Do you really have to vent a portable air conditioner outside? Air con pros share why it’s so crucial to get this step right

With the UK gripped by it's first heatwave of the year, finding effective ways of keeping cool has never been more important.

While many households will already have one of the best fans, more and more people are turning to portable air conditioners to provide the comfort they need. But it's vital you understand how these units work, and how they need to be set up, for them to be used effectively and safely.

I asked the pros whether you have to vent a portable air conditioner out of a window, why it's necessary and whether there are other options available. This is what they told me.

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Do you have to vent a portable air conditioner outside?

Yes, portable air conditioners do need to be vented outside via an exhaust hose to expel the heat that it absorbs from the room.

'Air conditioning units need to be vented, as they work by removing the heat from a room to cool it down, so need somewhere for the heat to escape to,' explains Sam Carter, heating and cooling appliances expert at Appliances Direct.

'Air cons work by pulling in warm air from the room, passing it over cold evaporator coils (filled with refrigerant) to absorb the heat, and then blowing the cooled air back into the room.' The heat that is absorbed is then expelled outside via the exhaust hose.

What happens if you don't vent a portable air conditioner?

Essentially, if you don't vent a portable air conditioner outside, it will add both hot and cold air to the room. That'll make it hotter, the cooling less effective, and it means your portable AC will have to use more energy as it works harder to cool the space.

‘If you don't vent the air cons, the hot air will sit behind the air con unit, slowing down the room cooling process & eventually causing overheating,' explains Siobhan Michael, brand director at Meaco.

What's the most common way to vent a portable air conditioner?

The most common way to vent a portable air conditioner is out of a window, and as such, most portable AC units you buy will come with a window kit. These kits help to create a seal around the exhaust hose as it's vented out of the window, keeping the cool air in and the warm air out, which ensures the portable air conditioner works most efficiently.

'A window kit is essential to use when operating a portable air conditioning unit as it will seal the exit for the exhaust hose that is redirecting the hot air (and moisture) away from the space being cooled,' explains Noel Fok, CEO and co-founder of EcoAir.

'It prevents warm outside air and the hot air being extracted from leaking into the cooled space, whilst also stopping recently cooled air escaping. Ultimately, it supports the performance and energy efficiency of the AC.

'Windows are most commonly used for portable AC heat extraction, however, you can also vent via sliding doors or rooflights using specialist seal kits similar to those provided for windows. For a more permanent solution you can also vent AC through a wall or ceiling.'

Wherever you choose to vent your portable air conditioner, it's vital that you vent it correctly. Noel adds: 'It’s important to use the equipment correctly - a badly sealed exhaust hose or a window/door left slightly open will allow a continual influx of warmer air from outside, whilst air being cooled indoors will be escaping, meaning your air conditioner will be working really hard yet you won’t be feeling the benefit as it is not being given a chance to properly cool the space.'

Can you get a portable air conditioner that doesn't need to be vented?

All portable air conditioners need to be vented outside using the exhaust hose, and in most cases this will involve using a window kit (unless you opt for a permanent solution of venting through a wall).

If you don't like the look of a window kit, another option is to opt for fitted air conditioning. With a fitted unit, you don't need to vent anything out of a window or a use a window kit. But the pay off is that you will have a permanent air conditioner mounted on your wall both inside and out.

It's worth carefully considering both your budget and your cooling needs before making the decision between fitted and portable air conditioning.

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