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FAQ

Questions and answers

Lower the room temperature or simply circulate the air?

If you actually want to lower the room temperature, the difference between the indoor and outdoor temperature is crucial. If it is consistently cooler outside than inside, an open window and a fan can help to move the warm air outwards and make the indoor air more comfortable.

However, if the outdoor temperature is equal to or higher than the indoor temperature, a fan will only circulate the air without actively cooling it. In this case, you will need an air conditioning unit. This also applies if you are unable to leave the window open for extended periods, or if you wish to achieve a noticeable reduction in room temperature – for example, of at least 2 °C.

No, a fan alone does not reduce relative humidity sufficiently. It merely circulates the room air. If humidity needs to be reduced significantly – for example, from 75% to 55% – an air conditioning unit is the appropriate solution, as it lowers the room temperature and removes moisture from the air during the cooling process.

Which air conditioning unit is appropriate and what output it should deliver depends on several factors. Of primary importance is the room size, either as a floor area in square metres or, more precisely, as a room volume in cubic metres. The larger the room, the more air needs to be circulated and cooled.

Equally important is the heat load. This includes, for example, solar radiation, large window areas, poorly insulated rooms, technical equipment, people present in the room, or warm air entering from outside. In addition, the desired cooling time plays a role: if a room needs to be cooled down very quickly, a higher cooling output and air circulation capacity will be required than for a slow, gradual reduction in temperature.

To determine the appropriate cooling requirement, you should first clarify what objective you wish to achieve. Is the aim to noticeably lower the room temperature, and if so, by how many degrees Celsius? Or is the primary focus the reduction of humidity?

It is helpful to divide your house, flat, or business premises into individual rooms or zones. This makes it easier to assess which areas should be cooled first and whether there are specific sections within a room that are particularly affected by heat.

Also take note of potential heat sources. These include, for example, solar radiation, large window areas, electronic equipment, machinery, people present in the room, or warm air entering from outside. It is also important to consider whether these conditions are likely to change over the coming days – for instance, due to a change in weather, increased use of the room, or additional equipment.
Yes, though often not immediately. Rooms, walls, floors, and furniture store heat over extended periods. This stored heat is frequently perceived as latent heat or heat build-up. As a result, a room can remain warm even after the outdoor temperature has already dropped.

If the outdoor temperature drops for several days and you are able to keep the windows open for extended periods, the stored heat can gradually be dissipated from the room. The key factor here is that a sufficient flow of cool air enters. If the cool airflow is stronger than the heat stored within the building, the room can cool down again over time.
Latent heat can remain stored within a building for several days. Walls, floors, ceilings, window surfaces, and furniture absorb heat and release it only gradually. This effect can be imagined in a similar way to a sponge: the building stores the heat and releases it back into the room air only little by little.

