Suction drying and dehumidification of layer floor constructions

  • Suction drying is an effective and simple method for drying layered constructions. Suction drying should always be used as a first stage when drying floors on concrete slabs, where the water has leaked down into the fill or insulation under the floating floor. Corroventa has a number of products that are used for drying layered constructions such as walls, ceilings and floating floors. From flexible system solutions with dehumidifiers and turbines to the patented Combi series that offers the possibility of both pressure and suction drying in the same machine.

    Picture: A turbine that is suction drying a floor construction with water separator and combi filter.

  • Suction drying – an effective and simple drying method

    The suction drying technique is based on a dehumidifier drying the air in the room at the same time as a turbine creates a high negative pressure in the construction. The dry air in the room is sucked down, in and through the construction, via air gaps or drilled holes. The damp air is then sucked out of the construction via a water separator of 3-Step Filter type, before it exits the room through the turbine. A 3-Step Filter water separator is a very efficient way of removing water, dirt and dust using the same unit. It is used to clean the air and protect the turbine.

  • Always use suction drying

    Suction drying is always used as the first step prior to pressure drying; this is done to avoid forcing the free water further out into the construction. When all the excess water in the construction has been sucked out, a decision can be taken to change to pressure drying or to continue with suction drying until the construction is dry. Suction drying takes somewhat longer compared to pressure drying but it is a better technique to use where there is a desire to minimise the risk of fibres or dust particles finding their way into the room air. If the air needs further cleaning, for example when working in occupied residential spaces when the air cannot be evacuated into the surroundings, it can be an advantage to use a HEPA H13 multifilter. A HEPA H13 multifilter cleans the air up to 99.95% and the inbuilt carbon filter removes unpleasant odours.

  • Combi machine for pressure and suction drying

    As with pressure drying, it is often more suitable to use a Combi machine when suction drying. A combi machine comprising dehumidifier and turbine in the same unit, which facilitates and simplifies installation. The extremely low noise level also makes it more suitable for occupied residential spaces.

    Hose systems

    Corroventa’s C16 and C25 hose systems can be used to transport air while suction or pressure drying. The hose system is modular and includes junctions, hoses, pipe bends and T-connections. The system, which includes CAMLOC couplings, provides a simple, quiet and reliable installation.


    In order to ensure that harmful particles do not enter the machine during suction drying, a Corrofilter must be used on the hose system for the wet air entering the turbine. The filter prevents dirt particles from being sucked into the machine, and at the same time, it eliminates the risk of fibres and other damaging particles being expelled into the surroundings along with the moist air. The Corrofilter consists of three units; a coarse filter, cyclonic separator and fine filter, using a HEPA-filter. The filtration efficiency is 99.5% for particles larger than 1um and 99.967% for fibres and mineral wool. Corrofilters are not intended to separate water; instead, a 3-Step Filter should be used for water separation.

    Water Separator with 3-Step Filter System

    When suction drying damage where there is free water, such as insulation in floating constructions, a water separator must be used to separate the water from the moist air stream and to prevent water from being sucked into the turbine section of the machine. We have developed a water separator with a 3-Step Filter System for the efficient separation of water, granulates and fibres during suction drying of layered constructions for use with our range of Combi and turbine systems.

    The air is cleaned in the following steps

    Step 1 – coarse separation
    In the first step, gravel, sand and other large particles are separated from the incoming moist air stream.

    Step 2 – water separation
    Water and liquid droplets are separated from the air stream in a so-called droplet separator. When there is a given amount of water in the reservoir, a level sensor starts a submersible pump that automatically pumps the water to a drain.

    Step 3 – particle and fibre separation
    In the final step, the small particles and fibres are separated in a HEPA-filter, after which the clean moist air can exit into the surroundings through a turbine. The filtration efficiency is so high that 99.5% of all particles greater than 1µm are filtered out.

    Shorten the drying time with heat

    To shorten the drying time, the temperature of the air used for drying can be increased. The warmer the material to be dried is, the more efficient and quicker the drying process will be, as the vapour pressure in the wet material increases. An increase as small at 10°C can halve the drying time* in some cases *Because the drying rate is directly proportional to the difference in vapour pressure, this means that drying at 30°C 20%rh is theoretically twice as fast compared to 20°C 20%rh.

    Important to consider before suction drying

    It is important to bear in mind that the dry, warm air also affects all wooden material in the room where the drying process is being carried out. For this reason, care should be taken to remove or carefully wrap in plastic all furnishings that could possibly be damaged. If possible, plastic enclosure can be used, to limit the area to be dehumidified, and in this way protect surrounding material. A hygrostat can be used to advantage, to control the humidity during the drying process.