Why dehumidification
is necessary

The need for efficient dehumidification is not just restricted to neither water damage, construction work, production processes, swimming pools and waterworks and other obviously damp areas. Buildings, valuables and people in all sorts of climates will often benefit from dehumidification in less obvious everyday situations.

Why do we need dehumidification?

The outdoor air is never completely dry anywhere in the world, and indoors multiple sources add to the relative humidity of the indoor air: transpiration from people; steam from cooking and bathing; humidity emanating from production processes or the storage of damp goods; even building materials and furniture slowly drying out add to the overall humidity of a room.  Due to ever rising energy prices, buildings are much better insulated than before. The insulation might keep out the cold, but it also reduces the air change and traps humidity. A sure sign is dew on on windows, which can easily turn into moisture causing damage to the woodwork.

The main reasons and signs showing that dehumidification is needed:            

  • mould and fungus attacks
  • conditions favourable to microorganisms
  • metal surfaces becoming unpaintable
  • electronic equipment malfunctioning
  • corrosion attacks
  • moisture damages on goods, building parts, furniture, etc.
  • discomfort due to humid indoor climate

In all these instances you need to lower the relative humidity of the air. This can be achieved by different methods. On a hot dry summer's day in Denmark with a room temperature of 20°C and 60% RH (relative humidity), the content of water in the air is approximately 8.5 g water/kg air. In a 80 m3 room this amounts to close to 1 litre water. If the temperature at night drops to 0°C more than 50% of the water content in the air will condense as dew. That is 5 g water/kg air or close to half a litre of condensed water in an 80 m3 room. This could cause all sorts of serious problems.

Heating and ventilation

Warm air holds more moisture than cold air, and for centuries the traditional method for reducing humidity was based on this fact. In the traditional method fresh air is taken into the room and heated up to ensure that it holds more water. Then the air is ventilated out of the room to reduce the humidity. This process is continued until the desired conditions are achieved. During the last few decades this method of heating and ventilating has become more and more obsolete. It is an obviously very energy consuming and uneconomic solution as the heat is - often literally - thrown out of the windows. Furthermore the air taken into the room contains its own relative humidity prolonging the process depending on the time of year, the outside temperature and weather conditions. This is why high energy prices have made dehumidification the preferred economic solution all over the world.


The basic principle of dehumidification assumes that the room is closed. No or at least very little outside air should be allowed to enter the room. The air is continuously circulated through the dehumidifier and gradually the humidity is condensed into a water container with no resulting heat loss to the outside. Quite the opposite to the traditional method of heating and ventilation. Besides the obvious advantages of lower energy consumption, the dehumidification process is much easier to control as long as the room stays closed.

Advantages of condense drying

  • reduced energy consumption (approx. 80% reduction compared to traditional heating and ventilation)
  • less risk of surface drying cavitations and critical point drying because the temperature is lower
  • no energy loss. The electrical energy led to the compressor and fan motor is converted into heat
  • controllable process as the room is closed 


You can download the complete Selection Guide for Mobile Dehumidifiers here: Dantherm Selection Guide

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