A garage in Phoenix has a very different job from a garage in a mild climate.
Phoenix averages 111 days each year at 100°F or hotter. About 21 days normally reach 110°F or more. In 2024, the city went through 113 straight days at 100°F or higher and recorded 70 days at or above 110°F.
That much heat changes how a garage should be designed.
The roof can get much hotter than the outdoor air. A wide garage door can sit in direct sun for hours. Hot air can enter around old seals. If the garage shares walls or a ceiling with the house, some of that heat can also reach the rooms where people live.
The answer is not one special product. A better hot climate garage design comes from controlling heat at several points.
Start With Where the Sun Hits
Walk outside in the late afternoon and look at the garage.
Is the door in direct sunlight? What about the roof? Are there windows facing west? Does anything shade the garage?
This simple check can tell you a lot.
Morning sun and afternoon sun do not affect a building in the same way. West-facing garage design and windows receive strong sunlight during some of the hottest hours of the day.
A garage that faces west may need more help with shade, glass, door color, and insulation than a garage protected by the house or nearby shade.
This is also why copying a garage design from another part of the country does not always work well in Arizona. The same dark door or large area of glass can behave very differently under Phoenix summer sun.
The Roof May Be Hotter Than You Think
People often start with the garage door when trying to make a garage cooler.
Do not forget what is above you.
The U.S. Department of Energy says a traditional dark roof can reach 150°F or more during summer sun. A cool roof under the same conditions may stay more than 50°F cooler. DOE also reports that some cool roof coatings can be up to 60°F cooler than traditional black roofs.
That is a big temperature difference sitting directly above the garage.
If you are building a garage or replacing the roof anyway, lighter and more reflective roofing materials can help reduce the amount of solar heat the roof absorbs.
Insulation between the roof and garage also slows down heat moving into the space.
For garages below bedrooms or other living areas, the roof and ceiling deserve even more attention.
Radiant Heat Matters Too
Heat does not only move through hot air.
A very hot roof can also send heat downward toward the space below.
DOE says roof surfaces in hot climates can go above 160°F. Research cited by DOE found that radiant barriers reduced cooling costs by about 8% to 12% in hot climates.
Those savings refer to homes and should not be treated as a promise for one garage. Still, the research shows why controlling heat below a hot roof can help.
A radiant barrier installation is a reflective layer usually installed below the roof deck. It reduces some of the heat radiating from the hot roof toward the space underneath.
It can make the most sense when a garage shares an attic or roof system with the rest of the house.
The Garage Door Is a Large Part of the Wall
A common two-car garage door is about 16 feet wide and 7 feet tall.
That makes the door one of the biggest exposed parts of many garages.
If that entire surface faces the sun every afternoon, its design matters.
An insulated garage door can slow heat moving through the panels. Steel doors are available with several types and levels of insulation.
But do not choose a garage door by looking at insulation numbers alone.
A door has panel joints, edges, tracks, weather seals, and a large opening around it. A well-insulated panel will not solve every problem if hot air can easily enter around the sides and bottom.
The full door system matters more than one number on a product sheet.
Check the Bottom Seal
This is one of the easiest areas to overlook.
Close the garage door during daylight and stand inside.
Can you see light under the door or around the edges?
If you can see daylight, there may also be room for hot outside air, dust, and insects to enter.
The garage door weather seals along the bottom of a garage door becomes harder and more worn as it ages. Strong Arizona heat can be hard on rubber and other exposed materials.
The seals along the sides and top of the opening also deserve a look.
A door that is out of alignment can create gaps even when the weather stripping itself is still in decent shape.
If the door is not closing evenly, is leaving visible gaps, or is having problems with the tracks, rollers, springs, or opener, homeowners in the Phoenix area can have the system checked by a local company such as Glendale Garage Doors Pros.
Fixing the way the door closes can sometimes help before any larger garage upgrade begins.
Think Before Adding Large Garage Door Windows
Glass can look great on a garage door.
It can also let in more sunlight.
This is not a reason to avoid windows. It is a reason to choose them based on where the garage faces.
