garage air conditioning

[Crawdad]

First thing i would do is, if possible, insulate the attic. Make sure it is vented appropriately too. They make blankets for noninsulated garage doors. They are lightweight but look sorta tacky. I plan to glue styrofoam sheets to my garage door and go up one or two cranks on the doors spring to compensate the addl weight. Wont look pretty but some cheap paint may help.

I did the whole car radiator and lawn hose thing. It works very very well but its a hassle sometimes and you tend to over water the grass. Glad to have a well but can burn it up as well. Plus there is two hoses going in and out of the garage while it runs. It was a fun project but junked it after my brazing joints started to leak. This was way before i joined the AF, im a better welder now!

I am rebuilding my garage and have put 6" insulation in the walls and attic. It stays cool by itself till i open the garage door. Its about a 24x20 and i plan to go the portable unit direction. Yeah it wont get down to 68 degrees on a 100 degree day but if i can get it in the hi 70s ill be happy. Portacoolers are huge and they tend to promote rust parties on everything that has an exposed finish. They killed our machines and tools in the desert, a maintenance nightmare.

Good luck and would like to hear what you decided to go with. Im subscribed!

 

[distended]

Thanks to everyone for the input, defenatly be staying away from the portable ones and probably go with a window type unit.
My garage is only 500 sq. ft. and the side is mostly behind our block wall so I can install it there and not have to worry about the HOA, just not really to thrilled about cutting a hole in the side of the house.
I'm going to do a little more research on those mini splits as well as the attic vent fan thing. How can I figure out if my houses unit can handle the exra space beings required to cool? Will that reduce its efficiency in cooling the rest of the house? I really like this idea but don't want to spend this money doing the attic vent fan and running ducting to find out that the rest of the house takes longer to cool off and the a/c is running constantly and I still need anither unit for the garage anyway, you know?

 

[blubuckaroo]

Go big. A garage can't be insulated as well as a house. You have a metal door with only about 3" foam, rubber seals all around that can't be insulated. You're not leaving it on all the time so you want something that will do the job when you want to wrench. Pull in a hot car and you've just added to the load. And you're in Phoenix too. I wouldn't bother with anything less than a 2 ton (24000 BTU) unit.

 

[deltarat]

I have a 30x50 with 15' peak open trusses. I run 2-25k window units @$500 each. They take out the high humidity here and keep out the SKEETERS.

 

[AZ73]

Thanks to everyone for the input, defenatly be staying away from the portable ones and probably go with a window type unit.
My garage is only 500 sq. ft. and the side is mostly behind our block wall so I can install it there and not have to worry about the HOA, just not really to thrilled about cutting a hole in the side of the house.
I'm going to do a little more research on those mini splits as well as the attic vent fan thing. How can I figure out if my houses unit can handle the exra space beings required to cool? Will that reduce its efficiency in cooling the rest of the house? I really like this idea but don't want to spend this money doing the attic vent fan and running ducting to find out that the rest of the house takes longer to cool off and the a/c is running constantly and I still need anither unit for the garage anyway, you know?

1) If you don't want to cut a hole in the wall, go back and read my first post. I run it from under the garage door - in Scottsdale, same temp as Phoenix, and my make-shift system with my 12,000BTU unit does fine. Feel free to PM me and you can come over and see for yourself. It's going to be 105-107 over the next 3 days. That being said, it still gets down to the mid 70's at night so I'm not starting out with a garage that's 100 to begin with. If I'm working in the garage that day, I'll go out in the morning and turn it on. The garage stays cool all day. I'm assuming that if I turned it on from 100 to start, it might take 3 hours to cool down to 75 or 80, just like my house would. Doubling the BTUs would make it cool down in 1.5 hours instead.

2) my garage has the same insulation as my house EXCEPT for the attic. Garage doors with insulation are usually rated by their manufacturers at around R-16. Of course that's the INSULATED part. Taking into account the hinges and gaps the tested value is R-6-7. A low-E dual pane argon gas filled window has a R 2.7-3.6 value. Your insulated garage door has twice the insulated value of your windows. You, as I and others have noted, have to make sure you seal your gaps around the door. I use the standard vinyl overlap on the sides of most garages

3) You cannot run a duct to the garage from your house without putting a return vent back to the system unless you left the door between the house and the garage open.

