How to Keep Cool With a Portable AC—Even Without a Window

by Edward Harper June 13, 2025

Many homes don’t have accessible windows for portable AC venting. But proper ventilation is essential. Without it, the portable AC will not function properly and may even heat up the space.

If you’re wondering how to vent a portable air conditioner without a window, the good news is that you have several effective alternatives. Three experts with decades of experience in AC and air ducting share their ideas.

Why You Must Vent Your AC

Ventilation is essential for portable air conditioners because they operate by removing heat from the indoor air—heat that must go somewhere, says David Rames with Midea, manufacturer of portable ACs.

"If you don’t vent it out, you’re just recycling warm air indoors," adds Martyn Fowler, of Elite Renewables. "This cancels out any cooling effect and overworks the machine."

Without venting, says Rames, hot air removed by the unit remains trapped, neutralizing the cooling effect.

Neutralization isn't even as bad as it gets, though. "Sometimes," says Rames, "a poorly vented AC can increase the overall room temperature from the heat generated by the compressor and internal components."

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5 Ways to Vent an AC Without a Window

The key is to make sure that the hot air is fully removed from the living space, says Modern PURAIR's Lane Martin. "Otherwise, your AC’s doing a whole lot of work for nothing."

There are several effective ways to vent a portable air conditioner when a window isn’t available, says David Rames. "Each of these alternatives allows the unit to expel hot air while maintaining safety and cooling performance."

Dryer Vent

Most homes already have a built-in exit hole in the siding: the dryer vent.

"You can use a dryer vent, as long as it leads outside," says Martyn Fowler. "Also, make sure that it isn't shared with the dryer, and that it's the right size."

You can install a dryer vent by yourself for about $100. The trickiest part of the project is cutting a 4-1/2-inch diameter hole in the side of the house. But this is easily done with a hole saw, a reciprocating saw, or a jigsaw.

Dedicated Wall Vent

"For more permanent setups," says David Rames of Midea, "homeowners sometimes install a dedicated wall vent with an exterior cap." Rames says that this is ideal for garages, workshops, or sunrooms.

While similar to venting through a dryer vent, it's a better option because you don't need to disconnect the dryer from its vent. Additionally, this allows you to install a dedicated wall vent near the AC unit.

Ceiling Plenum Space

In spaces with drop ceilings, you can vent the unit through a ceiling tile into a plenum space, says David Rames.

Martyn Fowler notes that this option is best suited for basements or offices, as these spaces are more likely to feature drop ceilings with ceiling tiles.

It's important to check with local fire and building codes for this option, adds Rames.

Sliding Glass Door

If you don’t have a window, Lane Martin suggests another option: using a sliding glass door.

Sliding glass doors are typically located in living rooms or other common areas where portable air conditioners are often placed.

One issue is that the tall, narrow space of an open sliding door doesn't align with the shape of an AC vent. You can get around this, though, by using a vertical venting kit or a transparent plastic insert designed for portable AC exhaust hoses.

These kits cost $35 to $50 and fit sliding doors of heights up to 90 inches.

Pet Door

A pet door in an exterior door is another way to vent a portable AC when a window is not available.

The door must lead outside, or at least into the garage. If it goes into the garage, make sure you keep the garage door open when running the AC.

Tips for Maintaining a Portable AC

Along with venting your portable AC to the outside, it's important to keep it maintained. This is simple to do by:

Cleaning the filter: Clean the AC filter once a month when it's in constant use and more frequently if you have pets.
Cleaning the AC: Clean the AC unit by vacuuming its interior and wiping down the face panel.
Adjusting its settings: Check the AC's fan settings, adjust its vents, and reset its timer, if available.

When to Call a Pro

When people install a vent through the wall, that’s considered a permanent solution and usually requires a professional to do it correctly, says Lane Martin.

Installing a dryer vent poses a similar problem. While an experienced DIYer can add an opening to a house, it's a challenge to install a dryer vent that remains perfectly weathertight.