How Do You Actually Cool a Garage in Phoenix?

Why does a garage get so much hotter than the rest of the house?

A garage is the one room the builder never intended to condition: uninsulated or barely insulated walls, a big steel door that soaks up afternoon sun, no supply vents, and — in most Valley tract homes — a west or south orientation that catches peak heat. Add the thermal mass of the slab and the cars themselves radiating engine or battery heat after every drive, and the garage holds its heat well into the night.

EV ownership raises the stakes. Level 2 charging generates real heat — in the car's onboard electronics and battery management, working hardest exactly when the garage is hottest — and lithium batteries prefer to charge cool. That's why EV-charger garages have become our most common garage mini-split install: Waddell and New River shop garages, Peoria and Surprise EV households, Anthem three-car bays turned gyms.

One thing you should never do: cut a supply vent from the house system into the garage. Residential code prohibits it for a reason — the duct connection can pull car exhaust, fuel vapors, and stored-chemical fumes into the living space, and the added load unbalances a system that was never sized for it.