Small windows near the top of the door can bring daylight into the garage without turning the full door into a wall of glass.
A north-facing garage and a west-facing garage may need very different glass choices.
Tinted, frosted, and insulated glass are also available.
For a garage that gets strong afternoon sun, the amount of glass may matter more than it would in a cooler climate.
Dark Colors Can Look Great, but They Absorb More Sun
Black and dark charcoal garage doors have become popular on modern homes.
They can look very clean against white or light-colored stucco.
There is a tradeoff in strong sun.
Dark surfaces usually absorb more solar energy than lighter, more reflective surfaces. That does not mean every Arizona garage door should be white. Design still matters.
It does mean a dark west-facing door deserves more thought than a dark door that spends most of the afternoon in shade.
Look at the whole setup: direction, shade, material, insulation, and color.
The best choice may be different from house to house.
Protect the House From the Garage
For an attached garage, keeping heat out of the garage is only half the job.
You also want to slow down heat and garage air moving into the house.
ENERGY STAR calls for attached garage air sealing in certified homes to stop automobile exhaust and other garage pollutants from entering the home.
Older research shows why this boundary deserves attention.
An EPA review of homes with attached garages found that the share of household air coming from the garage varied widely between studies. Reported averages included about 9% to 18% in several homes, with much higher figures in some cases.
A separate EPA review of 16 attached-garage homes found that an average of about 11% of total house leakage came through the garage-to-house connection, though individual homes varied greatly.
Those studies were not done to measure summer cooling. They were studying air movement and pollution. But they show that a garage and house are not always as separate as they look.
Gaps around shared walls, ceilings, plumbing, wiring, and the door into the house can all create paths between the two spaces.
Do Not Treat Ventilation Like Air Conditioning
A fan can move air.
It cannot make 112°F outdoor air turn into cool air.
During the hottest part of an Arizona afternoon, pulling more outdoor air into the garage may do little for temperature.
Ventilation becomes more useful when the outdoor air is cooler than the garage or when it is being used to remove fumes and stale air.
That may mean using natural airflow later in the evening or overnight rather than trying to ventilate during the hottest hours of the day.
Shade, insulation, reflective surfaces, and air sealing are used to slow heat.
Ventilation has a different job.
Watch What You Store in the Garage
The garage may be hotter than some of the items stored inside can handle.
Paint, batteries, electronics, cleaners, adhesives, food, and other products can have storage temperature limits.
Check the label before leaving heat-sensitive products in a garage all summer.
It may make more sense to move a small group of sensitive items indoors than to cool an entire two-car garage just for storage.
The same goes for refrigerators and freezers. Appliances working in a very hot garage may have to work harder than they would in a cooler space.
Shade Can Change More Than Air Temperature
Arizona researchers have also found that shade can make outdoor spaces feel much cooler even when the actual air temperature does not fall by the same amount.
A 2025 study of hot-weather courtyards in Phoenix found shading reduced mean radiant temperature—the heat a person feels from surrounding hot surfaces and sunlight—by as much as 10°C, or about 18°F.
A garage is not a courtyard, but the lesson is useful.
Stopping direct sun before it hits a surface can be more effective than trying to deal with all that stored heat later.
Roof overhangs, trees in the right location, nearby structures, exterior shades, and the orientation of the garage can all affect how much solar heat reaches the building.
Build Around the Heat You Actually Have
There is no single garage setup that works for every Arizona home.
A shaded north-facing garage may need very little work.
A west-facing garage with a dark roof, dark door, large windows, worn seals, and a bedroom above it has a very different problem.
Start with the parts receiving the most sun.
Look at the roof. Check the garage door and seals. Look for gaps between the garage and house. Think about where glass is placed. Pay attention to what happens during the hottest part of the afternoon, not just in the morning.
Phoenix weather gives homeowners a good reason to take garage heat design seriously. With more than 100 days above 100°F in a normal year, a garage here spends a large part of the year dealing with conditions that homes in many other parts of the country rarely see.
A garage designed around those conditions does not need to feel like an air-conditioned room.
It simply needs to do a better job of keeping the sun, hot surfaces, and outdoor air from controlling the space.