Desiccant Dehumidifiers in Floods & Water Damage
A major set back in the restoration process is the time taken to dry out buildings prior to starting
remedial building work. There are potentially hundreds of litres of water that remain hidden within the
As a result, buildings remain unfit for use or occupation
for many months during which time high internal humidity
levels can cause secondary damage and increase the
risk of dangerous mould growths.
Whilst the drying rate of a material will vary according to
its porosity and density, it is also determined by the
ability of moisture to evaporate into the surrounding air.
Drying rates are greatly improved by lowering relative
humidity, adding heat and increasing air movement.
Ideal drying conditions of 35 to 55 %RH can only be
maintained if the dehumidifier capacity is greater than the
rate at which moisture is being evaporated. If the internal relative humidity rises uncontrollably (e.g.
condensation on external walls), it is a clear indication that the dehumidifier capacity is too small.
Dehumidification of flood damaged buildings
The primary benefit of a refrigeration type dehumidifier is that it performs well when used in a warm
humid environment. Moisture extraction rates will deteriorate rapidly as both temperature and humidity is
reduced. It is generally accepted that refrigeration dehumidifiers should not be used below 10°C
A desiccant dehumidifier operates on a totally different principle to a refrigeration type. The main benefit
is that it performs exceptionally well when used in cooler climates, or when lower dew points are
required. As there is no water produced during the drying process, these units work effectively at sub-
Air leaving a desiccant dehumidifier is warm, very dry and at high velocity,
thereby providing the three essential ingredients necessary for fast and
effective drying. The dry air can be easily ducted to where drying is needed most, whether it is under a floor,
into a wall cavity or simply distributed to serve multiple areas.
Whilst the purchase of a desiccant dehumidifier is probably not within the financial budgets of most home
owners, some restoration companies now provide small desiccant units for hire. High capacity desiccant
dehumidifiers should be used for drying larger buildings such as schools, warehouses, municipal buildings, etc