Temperatures of over 100º F occur regularly in Florida garages every summer, and they are caused by three factors that all converge each hot afternoon. First, a garage is not a conditioned living space, so it is not required to have insulation in the walls or above the ceiling. So most homebuilders don't do it. Then there's the sun on the exterior walls of the garage radiating heat into it, and the heat trapped in the attic radiating downward. Add to that the lack of any installed ventilation system, sometimes not even a window, and you have the recipe for a hotbox. But there are several tactics you can use to cool it down.

Garage Screen Door - They come in sliding panels, motorized on an overhead track, and inexpensive lightweight removeable panels. Any style you choose provides plenty of passive ventilation to let the heat out. 

Ceiling Exhaust Fan - The drywall ceiling of a garage is a fire barrier between the attached garage and the living area of your home. It is required by code to be continuous, without any openings. But we often see an attic access hatch cover in the garage with a screened opening cut into it, or propped open a little with a block of wood, to let the hot garage air vent into the attic and out the roof vents. This works, but it allows any fire that starts in the garage—which is statistically where many home fires start—to move quickly into the attic and race across the top of the the home.
    One way to get garage ventilation without sacrificing fire safety is the GF-14 garage exhaust fan, manufactured by America’s Best Home Products (www.coolmygarage.com). The damper at the top of it, shown below, has a fusible link that automatically closes it when the temperature reaches about 200º F.

Air Conditioning - Because of that same fire safety issue, you cannot just add a supply duct or two in the garage from the house a/c system to cool the garage down. But you can install a mini-split heat pump system or window air conditioner that just serves just the garage.

Heat Pump Water Heater - How does free air conditioning sound? A heat pump water heater takes in hot air, transfers the heat to the the water heater tank, and then exhausts cool air back out. They are more expensive to buy than a regular electric water heater, but use less energy and, if installed in the garage, will make it noticeably cooler. See our article What is a heat pump water heater? for more details.

Insulation - Adding insulation helps buffer the garage from outside heat, and is definitely necessary if you plan to air condition your garage. A layer of insulation in the attic over the garage is easy to do, but it is likely that your garage walls have no insulation. Adding it there is more complicated, especially if you have concrete block exterior walls. And, of course, insulating the garage door is necessary to do it right. 

• • • • • • • • • • • • • • • • • • • • • • • • • • • 

Here’s links to some of our other blog posts about GARAGES AND CARPORTS:

• Why is a garage floor sloped?  

• What is the difference between a carport and a garage? 

• Why is my garage ceiling sagging? 

• Why are there score line grooves in the concrete floor of the garage? 

• What are the common problems when a homeowner converts a garage to conditioned living space, such as a family room?
 
 • What are the code requirements for fire separation between an attached garage and the house?

• Can a bedroom door open into the garage?

• Does an attached garage that is only used for storage or as a workshop, and not for parking a car, still have to comply with building code requirements for a garage?

• How far apart should electric receptacle outlets be placed in a garage?  

• What is the raised metal plate on the floor under the garage door?

• Why do I have to hold down the button to close the garage door? 

• How can I check my garage door to make sure it is safe?  

• What does a home inspector check on an electric garage door? 

• Can the a garage door header bracket and torsion springs be mounted through drywall? 

• How can I tell if cracks in the garage floor are a problem or not? 

• Is tempered/safety glass required by the building code for windows and doors? 

• Why can't I use my home's central air conditioning system to cool the garage? 

• What is the unusual garage door opener mounted on the wall above the door and marked "Wayne Dalton”?

• When were GFCI receptacle outlets first required in the garage?

• Why are most pull-down attic ladders not approved by building code for installation in a garage? 

• Is the wood anchor pad for a garage door rail and torsion spring supposed to be nailed or bolted to the wall? 

• Is a ceiling receptacle outlet for a garage door opener required to be GFCI protected? 

• What is the minimum slope for a garage floor slab?

• Can you run exposed NM-cable (Romex) in a garage?  

• What causes a garage floor to crack?

• What is the difference between an attached and detached garage? 

• What is code for the fire rating for garage walls?

• What is code for the fire rating for a garage ceiling? 

• What is code for air conditioning a garage?

• Can I use plywood between garage and living space of my house? 

• Is an attached garage required to have a door to the house or exterior?

     Visit our GARAGES AND CARPORTS page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.