How quickly heat build-up dissipates depends on various factors. These include, amongst others, the building materials used, the intensity of solar radiation, the outdoor temperature, the available ventilation options, and the volume of fresh, cool air entering the room. In residential spaces, it can take approximately 5 to 10 days, depending on the situation, before the stored heat is noticeably reduced.
The air changes per hour figure indicates how many times the air in a room is completely circulated or replaced within one hour. This value is important for assessing the output that an air conditioning unit or air blower must deliver. The larger the room or room volume in m³, the more air needs to be moved.
In addition, the temperature difference between the current and desired room temperature, the existing heat load, the humidity, and the desired cooling time all play an important role. If a room needs to be cooled down quickly, or if heat is continuously being generated, a higher air change rate is required.
How many air changes per hour are appropriate depends on the room size, heat load, usage, and desired target temperature. As a general guideline: the more intensely a room heats up and the more quickly the desired temperature needs to be reached, the higher the air change rate should be.
A 2-fold air change rate per hour is generally the minimum. It is suitable for rooms with a low heat load where the desired temperature differs only slightly from the current room temperature. Typical examples include storage rooms with little activity or wine cellars.
A 4-fold air change rate per hour is appropriate when there is an additional heat load from outside or stored heat within the room. This applies, for example, when several people are present in the room, when equipment or machinery is generating heat, or when goods are brought in that are warmer than the desired room temperature. For temporary air conditioning – such as in office spaces – this value is often a good standard.
An 8-fold air change rate per hour is recommended when the target temperature must remain as constant as possible and higher heat loads are present. This may be the case, for example, in food storage facilities, laboratories, or other sensitive environments.
A 16-fold air change rate per hour or more is required when very high or strongly fluctuating heat loads are present and the target temperature must be reached within a short period of time. Examples include areas with sensitive electronics, vehicles, technical testing environments, or research laboratories.
A monoblock air conditioning unit consists of a single compact unit that is placed directly in the room. The unit draws in warm room air, cools it, and returns the cooled air back into the room. The warm exhaust air produced in the process is discharged to the outside via an exhaust hose, typically through a window or another opening. To prevent as much warm outside air as possible from re-entering the room, a flexible window seal is generally recommended.
A split-type unit, on the other hand, consists of two parts: an indoor unit inside the room and an outdoor unit, known as the condenser. The indoor unit cools the air in the room, whilst the heat generated is transported via thinner pipes to the outdoor unit, where it is discharged. As a result, split-type units generally require smaller openings to the outside than monoblock units, and the waste heat can be dissipated more efficiently.
The main practical difference lies in how they are used. A monoblock unit does not require a separate outdoor unit and is therefore easier to install. A split system is often more efficient, but requires a suitable location for the outdoor unit, such as on a balcony or in front of a window. If the window needs to be closed completely, the split system usually has to be disconnected first.
Which portable air conditioner is best suited depends primarily on the layout of the room. If the room has a window that can be opened or tilted, a monoblock air conditioner is often the simplest and most flexible solution. The warm exhaust air is channelled outside via a hose, whilst the unit itself is placed inside the room.
A monoblock unit is particularly handy if windows or doors need to be closed from time to time, or if there is no suitable space for an outdoor unit. This makes the unit easy to use and allows it to be moved to other rooms if necessary.
If, on the other hand, you have a suitable place to install the outdoor unit safely – for example, on a balcony, a terrace or in front of a suitable window – a portable split-type air conditioner may be the better choice. Split-type air conditioners dissipate heat more efficiently and usually require smaller openings than monoblock units.
Yes, we generally recommend using a flexible window seal. This prevents warm outside air from flowing freely back into the cooled room through the open window. As a result, the air conditioner can operate more efficiently and maintain the desired room temperature more effectively.
Window sealing offers several advantages:
  • Greater efficiency: The amount of warm air entering from outside is significantly reduced, meaning the air conditioner needs to use less energy.
  • Improved cooling performance: the cool air stays in the room for longer and the temperature can be maintained more consistently.
  • Protection against insects: Fewer insects get into the room thanks to the sealed window opening.
  • Greater safety: pets such as cats and small children cannot get through the open window so easily.


Yes, the window can usually be closed even with the flexible window seal still in place. You don’t need to remove the window seal completely every time.

Before closing the window, simply disconnect the external connection:

  • For monoblock units: Remove the exhaust air hose from the window opening.
  • For split-type units: Remove the refrigerant pipes or hoses leading to the outdoor unit from the window opening.

You can then close the window. The window seal remains in place and can be quickly reused the next time you use the air conditioner.

Yes, every genuine air conditioner produces condensation when cooling. The amount of condensation produced depends mainly on the humidity in the room. The more humid the warm air in the room is, the more water can be removed from the air during the cooling process.

The reason for this is simple from a physical point of view: warm air can hold more moisture than cold air. When warm, humid indoor air is cooled by an air conditioner, it can no longer retain all of that moisture. The excess moisture condenses and becomes visible as water.
What happens to the condensation depends on the type of appliance.
In a monoblock air conditioning unit, the condensation produced is first collected in an internal tank. This tank should be checked regularly and emptied as required, for example into a container or directly into a suitable drain. If the tank is not emptied, the unit can evaporate the water internally and discharge it outside along with the warm exhaust air. However, this evaporation process can impair the cooling performance.
With a Cool Air split system from climaexpert or clima2rent, the condensate is drained to the outside via the refrigerant pipes. This ensures that the cooling capacity remains constant, as the condensate does not need to be collected in the indoor unit or evaporated further.

Our recommendations regarding the appropriate appliance size are based on:

  • moderate heat loads in the room,
  • low to normal relative humidity,
  • a standard room height and use,
  • a few additional heat sources.


For larger or more complex rooms, the actual cooling requirement may be higher. If you are unsure which unit is suitable for the size of your room, we would be happy to advise you directly at info@climaexpert.ch.