How to Cool A Garage With No Windows: 8 Simple Tips

Researched & Written by Craig

Some windowless garages can become absolutely unusable in summer.

Sweltering heat, hot and sticky air… we basically end up with a no-go zone inside our own home! Thankfully, there are a few ways we can tackle these hot boxes. In short:

Keep your windowless garage cool by installing insulation where possible, using fans, swamp coolers and portable, mini-split, or window air conditioners. Repaint any dark colors, and keep the door closed if in direct sunlight. Don’t park hot cars inside, and dehumidify if it’s too humid.

But there’s more to it than that. Read on for our full run-down of tips.

Tips for Cooling a Windowless Garage

To Open or Not Open The Door…

One simple question is whether to open your garage door or not. Will having it closed trap in more heat? Or will opening it just bring in even warmer air?

The answer relies on the sun. If your garage is in the shade, then you’re probably better off with an open door. The surrounding air should be comfortable enough that you want it to come in.

If you’re in direct sunlight however, you need to go to war with the sun. That’s when you should try to block out all temperatures from the outside, and create a haven of coolness within your garage. This is mainly done through insulating against the outdoor temperature, and actively cooling your indoor space.

Improve Insulation

As daunting as it can be, beefing up your insulation is the best way to help fight back against a hot summer (or a cold winter).

What? I thought insulation was just to keep heat in! Won’t it make my garage warmer?

No, don’t worry. Insulation acts as a barrier between your home and the outdoors. It helps seperate the temperatures and make it much harder for the outdoors to influence your home. No matter if that’s hotter or cooler.

Insulation helps keep your temperature steady. [Source]

I know that insulating can seem like a huge hassle. You’d need to hire a contractor, and that would cost hundreds or thousands! Right? Thankfully, it’s not the case. Especially for a garage.

You can pick up extra insulation for under $20, and have it installed yourself by the end of the day. In a garage that isn’t exactly designer, it’s okay to only do a rough job. It’s not your living room! There’s plenty of guides online for this. But if you want some more info, check out our guide to handling an uninsulated basement.

Use Powerful Fans/Swamp Coolers

While a shoddy old fan might not make much difference, modern pedestal fans pack some serious punch. A powerful oscillating fan can help cool a working area for you, and a Vornado fan can even ‘bounce’ that airflow around your whole garage.

Equally, a swamp cooler can be a cheap version of an air conditioner. Bonus points if you add ice to it, giving your cooler air than most air conditioner can produce! If you’re only working with a normal fan, placing a bucket of ice infront of them can give you a ‘DIY’ air conditioner. Every little helps!

To make the most of your fans and coolers, use them with the garage door closed (though maybe with any connecting doors to your home open). You want to encourage the air to flow around your garage, not out of it!

Encourage Airflow From House

If your home’s got a good cooling system, and it’s connected to your garage, consider trying to ventilate that cool air into the garage.

Setting up a powerful garage fan or two can massively improve airflow and ventilation into your garage. By directing your cool home air into the garage, it does make your home slightly warmer but can be the difference between a bearable or unbearable garage temperature.

Pick Up an Air Conditioner

Many central AC systems don’t extend to our garages. Which is a massive pain when we need to use them!

Thankfully, there are a few efficient one-room options to consider. Obviously these are a little more expensive than $10 foam insulation, but they can be worth it if you’re going to spending a lot of time over summer.

  • Portable Air Conditioners. The most basic option, these aren’t the most efficient but are simplest to set-up. The only issue is they need somewhere to exhaust through – either a pre-installed exhaust point in the wall, or potentially back into your home. A last-ditch effort for a windowless garage would be to open the door slightly, and – aside from the AC exhaust – block off the area under the door with something like sandbags or insulation filled boxes.
  • Mini Split Air Conditioners. Super simple, these aren’t cheap but they work exceptionally well. The cooling part of the AC sits indoor, connected to an outside exhaust via a small pipe drilled through the wall. A technician can get one installed within an hour or two for you. See more in our mini-split guide here.
  • Window Wall Air Conditioner. Window air conditioners? But I don’t have a window!! – Don’t worry. Many quiet window ac models can actually be mounted into the wall. It takes some commitment (and creating a hole in your wall), but the process is fairly simple and a contractor can have one installed within a day.

Repaint Dark Colors

If you don’t wear black on hot days, why should your garage?

Having dark walls or a dark roof is a recipe for an absolute hotbox of a garage. Repainting these white (or a light color) can make a massive difference in the amount of heat that’s absorbed into your space. Just be aware the opposite is also true – a darker garage will stay warmer in winter by taking in more heat. (Though I wouldn’t recommend repainting it every 6 months!)

A quick repaint can be done over a spring weekend, and help keep indoor temperatures down by a few degrees.

Wait Before Parking Inside

Cars run on fire and explosions.

No, I’m serious. Your engine gets HOT when it’s in use. Especially on a hot day. ESPECIALLY if you’ve been driving around in the sun.

Although the AC in your car may keep the inside cool, don’t forget that the vehicle itself is very warm. Putting that straight into an enclosed space is only going to heat that space up.

If you’ve driven back home on a hot day, consider leaving the car outside of your garage to avoid heating it up. Let the engine cool off (and ideally wait for shade) if need your garage at a cooler temperature.

Use a Dehumidifier

The humidity in your air can completely change how a temperature feels.

High humidity can ake things feel stuffy, sweaty, and just a nightmare to be in. On the other hand, lower humidity can make things much more comfortable – especially for manual work. A simple dehumidifier can help turn this around. Just make sure your garage is enclosed – or you’ll be trying to dehumidify the world!

Install Attic Vents

If your garage is frequently hotter than the outside temperature, the most important tool you have is ventilation. Getting rid of that hot air so cooler air can come in.

If that’s the case, consider installing vents in your attic/garage roof. These can be opened to let the indoor air ventilate out, and closed if your indoor temperature is preferable to the outside one.

This is especially true for heat – which always rises up. Having attic vents can help it to escape, leaving you cooler and more comfortable.

Conclusion

A windowless garage can become almost unusable in the summer heat.

Hopefully, these tips have given you some ideas in how to keep your garage usable all year round. While each may not be a huge game-changer, combining a few of them can quickly bring your garage back into a usable temperature again.

If this guide’s helped you, please consider checking out our related articles below. We’re entirely reader-supported, and gratefully appreciate any time you spend browsing this blog.

Thanks for reading, and have a great day!

-Craig