One of the cheapest garage cooling solutions you can use that's still effective is a simple oscillating household fan. Pedestal fans, box fans, or (even better) a higher powered shop fan will get the air in your garage moving.
It may be possible to add vents near the top of the garage door to allow heat to escape. Or you could add vent passages through the top of your garage walls, perhaps to exhaust through the eaves, if they're at the right height, or through vents mounted on the exterior siding if they're not.
Install vents or fans near the ceiling to expel hot air. Remember, hot air rises. Install a ceiling fan in the garage. Open your garage door in the evenings to allow fresh air to flow in.
Fans: The Cheap & Easy Solution
Cooling your garage is as simple as adding an inexpensive window fan. Sticking a fan in your garage's window and blowing the hot air out is an effective method to lower the temperature.
Your garage can only get as cool as the temperature outside. However, by installing one or more ceiling or sidewall exhaust fans it will help keep the temperature within reason. Exhaust fans that are placed high on the wall or ceiling, as well as directly opposite the main garage door offer the most effectiveness.
There are two main contributing factors to why your garage gets hot and steamy on a summer day, which are lack of ventilation and lack of insulation.
You'll want to position your cool air inward-blowing fans on the shadiest side of the house and the hot air outward-blowing fans on the sunny side of the house. If the sun is just pounding on the big garage door opening, adjusting the door height may help—especially if it's insulated on on the inside of the door.
Creating a cross breeze with fans is the best way to circulate cooler air and push hot air out. Find the coolest part of your house (either the coolest room or outside air from a window in the shade) and angle the fan towards the hottest part of your house.
To achieve this, the garage should ideally have two openings opposite each other – for example, air vents in the garage door and the back wall, a window or a door. This allows the air to circulate, humid air is removed, and warm air is held inside.
Cracking the door will indeed benefit and alleviate the heat that builds up. But having a well-maintained, properly insulated garage should be your top priority. In a pinch, cracking the door could make a noticeable difference, but there would need to be a cross breeze.
Infrared Heaters
These units generate heat through a low-intensity infrared tube that radiates heat throughout your garage. Infrared heaters warm objects before people, so they don't necessarily warm the air. They work well for garages that aren't sufficiently insulated because you're not losing hot air.
An uninsulated garage door is perhaps the biggest culprit for heat loss in your garage, as there is no barrier to slow the heat transfer out of your garage. In order to protect your garage from heat loss, you need a door with insulation.
If your garage is in direct sunlight, consider keeping the door closed as much as possible. On the other hand, if it is in the shade – let the fresh air in and the heat out! If you are opening the garage door, make sure you are home and not leaving it unattended.
Vents and Fans
That means installing a vent and fan in the roof where the hottest air will be can help remove the majority of the excess heat building up in your garage. Just like an attic fan, this fan can be triggered to come on when the temperature inside the garage reaches a certain point.
Installing a mini-split AC unit may well be the best way to cool a garage. While a ductless air conditioner (single-zone cooling-only unit) for your garage may be a good cooling option, if you want to be comfortable on the coldest days of winter, you should opt for a full mini-split heat pump system.
Pedestal fans, box fans, or (even better) a higher powered shop fan will get the air in your garage moving. If you have more than one fan, place them at a window or at your open garage door to blow hot air from inside your garage to the outside.
The easiest and most cost-effective way to cool a garage is to open the garage door or some windows to let hot, trapped air escape. Airflow will also help keep the air temperature cool. If possible, opening windows or doors in such a way as to create cross ventilation is most effective.
When it's 100 degrees outside chances are the inside of your garage may be 110 degrees or more. Garages are normally not insulated and therefore can become unbelievably hot during warm months.
Promote natural ventilation
One of the simplest ways to release this hot air is through a window or door. If your garage has windows, keeping these open during the day, and especially at night when the air is cooler, will prevent your garage from feeling like a convection oven.
Use a trusty 'ol fan
A ceiling fan can also help. If you have more than one fan, place one at a window or at your open garage door to blow hot air from inside your garage to the outside. Another fan can be aimed in the direction of the garage space you'll be occupying.
The best way to ventilate your garage and keep it cool is to introduce natural points of airflow through windows, vents, doors, or airbricks.
Garage whole house fans are installed in only garages that have an attic space above it. This is typically a one-story single-family home but there are two story homes that have a secondary attic above the garage.