Posted on Aug 14 2013 by There are three air conditioning vents in this garage in Austin, Texas, and the ducts come from the from the main system in the house. Not only does this set-up violate the building code, but it can cause indoor air quality problems. Sometimes people do the craziest things. Take that photo at right, for example. That's a new home being built in Austin, Texas. The arrows point to three air conditioning ducts. Yes, they're air conditioning the garage. Mistake #1: Air conditioning the garage Now, the first mistake here was probably adding air conditioning to the garage in the first place. Most of the time, a garage is used simply as a garage. That is, the homeowners store cars, lawn mowers, high school yearbooks, a Smoking Donkey cigarette dispenser, a 'time capsule' in a shrimp factory box that you've had since your first job in high school, and that old Mr. Microphone. (Hey, Good Lookin', we'll be back to pick ya up later!) If it's just going to be used as a garage, there's no need to air condition it all.

It's a waste of energy that will provide the owners little if any benefit. If they've got some really valuable stuff that can't take the heat or humidity out there (like that Mr. Microphone), then bring it into the house. How to Heat a Garage Should I Insulate My Garage Door? Why is it a waste of energy? Because cars, lawn mowers, and junk don't need to be air conditioned. Also, standard roll-up garage doors aren't insulated or air-sealed, so you're paying to condition space that's constantly reheated by Mother Nature, especially if those doors get direct sun during the day. Are there good reasons to air condition a garage? If I'm a woodworker and don't care if my cars sleep in the driveway, I'd air condition my garage in Austin. Or if I want to turn it into a mancave, momcave, or teen hangout, it's definitely gonna chill. Or maybe you can't build a house in a certain price range or Austin neighborhood without air conditioning the garage and have any hope of selling it.

Mistake #2: Air conditioning the garage the wrong way OK, so let's say you've got a good reason to air condition the garage. That's fine, but you should absolutely never, ever do it the way they did here. Matt Risinger is an Austin home builder who owns Risinger Homes and does things the right way. The photo above is from a video he made to explain the problems with air conditioning a garage the way this builder did. The big potential problem here is bad indoor air quality. Let me show you why. An air conditioner is supposed to be balanced in its air flow. A 3 ton AC pulls 1200 cubic feet per minute (cfm) of air (nominal) from the conditioned spaceInsulated, air-sealed part of a building that is actively heated and/or cooled for occupant comfort. and then puts 1200 cfm of air back into the conditioned space. What Matt showed above is a system that puts maybe 400 cfm of air into the garage. It's still pulling 1200 cfm from the house (assuming a 3 ton system) but only has 800 cfm left to put into the house.

Hmmmm. 1200 out, 800 in. That’s like having a 400 cfm range hood running whenever the AC kicks on. 3 ton all in one ac unitThat's gonna depressurize the house.best central heating and cooling systems reviews One of the basic rules of air flow is that for every cfm in, you've got to have another cfm out, and vice versa. air conditioning unit does not turn offSo if the AC is pulling 1200 cfm from the house and putting 800 back in, it's got to find another 400 cfm somewhere. It does that, as Matt said in the video, by pulling from the garage, under the walls, through the can lights, and also down a gas water heater flue if the house has one. That last one is potentially deadly. If the air conditioner pulls air down the flue while the water heater is firing, that means the exhaust gases aren't going up the flue.

That's called backdraftingIndoor air quality problem in which potentially dangerous combustion gases escape into the house instead of going up the chimney.. It can put carbon monoxide into the house and into your lungs while you're sleeping. Not such a good idea, eh? Even if you don't backdraft a gas water heater, you're pressurizing the garage and depressurizing the house. That means all the bad stuff in that garage air wants to find a way into the house. If that's not enough for you, how about the fact that the building code doesn't allow it? Just because it's not allowed, though, doesn't mean it doesn't happen, as the video shows. Building inspectors don't catch everything. The right way to air condition a garage If you really must air condition a garage, you need to install a separate system for the garage only. The best way to do this is with a minisplit heat pump or air conditioner. It's perfect for this application because it's small, doesn't require ducts, is very energy efficient, and can be turned off when you don't need to cool that space.

Of course, another, less expensive, option would be to use window units. They'll do the same thing for less cost. You'll get more noise and lower efficiency, but if it's not used much, that's probably acceptable.As with most things, there's a right way and a wrong to air condition a garage. Then there's the question of whether you should be air conditioning it at all. So my apartment has an attached garage and I love having it, but I also live in Las Vegas where, today, it was over 100F outside. I have been considering air conditioning the garage, or even just a corner of it for a workshop with a cool breeze, but I have a little problem - since it's an apartment I can't modify the garage in any way to vent hot air outside. I've considered portable evaporative coolers, and while I've got one and it works, it only works for a little while - since the garage is so enclosed the evaporative cooler eventually humidifies the air to the point where it stops working. This also creates problems with condensation and since my hobby space in the garage is to be used for electronics, radio and various other electricity-friendly pursuits, condensing water droplets is a very bad thing.

What can I do? Is there any way to lower the temperature of the garage air without somehow venting hot air back to the outside world? Would combining an evaporative cooler and a dehumidifier work? If so, how should I arrange them for optimal cooling? Unless you can insulate, it will cost a ton of money. I get that it's a rental, but maybe the landlord won't mind if you insulate the garage. Having done that, get one of these AC units that only require you to make a 6" hole through the wall: Talk to your landlord, they may not mind these slight mods, especially if you pay for the insulation. However, if you really can't modify anything, another option is to build a smaller insulated shack in the garage, and AC that. Or, build a temporary wall to isolate part of the garage as an insulated and AC'ed space. A evaporative cooler and a dehumidifier together would likely just end up heating the garage. Consider any sort of heat pump however. The pipes can go under garage door, with just a little temporary gasket to keep it sealed.

The room-inside-the-garage idea sounds best to me, but here are a couple other crazy ideas. The basic problem is you need to push heat out of the garage. You either need a thermal barrier to keep it from coming back too fast, or you need to move out a lot of heat faster than it races back in. The room-inside-the-garage idea solves this by creating a thermal barrier between the room and the rest of the garage and pushing the heat from the room out into the garage. As an alternative, use the garage as a room inside your residence, and push the heat from the garage to the residence. Run an air conditioning unit and pipe the hot air into your main residence, where that region's AC can handle restoring a more reasonable temperature. You'd want to circulate the air throughout the apartment so that you don't end up with a hot spot right by the exhaust, and you're going to be spending a lot of money fighting against the lack of garage insulation. You could also consider insulating in such a way that you can remove the insulation when you vacate the apartment.

I'm thinking exposed batts of insulation placed against the exterior walls and particularly against the back of the garage door panels. You will doubtless need some sort of bracing to keep them up against the wall. There might be a better product for this sort of removable insulation that I don't know about, as well. Along the same lines, you might be able to get away with venting a portable AC unit outside through a small hole or holes in the wall. Patch those holes when you leave. Or maybe there's a window in the garage that you can open, fit with a wood piece the same size as the bottom half of the now open window to plug the hole, and then cut a hole in that wood piece to run the exhaust pipe to the outside. I know that this thread was a long time ago, but here is a possible solution for other people. If your garage door is the typical multi-hinged garage door that "rolls" up into the area above the garage space, you can replace one of the panels and make a hole in it to accept the exhaust tube.