How to Cool a Garage (Options and Advice)


How do I cool down my garage? You may be asking yourself in the blazing summer heat.

You can cool down your garage with an HVAC system, portable air conditioner, windows AC unit, mini-split system, dehumidifiers, and fans.

Maintaining an ideal temperature during any season is difficult if your garage has no insulation or is under-insulated.

Let’s look at why your garage is so hot and how to cool it down.

Should I Air Condition My Garage?

Consider how much and how you use the garage space. If your usage is low and you don’t spend a lot of time in your garage

Then maybe fans could be a good option. If you need to get space colder only sometimes, then windows AC could be a good option.

On the other hand, if you spend a lot of time in your garage doing work, projects, gym, or game room. You’ll want to maybe invest in a more permanent way to keep the hot air in the bay.

Also, if you store valuables that are sensitive to temperature changes and humidity. You should consider a garage air condition system.

If you have a room above or surrounding the garage. Cooling your garage helps keep the adjacent rooms cooler.

My Garage Is Too Hot

Garages are often too warm because:

Under-Insulation or No Insulation

  • Insulation helps keep your garage warm and cool. Insulation isn’t just for keeping the heat in over the winter — it also keeps heat from the sun out in the summer.

No Ventilation or Windows

  • A garage without ventilation or sufficient airflow will heat up fast.
  • Garages usually have 1 or 2 windows or not at all.
  • If your garage has windows, consider keeping them open to create ventilation or covering windows with curtains or sun-blocking film.

Garage/House Orientation and Location

  • If your house and garage face to the south or west. They will heat up during the afternoon sun. Also, depending on your region, how the sun angles your location.
  • Early mornings up until around 10-11 a.m is the best time to use your garage if you don’t have any air conditioning.
  • 3-6 p.m. It is usually the hottest time during the day.

Garage Colors

  • Garage door and roof colors. Dark colors absorb more heat than lighter colors.

High Humidity

  • High humidity traps heat and makes the air feel hotter than it actually is. Lowering the humidity will help make it more comfortable.

Garage Usage

  • If you park your car with a hot engine in the garage. The heat will radiate from a vehicle for a long time. The garage will heat up very fast.
  • Park your car outside in the shade or wait for sunset before driving it to the garage.

Too Much Stuff in the Garage

  • If you have loads of objects, clutter, and stacked boxes in your garage, they obstruct the proper airflow. Clutter in the garage also limits your ability to use your garage’s full capabilities.
  • Clean up and de-clutter the space. Adding helpful storage systems and cabinets and overhead storage will keep your garage nice and tidy, and the air flows much more straightforward.

Garage Cooling Solutions

HVAC (Heating, Ventilation, and Air Conditioning)

It is just like your home’s central air condition system.

You could install a separate HVAC system for your garage. But it’s costly after initial construction.

If your garage is attached to your home HVAC system. It’s unlikely there are many air ducts or return vents in the garage. It’s common too for garages not to be looped into your home HVAC.

You should not use your home system to cool the attached garage. If it’s not designed to do so. The large air volume in the garage that needs to be cooled will put a massive strain on your central air system. 

The garage also has pollutants like carbon monoxide from your car.

LINK to building America solutions center for more info.

Air Source Heat Pumps / Mini Split Air Conditioner

Mini-split systems have 2 parts. Small wall-mounted air condition unit which can warm the space also and outside compressor unit. Much like the central AC unit on your house but on a smaller scale.

Only power and refrigerant lines run through the wall, making the installation fast and units easy to position optimal places inside and outside walls even far away from each other.

Some models offer four modes of operation: cooling, heating, dehumidification, and ventilation.

About mini-split systems, The name is a take-off on standard split system AC and heat pump systems. The equipment is smaller, and, most importantly, no ductwork is required.

Your garage/house can also have 1-3 inside units.

Mini-splits are more expensive than windows AC units and need to be installed by HVAC professionals usually. Some models offer DIY installation.

Windows AC units

Standard windows AC unit can be a good choice for a garage, especially if your garage has windows. Consider the larger air space of the garage when purchasing a unit.

You can install a windows AC unit to the wall or hire an expert to do the job.

Window AC units are cheap and effective.

Dehumidifiers

High humidity traps heat and makes the air feel hotter than it actually is.

If you live in a region with high humidity. Lowering the humidity of the air will help make it more comfortable.

It can feel 5 to 10C or 10F degrees cooler because the relative humidity is reduced.

If you want to store sensitive items in your garage, you should lower the humidity to avoid mildew, rust, and other moisture and condensation-related problems.

Dehumidifiers don’t blow cold air like an AC unit. So you can combine a dehumidifier with other cooling options.

Dehumidifiers are cost-effective and portable.

Fans

Consider a ceiling fan if you have the space for it and your garage door opener is not in the way. There are, of course, portable versions. Exhaust fans can also be installed in a window or through the wall.

Get an industrial-strength fan with stronger blades instead of a residential version if you do woodworking or other work in your garage that creates sawdust or other debris in the air.

Fans also have the added benefit of sucking any fumes out of your garage. Exhaust from a car or like any solvents or paints you might be using.

Fans are cheap as both permanent installation or portable variety.

