Light weight styro made a big difference in the balance of the door.


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## Chas7715 (Dec 22, 2015)

Following up here: The quote I received for a 2 ton mini split was close to 5K. Now looking for more bids! 
I might wait until winter when their prices drop significantly. It'll also be a lot more comfortable when I blow in the insulation!!

To OSU55: Any modification to the original structure as built requires approval of the HOA Board of Governors. Trust me…that ain't gonna happen. Also, I'm not too keen on punching a big hole in the wall anyway which is why I'm on the hunt for an affordable mini split install.


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## Lazyman (Aug 8, 2014)

I'm late to this thread but I thought I would just chime in with my experience. A friend "permanently loaned" me a Soleus Air 14000 BTU portable A/C with heat that runs on 115v standard plug. He bought it off of Craigs list for a little over $200 about 4 or 5 years ago and this is my 3rd summer with it. I live in DFW area and we have frequent 100 degree days during the summer. My 20×20 garage is similar to yours, no insulation on exterior walls or ceiling with 2 common walls with house. I have 2" of Styrofoam insulation on the metal garage door. My ceiling temperature during the late afternoon as measured with my infrared thermometer was 110. Note that the roof pitch and garage door faces west with no shade in the afternoon. I cut a hole in my ceiling and added 4" of rolled insulation and the ceiling temperature dropped to mid 90's at worst. I simply vent the A/C exhaust under the garage door using a 2×4 to seal most of the gap and put a pool noodle to cover the gap left at the top to keep hot air from rising up the metal door into the garage. I am thinking about buying a couple of garage door exhaust ports to vent the air through the door so that I can put the door all the way down to get less leakage.

Over the last week or 2 we have been seeing 100+ temperatures and this A/C is able to keep the garage from getting above the mid-80's as long as I turn it on first thing in the morning. While by mid afternoon I still sweat some, I find that running an extra fan helps quite a bit and I never sweat so much that it drips off of me. I usually knock off around 4 pm on 100+ days but if the temps stays below 100, I can stand it well past 5:00 even with the heat beating down on my western exposure.

My recommendation is to look for someone selling one of these portable units on Craigs list. You will frequently find someone who bought one because their home A/C went out and needed something temporarily. If you can find one that has the heat option, I also recommend that. While I have a small space heater mounted over my workbench, it really only creates a small warm zone. The Soleus Air's Heater function does a pretty good job of making the entire garage tolerable on all but the coldest winter days too. I would spend a little extra for that feature.


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## OSU55 (Dec 14, 2012)

I didn't see what your sq footage is, but you might consider a regular split ac or heat pump. Goodman goes down to 18K I think, and they have a small one where the indoor blower unit can just be hung on a wall. A single supply duct should be ran across the room for distribution, but not absolutely necessary. I mention heat pump since you might as well plan on heating as well as AC. While it may be oversized for your application, I suspect one of these small split systems may come in around $3000-$3500 because there isn't much to the install.


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## clin (Sep 3, 2015)

> Following up here: The quote I received for a 2 ton mini split was close to 5K. Now looking for more bids!
> I might wait until winter when their prices drop significantly. It ll also be a lot more comfortable when I blow in the insulation!!
> 
> To OSU55: Any modification to the original structure as built requires approval of the HOA Board of Governors. Trust me…that ain t gonna happen. Also, I m not too keen on punching a big hole in the wall anyway which is why I m on the hunt for an affordable mini split install.
> ...


A 2-Ton system seems too large to me. As I'm sure I said earlier in this thread, without a Manual J (or similar) calculation, sizing is a guess. I'm assuming your 3-car garage is about 900 sq ft (not sure if you said that somewhere in this thread).

At 2 Tons and 900 sq ft, that's 450 sq ft/ton. Even the very conservative guesses are in the range of 500-600 sq ft/ton. And those are almost always much too conservative. But you have two exterior sides walls, and a garage door wall. So it might be okay, but even at that it seems too large.

The problem with over sizing is the unit costs more AND it will run less efficiently AND it won't dehumidify as well.

For grins, I'd be willing to take a crack at a Manual J calculation for you. It's not really that hard for a single space. I won't guarantee the calculations, but it would at least get you a realty check.

I would need to know what city you live in (for weather data) the construction of the garage (dimensions and length, height and construction of ALL the walls and ceiling and roof, windows, window type, size etc.). Also, if you have anything else in there like hot water heater.

Also, I would assume the concrete slab is not insulated since it is a garage. So unless you know otherwise, I would assume not.

Also, the direction of each wall. The assuming it is a rectangular space, just knowing that the garage door is on the south east tells me all I need to know.

Again, I'm no expert, but have done this for myself, and this has me curious what it would take for you.

There is a spread sheet for this that the ACCA has for this:

http://www.acca.org/communities/community-home/librarydocuments/viewdocument?DocumentKey=0bc73e80-6c3c-43cb-bdb2-43316a380fa4

This is what I would use. But you need the inch thick Manual J book to know what to put in the data fields. I'd certainly give you that spread sheet so you'd have it.

Let me know. You can PM me the info or put it up here. Either way works. If we do it in public, so to speak, it might be informative to other LJ members.


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## SignWave (Feb 2, 2010)

If you're handy, you can buy one of the mini-split systems online and install it yourself. Shop for yourself, but I just found a LG 22,000 BTU 20SEER ductless heat pump for under $2K. You may need a few accessories, and you'll need to run power to it. You will also need to pay a service call to an HVAC company to vacuum/purge the lines. Not for everyone, but I'm sure that many people on this site could manage it.


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## kelvancra (May 4, 2010)

Like Clin said, focus on insulation first. Our summer weather often runs over a hundred. I just have a window unit, until I get another hundred or so amps in the shop. Even without honest ceiling insulation and without rock on yet, I get up to a twenty-five degree difference in my thousand square foot shop. Once I get rock on the ceiling and the wall separating the play area from the two car stalls the efficiency of the window unit should be very impressive.

Today it was 105, but the shop maxed at 86.


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