4) VERY basic rule of thumb is 1 ton per 500 square feet. Most houses are slightly over that tonnage on their a/c, but not usually a whole ton as it makes them cycling too often which drives up the cost. There are web sites that can help you calculate the amount of BTUs you need for your specific situation. This is the one I used:

http://www.cooloff.org/sub_cool.html

5) a mini-split is an EXCELLENT choice, but will require dedicated wiring and breaker (they're usually 220), a cement pad, and a 3-4 inch hole in your wall. It's not just the unit, it's the installation. You might have to spend another $2-300 getting it wired to code.

6) More isn't necessarily better. We live in a dry climate so the A/C is more efficient here except during monsoons.

7) If you're going to be pulling in a hot car and expect an a/c to keep up with it, you're kidding yourself. A car that has been running puts out an enormous amount of BTUs for a long time. You would need a massive A/C to overcome it in 500 square feet. You'll be trying to cool a car that's 200+ degrees under the hood

 

[56f100bbw]

3 ton mini split

Added a 3 ton mini split to my shop last week all ready has a 3 ton central Rheem on a wi-fi hook up nice and cool now when it really hot this time of year

 

[Glass Pony]

Got this for my birthday last week from BJ's, 8000 btu for $189. It's struggling but it's keeping my 500 sq. ft. garage at 80 degrees with no humidity when outside it is 95 degrees and 75% humidity.
It's not cool enough for sleeping, but a lot better working in it.

 

[Broncobowsher]

This post has been brought back to life after sitting for 6 years.

I live in AZ, have a 660 ft 3-car garage full insulation package. 2½ ton split system, just like a regular house unit. It does OK. If I fire it up in the morning it will keep it all day. If I fire it up in the afternoon, I can do light work in the evening. There is a lot of thermal mass. concrete floor, tool boxes, engines, etc. Takes a lot to cool all that stuff but holding temp once there isn't too bad. Bring in a hot car, forget it. There is a lot of thermal energy in a couple tons of hot vehicle. I once did some math, figured a weekend day of playing in the garage with the A/C running 100% was about $10 a day. Probably a little more these days. Heat pump gets fired up a couple times in the winter, no supplemental heat, the resistor wires were removed.

I can get the garage colder than the house. Not quickly but eventually. Seen plenty of window A/C units installed in walls. Does a great job of make unbarable into just a warm garage. Have not run a mini-split. I worry more about airflow. I have 4 vents spread through the garage. In the winter I need a fan for vertical circulation or the temps stratify into layers.

My old house had a 3¼ ton package until on a slab next to the garage with holes in the wall. Vertical duct up and out at the top. It was just a 2-car garage. All the cooling was in one corner. High flow fan, not a gentle breeze off a mini or a couple vents off a window unit. It did not evenly distribute across the garage. I had to add a trunk line to the far corner to get some air over there. Better but still not great. That is why the new garage got 4 vents spread all over.

 

[Timmy390]

I know it's not in the OP's budget but is no one running a "Bard" unit on their shop? I'm looking at cooling my shop (1152sqf) and through my research a Bard unit seems to be the way to go. They come in AC only or a heat pump version. Price is the only thing holding me back.

I need to look at those ductless units....they seem to be gaining in popularity.

To the OP, if cost was a factor and it's always a factor, I would go with the biggest window unit I could get for the money I wanted to spend. I noticed my local Lowes had a unit that said it would cool 1200sqf for right at $600.

Tim

I ended up going with a BIG window unit from Lowes. It works much better than expected. Today high with heat index factored in is between 100 and 110 outside. My shop is set at 75 and per the thermometer it's there. 46% humidity in the shop.

I could keep it lower and have but the monthly bill is a factor. I don't run it at night.

Best $600 I've spent in a LONG time

Tim

 

[Pa PITT]

Wow I put a 40K UNIT IN a big room equal to a garage when I had a house in town .
It was a 220V Unit but guess what It cooled it down & cycled fast . If you get a extra good garage door you could even get open the door & share with the house. If the wide ain't home .