Portable Air Conditioners

Portable air coolers can cool a small to medium space depending on the unit’s efficiency. The garage has a large air volume, and a portable unit may not be enough during hotter days.

Portable units take up floor space and also need to be vented to the outside air.

If you don’t have windows in your garage, then you need a hole in the wall. If you know how to operate reciprocating, saw it’s a quick job, or you can hire an expert to install an exhaust vent.

Most portable air conditioning systems come with a hose and adapter to vent to the outdoors.

Will Portable AC Cool a Garage?

Portable units are not recommended for a garage.

If you must use one. Consider a Commercial-Sized portable A/C Unit.

How to Cool a Garage With No Windows

  • If your garage doesn’t have windows or proper ventilation creating a cross-breeze is harder.
  • Park your car outside to cool down or wait for sunset before driving it to the garage.
  • Work on your DIY or projects outside if possible.
  • Replace your garage lights with LED. Incandescent light bulbs produce heat.
  • Place fans around the garage to provide airflow.
  • Buy a portable AC unit. Use it during the hottest months or just before using the garage.
  • Install windows AC unit through the wall or mini-split system.
  • Install vents to the attic and roof.
  • Install vents to the garage door.

How to Ventilate Your Garage

Improving garage ventilation will help draw cooler air in and push the hot air out.

Installing vents to the attic and other vents in the garage door or walls can help most of the heat escape through your garage attic. This creates airflow to cool the garage with passive convection as cool air moves from the ground upwards and forces the hot air out.

Passive ventilation is typically installed on the roof in the form of spinning turbine vents.

Active ventilation methods include fans in the roof and walls.

Where Should Fans Be Placed in a Garage?

If the outside air is hotter, then blow the air out of the garage.

During the evening, reverse the airflow to draw cooler air outside to inside your garage. If you have a smaller service door, you can use that also to draw the air in.

Bring cool air in and force hotter air out.

What Size Air Conditioner Do I Need for My Garage?

Air conditioners are rated as BTUs. Which describes how much heat can be removed from a closed space, among other things. Sometimes the AC size is referred to as “tons,” which is the equivalent of 12,000 BTUs

First, measure the size of your garage. by multiplying the length by the width.

For example,

Two-car garages are usually 20×20 feet, so it comes to 400 sq. ft. Now multiply 400 sq. ft by 25 BTUs which comes to 10,000 BTUs

The resulting number is the BTU capacity required.

According to Energy Star, space like 400 sq. ft requires 9,000-10,000 BTU air conditioner.

There are also calculators like this online. But those are only estimations.

Your garage may get more sun or shade, which should be considered when buying a unit. Climate, ceiling height, and insulation also play a role.

  • If your garage gets a lot of sun, increase capacity by 10%
  • If your garage is heavily shaded, reduce capacity by 10%
  • Add 2,000 to 4,0000 BTUs if the garage is uninsulated.
  • Add 1,000 to 2,000 BTUs if your garage faces south and/or west.
  • Add 1,000 BTUs if your climate is very sunny rather than cloudy.
  • Add 1,000 to 2,000 BTUs if your garage is in a very humid climate like the South, Southeast, or Northeast.

A properly sized AC rewards you with energy savings. Consult an AC expert if you are unsure how to size the air conditioner.

How Hot Garages Get in Summer?

On a hot summer day temperature inside a garage can be 10-18° F or 5-10 C Higher than outside.

Should I Leave My Garage Door Open in Summer?

Of course, keeping the door open lowers the temperature if you don’t have insulation or any kind of air conditioning system in your garage.

Keep the door open Only if you are home and/or in the garage and there is nothing valuable in your garage. But considering you have tools, lawn equipment, sports gear, and bicycles—no reason to offer easy picking to thieves.

Don’t leave your garage open and unattended if you plan to leave your home.

How Much Different Cooling Solutions Costs?

Central system: between $3,500 and $8,900. Uses duct system that’s usually combined with the heating system

Ductless split systems: $1,000-$5000 installed. as mini-split (ductless) that are installed as inside and outside units

Window air conditioners cost $150-$700 installed. Added in windows as a singular AC system

Portable units: prices vary but align closely with the cost of window units. They come as a split, hose, or evaporative system for ease of movement around the house.

How Do I Cool My Garage Cheaply?

The most cost-effective and easiest way to allow hot trapped air to escape is by opening the garage door or entry door if you have one and windows to create a cross-breeze. The airflow will keep the garage a little bit cooler.

Also, you can install fans.

If you want cheap cold air. Build a “Swamp cooler” with a bucket of ice with a fan blowing across it. Or cut 2 holes in the bucket side and put the fan blowing towards the ice from above.

Garage Air Quality

At least you should have some ventilation to get air moving out of your garage. Considering all the chemicals, oil, paint, pesticides, harsh cleaning supplies, and other similar things you might store in your garage.

There are also pollutants like your car exhaust emitting dangerous carbon monoxide.

You should install an exhaust fan at least. Ventilating your garage helps fumes dissipate, keeping your family and pets safe.

Particle Pollution

If you use your garage as a workshop, you may produce large amounts of wood dust, metal shavings, metal dust, and paint particles. These should be filtered with a robust mechanical filtration system.

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