Find the answer to: Why is a desiccant dehumidifier the best choice for drying out after water damage?
Target condition of 30–50%RH:
In most cases (in Northern Europe), the typical goal for a dehumidifier is to create an environment with 30-50% relative humidity (RH) in the heated room to be restored at 20°C. Read about the reason here: Optimal Humidity Range for Water Damage Restoration: 30-50%
Dehumidification Principles:
After running for a short while, the dehumidifier should achieve the condition mentioned above. That means the incoming air to the dehumidifier will be in this relative humidity range and temperature range. Therefore, the dehumidifier's performance must be specified for the target condition.
A condensation dehumidifier works by cooling the air down to below the air's dew point, whereby the moisture in the air will start to condense as water droplets.
Video explaining the dew point and how condensation occurs
Suppose you have 20°C in the room and want a humidity of 40% to dry out the water damage, which corresponds to a dew point of 6°C. In other words, the condensation dehumidifier must cool the air from 20°C to 6°C before the air starts to condense water. This initial cooldown is a loss and a waste of energy. Subsequently, the air must be further cooled to release water. This is complicated, as we are close to the freezing point and thus risk the whole thing freezing to ice, meaning the troubles with condensation dehumidifier increase with lower temperatures.
Usually, a condensation dehumidifier's capacity is specified at 30°C and 80%RH, and it often has good efficiency in this warm and humid condition. But you cannot use this directly for dimensioning for water damage as the working conditions are entirely different. A condensing dehumidifier will have approximately 80-85% lower capacity at 20°C and 40%RH compared to 30°C and 80%RH (often, it would not even work at 20°C and 40%RH).
In short, an adsorption dehumidifier divides the incoming air stream into a dry and wet one. It uses silica gel for the process. Silica gel can be understood as a water molecule magnet that absorbs water and re-releases it with dry (warm) air.
Video explaining how an adsorption dehumidifier works
An advantage of this principle is that it works at very low temperatures. Cotes has dehumidifiers standing in freezing houses at -30°C without problems.
The capacity of a desiccant dehumidifier is usually given at 20°C and 60%RH. The capacity of a CL26 will be 20% less at 20°C and 40%RH, meaning you will still have a lot of capacity at the target condition.
Comparing capacities at target conditions:
For water damage in a room of 100m3, you would need a dehumidification capacity of 0,6 to 0,9l/h* at room condition (20°C and 40%RH), adjusted according to the extent of water damage*.
Usually, a desiccant dehumidifier is specified at 20°C and 60%RH. In this instance, you should then choose a capacity of 0,7 to 1,1 l/h to make sure you have the needed capacity at the target condition (20°C and 40%RH). Whereas, a condensation dehumidifier is specified at 30°C and 80%RH. Here, you should then choose a capacity of 2,8 to 3,7 l/h to make sure you have the needed capacity at the target condition (20°C and 40%RH).
But please note that some condensation dehumidifiers struggle to work at low relative humidity and/or low temperatures. We have tested refrigerant dehumidifiers, making zero at 20°C and 40%RH. Generally, if the datasheet does not provide the capacity in the targeted condition, you should inquire about it.
Energy efficiency:
The dehumidifiers consume more or less the same amount of energy, regardless of their placement and dehumidification level. This highlights that a condensing dehumidifier placed in the target condition (with reduced capacity by 80-85%) will consequently exhibit poor energy efficiency.
Conclusion:
While a condensation dehumidifier may appear to perform well, it is crucial to assess its performance under the target condition. It could be 80-85% less effective than specified or may not work at all.
On the other hand, a desiccant dehumidifier will work in all conditions. The Cotes Window Kit makes it as easy to install. See how to install fast here: How to setup the Cotes Window Kit with a Cotes dehumidifier in 3 easy steps
Note:
* Extent of water damage is here given by a class 2 (low number) and class 3 (high number):
Class 2 Water Damage is characterised by a significant amount of water absorption and evaporation load. It involves water intrusion where wet porous materials (like carpet, gypsum board, fibre-fill insulation, concrete masonry unit, and textiles) represent approximately 5% to 40% of the space's combined floor, wall, and ceiling surface area. The materials described as low evaporation materials or assemblies have absorbed minimal moisture.
Class 3 Water Damage is marked by the greatest amount of water absorption and evaporation load. This type of damage occurs when water intrusion affects more than 40% of the space's combined floor, wall, and ceiling surface area, involving wet porous materials similar to those in Class 2. Like Class 2, the materials considered low evaporation materials or assemblies have also absorbed minimal moisture.