 

[Broncobowsher]

The garage A/C is plan C, that is after Plan B of sleeping in the other half of the house with a separate A/C fails. Since the first 2 A/C units are the same age you never know.
Plan E is sleeping in the car in the back yard with the A/C running, only likely if the power goes out. Oh, plan D, go to work and sleep in the corner of a conference room. You always need a backup plan if you loose A/C in the house.

 

[sprdv1]

Added a 3 ton mini split to my shop last week all ready has a 3 ton central Rheem on a wi-fi hook up nice and cool now when it really hot this time of year

AC is a Plus

 

[sprdv1]

The garage A/C is plan C, that is after Plan B of sleeping in the other half of the house with a separate A/C fails. Since the first 2 A/C units are the same age you never know.
Plan E is sleeping in the car in the back yard with the A/C running, only likely if the power goes out. Oh, plan D, go to work and sleep in the corner of a conference room. You always need a backup plan if you loose A/C in the house.

yes sir, especially in your neck of the woods...

 

[bigmuddy]

Keep in mind a good bit of you being comfortable is removing humidity.
If you go to large, (not I think this is a problem with a garage) You will cool down the area and be wet and clammy. If it will draw the humidity then you can usually keep the thermostat up and save a few bucks.
Frankly I have been considering the idea of a large window unit myself or a PTAC unit (similar to what they use in most Hotels) They work pretty decent but can be energy hogs and well they are not cheap either. Makes for a cleaner install than a window unit though.

 

[Timmy390]

Keep in mind a good bit of you being comfortable is removing humidity.
If you go to large, (not I think this is a problem with a garage) You will cool down the area and be wet and clammy. If it will draw the humidity then you can usually keep the thermostat up and save a few bucks.
Frankly I have been considering the idea of a large window unit myself or a PTAC unit (similar to what they use in most Hotels) They work pretty decent but can be energy hogs and well they are not cheap either. Makes for a cleaner install than a window unit though.

My window unit works REALLY well. I was shocked as to how much humidity it removes. I was just out in the shop. 75 degrees and 46% humidity. Outside temp is 90 degrees with a feels like 101. Feels so good in there......I just bumped it down to 72 and my SNL is here working on his Samurai and I'll be out there soon (or plan to be).

I looked at the PTAC unit (similar to what they use in most Hotels) but to be honest, the window unit is a really clean install nearly flush with the wall I stuck it in. I wanted a Bard unit but it was an install thing.......My window unit has heat......well It's not much heat at all but it helps. I really just use the fan to move air which made the small portable propane heater I use much more efficient.

Tim

 

[mustanggarage]

My window unit works REALLY well. I was shocked as to how much humidity it removes. I was just out in the shop. 75 degrees and 46% humidity. Outside temp is 90 degrees with a feels like 101. Feels so good in there......I just bumped it down to 72 and my SNL is here working on his Samurai and I'll be out there soon (or plan to be).

I looked at the PTAC unit (similar to what they use in most Hotels) but to be honest, the window unit is a really clean install nearly flush with the wall I stuck it in. I wanted a Bard unit but it was an install thing.......My window unit has heat......well It's not much heat at all but it helps. I really just use the fan to move air which made the small portable propane heater I use much more efficient.

Tim

This is just a testimonial of what can be done when you don’t have a choice. I have a 40 x 60 foot steel shop the walls and doors were insulated when it was built. My daughter wanted to have a birthday party out ther when she was about 12. Her birthday is in July. July in Iowa can be miserable 90-100 plus days with 90 plus humidity. It was miserable in the shop so since she asked me to have the party in the shop a few days before. I went and bought a 15000 BTU window air conditioner from sears. Stuck it in the winDOw and put my 36 inch fan on high and let it run. Kept all the doors shut and you would be amazed how comfortable it is out there. I have always planned to put in a real hvac system some day, But heck as long as I don’t open the big doors too often it keeps it comfortable all summer long. And I am fully aware that it is way toosmall to cool that big space. But it does