How evaporative cooling works

Prior to being cooled by evaporative evaporation, the outdoor air is initially hot and relatively dry, and so the air has a high proportion of (red shown) so-called "sensible heat".

The primary process

As the airflow passes over the water, water evaporates into the air. The heat energy necessary for the evaporation is withdrawn from the air. The sensible air temperature decreases continuously. The evaporated humidity absorbed by the air is also referred to as "latent heat". Since the total energy of the air-water system remains the same with this exchange of sensible heat to latent heat, this type of evaporation is called "adiabatic" (this is taken from the Greek term for a change of state without the direct addition or removal of heat).

The secondary process

As the evaporative cooler cools down the air, the secondary phase is to remove the latent heat from the building. The temperature in the building falls as a result of the heat dissipation in the desired manner.

In the case of CoolStream, a special material is used to transport the water with many small channels through which flows the warm and relatively dry outdoor air, without having to have contact with droplets from the water distribution system. When passing through this wet medium the warm air is cooled considerably by the removal of sensible heat and this can then be used to cool down the building.

The temperature of the air passing through can be lowered by up to 15°C in Europe and in the Middle East by up to 20°C.

Efficient and cost effective cooling – the hotter the better

In general, the hotter the weather, the more efficient the cooling is. Evaporative cooling is up to seven times more economical than conventional air conditioning systems, and has lower initial costs.

Maintaining excellent year-round conditions


In summer, Coolstream S.T.A.R systems provide direct evaporative cooling. External air is brought into the internal space from roof level over a special cooling medium and supplied to the room.

Spring and Autumn

In spring and autumn there may still be residual cooling demand, for example where there is a high internal heat load. CoolStream T, A and R systems mix outdoor air with warmer high level internal air via a process of destratification, in such a way that supply air is pre-heated.


In the winter months CoolStream R systems can combine the warmer high level internal air with external supply air to achieve the desired temperature. The proportion of outdoor air is reduced to a minimum to necessitate as little heating energy as possible and heat is reclaimed.

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