How to Air Condition a Garage

Most people do not concern themselves about cooling a garage in summer. However, whether you use your garage as a workshop or a hangout, you may decide that you want to make your garage more comfortable. If you use your garage space as a workshop to work on cars or home maintenance projects, a garage can be a pretty unpleasant place to work in during the scorching Southern California summer if it is not cooled.

If you keep a refrigerator or freezer running in your garage, there are also practical reasons for adding air conditioning. Without it, these appliances may overheat when running on hot days. You have several options for cooling a hot garage, depending on your local conditions.

If your particular area is blessed with more mild summers, you can probably get away with an exhaust fan that provides large air changes throughout the day. However, if your summers are hot like most of California, you may need an actual window air conditioning unit.


Here is what you need to know to air condition a garage.


Benefits to Air Conditioning the Garage

Depending on what you use your garage for, installing an air conditioner may be a wise move. Not only will adding air conditioning to your garage make it a more pleasant place in the summer, but it can also help with your home air conditioning expenses since a cool garage helps keep the rooms surrounding the garage cooler. In the same way that insulation keeps warm air from permeating your house, the pocket of air inside your garage can help slow the absorption of outdoor heat into the home. In an un-cooled garage, hot air slowly can worm its way into your home through a shared wall or door, raising indoor temperatures and forcing your air conditioner to work harder.

Additionally, if you use your garage to store things of value, such as a classic car or musical instruments, keeping your garage temperature controlled can help ensure your belongings are not ruined by things such as rot and other damage. If you use your garage as a workshop, keeping your workspace temperature controlled is even more appealing since it will provide a more comfortable place to do your projects.

Even if you only use your space to store basic items like paint and other household goods, keeping it cool is still a good thing to do. Lumber can warp in extremely high temperatures and humidity. Extreme heat can also affect the quality of paints and varnishes.


Caution Regarding Central Air Conditioning

An air conditioner will not supply sufficient fresh air to negate the effects of solvent fumes, carbon monoxide or other toxic gasses or fumes.

For this reason, you should NEVER tap into the house air conditioning system to cool your garage. While extending your home’s central air conditioning into a garage by adding a length of ductwork through the side of the home and into the garage, might seem like a logical solution on paper, this can be very dangerous.

Your garage typically will not have an air return back into the HVAC system, and when a central air duct is extended into a garage, it can create abnormal pressurization in the garage. This forces the rest of the home to become slightly depressurized because the air in the garage cannot get back to the air return. While this change in pressure cannot be directly felt, it poses problems. Negative pressure in your home has to be relieved somehow, and what usually happens is that your home will draw air in from outside. Outdoor air bypasses the HVAC filter system, allowing pollutants and allergens to build up inside. And it also makes it harder to keep your home cool, since there is a constant flow of warm air coming in from outdoors.

And never forget the health consequences to tying the whole house air conditioner to the garage. This is potentially dangerous as fumes can enter your home via the ductwork. Whether you are just warming up the car or painting a bookshelf, a large number of fumes are present in your garage at any given time. Some of them smell odd, but others, like carbon monoxide from the exhaust, can be deadly.


Sizing Garage Air Conditioners

Adding a simple space air conditioner to the garage is by far the best solution for cooling the space, but determining the proper size is critical. Many people add air conditioners to their garages and are disappointed when they discover that they do not cool properly. This happen because the homeowner does not know how to size their units. Any ductless air conditioner, be it a window unit or a portable unit, is only capable of cooling a certain amount of space based on its design.

Air conditioners are rated in units called BTUs (British Thermal Units), which describe how much heat can be removed from a closed space. Determining the proper air conditioner size starts with measuring the size of your garage.


How to Air Condition a Garage

  • Add Insulation

Keeping your garage cool starts with proper insulation and the area that requires the most attention is the garage door. It is important to purchase insulation that is compatible with the type of door you have. Here is a general overview of the types of insulation that work best with certain kinds of doors:

  • Steel Garage Doors – Compatible with any type of insulation.
  • Wood Garage Doors – Rigid insulation works best for wooden garage doors.
  • Flat Garage Doors – Garage doors without panels work best with reflective insulation or foam board.


In addition to the garage door, you will also want to make sure any windows in your garage are insulated. Window film can do a great job of significantly reducing the amount of heat that enters your home. You can also add blackout curtains for additional insulation.


  • Choosing the air conditioner

Your easiest options include using a window unit or a portable unit. A ductless mini-split system or adding a connection to your central air is possible, but these options require more labor and professional HVAC knowledge and may not be cost-effective. Choose an Energy Star certified air conditioner for the most energy efficiency.


  • Adding a window unit

Most garages have a window already installed. But if your garage does not have a window, you will need to create one in order to install a window A/C. In a windowless garage, consider using a portable air conditioner, which requires a smaller access hole for ventilation.

  • Measure the window to make sure it will accommodate a window unit.
  • Install all included mounting hardware.
  • Lower the window sash and secure the unit.
  • Close all gaps around the unit using fireproof weather-stripping or removable caulk.


Give Us a Call

Heating and cooling your garage just got easier, with help from Aire-Tech! We give you countless resources to help you explore and learn about HVAC options for garages and workshops. To tackle your home’s indoor comfort challenges head-on, do not hesitate to reach out to us by phone or through our website.


If your system needs repair or inspection, call Aire-Tech on 951-926-1002. You can also visit our Contact page and complete the contact form.