Crawl space dehumidification

  • Damp in crawl spaces

    Moisture and water damage are one of the most common problems that affect a house holder. Damp, in itself, is completely harmless, but damp together in combination with organic materials, such as for example in a crawl space, often causes problems in the form of mould, fungus and odours. These problems, in return, increases the risk of allergies and asthma in children.
    There are house structures with crawl spaces that are unventilated, indoor air ventilated or outdoor air ventilated. The latter type of crawl space, i.e. the outdoor air ventilated type, is usually extremely sensitive to moisture.

  • This is how damp in crawl spaces occurs

    If the moisture level in a crawl space becomes so great that it turns into a problem, it can depend on one or several causes, such as:
    • A: When hot outdoor air enters the cold crawl space via vents or cracks, it cools down. At this point the air humidity increases. In extreme cases condensation and water drops are created that hang from the ceiling above.
    • B: Addition of damp air through evaporation from the ground surface of the crawl space.
    • C: Moisture enters from the surrounding area through the foundation wall and leakage in the foundation construction.
    • D: Water that penetrates the crawl space through the foundation walls all around.

  • How the problem is solved by dehumidifying the crawlspace

    • Route the water away from down pipes and similar that exit next to the foundation wall.
    • Cover the ground in the crawl space with a plastic sheet to prevent moisture evaporation.
    • Block and seal all vents and cracks in the crawl space so that no outside air enters.
    • Permanently install a crawl space dryer that maintains humidity at such a low level that mould, fungus etc. is prevented.

  • Adsorption dehumidifiers are the right technology for crawl space dehumidification

    The temperature in the crawl space varies between 4 and 15 °C through the year and the relative humidity should be around 65-70 %. The diagram shows which type of dehumidifier works best in different climates. Since the climate in a crawlspace is within the red area during all seasons, an adsorption dehumidifier is the best technology for crawl space dehumidification. Condensing dryers are superb for warmer temperatures but work badly or not at all for crawl space climates.

    See our adsorption dehumidifiers for crawl spaces>>


  • Corroventa's solution:

    Adsorption dehumidifier CTR 300TT2 and control equipment HomeVision®

    Adsorption dehumidifier CTR 300TT2 has been part of our range for 15 years and is one of our faithful servants. It is specially designed for use in crawl spaces where the requirements are for robustness, operational safety and long service life. Effective against moisture, odours and radon.
    The HomeVision® control system is used to achieve controlled dehumidification in crawl spaces. Control, regulation and monitoring of the crawl space installation occurs via a hygrostat connected to the dehumidifier in the space and a wireless control panel in the living area.

  • The dehumidification process

    When outdoor air, particularly during the warm times of year, enters the crawl space (D) under the house it is cooled by the cool environment and the relative moisture increases and, therewith, the risk of mould attack and odours. By drying the air, so that the relative humidity remains below 60-65 %, mould can be prevented.

    The air in the crawl space is sucked into the dehumidifier (A). The dry air (B) must be distributed in such a way that the crawl space remains dry. At the same time as the dehumidifier dries all the air it removes all moisture (C) from the crawl space to the surroundings. The dehumidifier is designed so that it does not just dry the air, but that the air volume (C) that leaves the crawl space together with all moisture can be varied (without the dehumidifier capacity or operating cost being affected). In this way, the negative pressure in the crawl space (D) is controlled so that any odours (E) are slowly sucked down into the crawl space and, via the dehumidifier, out to the surrounding area.