Do You Have to Vent a Portable Air Conditioner?

You've bought a portable air conditioner and want to see how it works. To your surprise, while the AC is blowing cold air, the room seems to be getting warmer. Then you realize there was a venting kit with a window adapter supplied in the box.

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To get the unit to work properly, you must vent your portable air conditioner.

How Does a Portable Air Conditioner Work?

A portable air conditioning unit works like a standard air conditioner. Warm air in the room is drawn by a fan over an evaporator coil that’s filled with refrigerant gas at a very low temperature. This process cools the air in the room and, at the same time, the refrigerant heats up from contact with warm air.

The warmed refrigerant gas goes to a compressor that pumps it up to a high pressure. The hot compressed gas then passes to a condenser coil at the back of the AC. The refrigerant gas is now hotter than the air blown over the condenser by the condenser fan. As the refrigerant gas passes through the condenser, it cools and condenses back to a liquid, transferring its heat through the portable air conditioning vents.

The refrigerant, now in liquid form, passes through a special expansion valve where it's allowed to rapidly expand. As the refrigerant expands, it cools and becomes very cold. This cold refrigerant gas goes back into the evaporator to repeat the AC cycle.

Do Portable AC Units Need to Be Vented Outside?

Experts say they do. If you didn't have a portable air conditioner exhaust hose to vent the hot air, the heat from the condenser would stay in the room. This negates the cooling effect of the air conditioner, and the room gets hotter because of the energy needed to power the compressor.

So, the purpose of the vent hose is to blow the hot air from the portable air conditioner to the outside and allow the unit to cool the room.

Is Portable Air Conditioner Exhaust Harmful?

According to Ducting.com, the exhaust that comes from a portable air conditioner unit isn't harmful. Even though it's called "exhaust," it contains only hot air and moisture. There's no risk of carbon monoxide poisoning from a portable air conditioner.

Portable Air Conditioner Venting Options

There are many options for venting the heat from a portable air conditioner. These include:

Window Vents

You can exhaust the hot air from the portable AC through a partially open window using a window vent kit. There are models designed to fit different windows, but they all work in the same way: A baffle made from plastic or other material fits into the open window space and seals the window. The baffle has a hole you fit the vent hose into to exhaust the hot air outside.

Sliding Door Vents

This type of kit has an extendable baffle that seals a partially opened sliding door. The kit is usually made from a plastic material and has a hole for the vent hose in the bottom section.

Can You Use a Portable AC in a Room Without a Window?

Wall Venting Kits

A versatile solution that works with most walls, these kits include a flexible pipe that’s passed through a suitably sized hole in the wall with a plastic adapter for fitting the vent hose. Some types include an insect screen, while most have a plastic cap to seal the opening when not in use.

Ceiling Venting Kits

Intended for drop ceilings, this kit replaces a ceiling tile and vents the portable AC's exhaust air into a ceiling cavity. Some include an extension vent hose for easy connection to the portable air conditioner.

Dryer Venting

These use an adapter to fit the portable AC's exhaust hose to a dryer vent.

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Ventless Air Conditioners

A ventless air conditioner is an evaporative cooler, sometimes known as a swamp cooler. It has a pump that squeezes water through small nozzles. As the water expands, it vaporizes. The rapid expansion of the water from a liquid to a vapor, known as adiabatic cooling, chills the water. Ventless air conditioners work best in dry climates that promote evaporation.

Other truly ventless options include window units and mini-split air conditioners, though they cost more and are more expensive to install than portable AC units. Dehumidifiers can remove hot, moist air from a room, which can make it feel cooler. Many models don't require venting, and keep water removed from the air in a reservoir instead. Keep in mind, however, that dehumidifiers aren't meant for cooling.

While you may see certain portable AC units advertised as "ventless air conditioners," it's really buyer beware. Most of these are actually evaporative coolers or "cooling fans" in disguise.

As discussed, most portable air conditioner models that use refrigerant as a means of conditioning the air generate heat. Where there's heat, there's also water vapor. If you live in a humid environment, you want these things expelled from your home, which is the reason for portable air conditioner vents in the first place.