Attic dehumidification

Damp problems in the attic

According to an investigation carried out by the Swedish National Board of Housing, about 300,000 buildings in Sweden suffer from mould, mildew odours or high moisture levels that can be directly traced to problems in the attic.

  • Cold attic spaces are at the greatest risk

    84% of these attics are cold attics with natural ventilation.
    There are many things that can cause problems with moisture and mould in the attic:

    • Warm moist air from the indoor environment enters the cold attic through unsealed areas and condenses.
    • Additional attic insulation means that the attic gets colder, which means that moisture condenses more easily.
    • Changing a heat source also means changes to the air pressure throughout the house. Switching to ground source/district heating means that a chimney that was previously warm is now cold, and there is no longer any “chimney effect”.
    • Built-in construction moisture can also cause moisture and mould in the attic.
    • The ventilation requirement varies from attic to attic and during the course of the year. Ventilating an attic too much can also cause problems. If the outdoor air is cold, the air in the attic is cooled and can cause condensation against the cold outer roof. Or, when the temperature of the outer roof falls, for example after a warm day, the cooling and the increased relative humidity can lead to condensation on the inside of the roof.

  • Measures that solve the problem of damp in the attic

    • Seal the attic joists and ventilate the living area, not least the wet areas, to prevent the moisture in the air flowing into the attic area.
    • Install permanent equipment for controlled ventilation in the attic space. This creates a suitable environment for all building materials that prevents mould, rot and other microbial damage.

  • Corroventa's solution:

    Demand controlled ventilation withVentoVindTM

    Corroventa’s VentoVindTM is a system which provides optimised ventilation and thereby minimises moisture-related problems such as mould and rot.
    VentovindTM is a system for demand controlled ventilation, which guarantees that the ventilation only takes place when it benefits the attic space. The supply air system ensures ventilation at the right times, while establishing an impression of the attic that breaks up the travel of moisture up from the accommodation.
    • VentoVindTM ensures ventilation of the attic at the right time. The system means that amount of ventilation is precisely enough for the attic requirement, while saving energy.
    • VentoVindTM creates a controlled climate with optimised ventilation without the supply of energy consuming heating.


    1. 9 out of 10 small houses in Sweden have cold attics.
    2. According to Anticimex, over 50% of the cold attics in Sweden are at risk for, or already have, moisture related problems. A study from Chalmers University of Technology found that as much as 72% of all small houses with cold attics in Västra Götaland County had high levels of humidity and mould.
    3. In recent years Chalmers University of Technology and the KTH, the Royal Institute of Technology in Stockholm, have conducted several studies that have shown that excessive moisture and mould in attics is a major and growing problem.
    4. In a detailed study of the Swedish real estate, the Swedish National Board of Housing (Boverket, 2009) notes that the occurrence of mould in cold attics and crawl spaces is increasing. These types of attics are known to have many existing and potential future moisture related problems.
    5. Attic damage is rarely covered by standard house insurance, so it is recommended that the attic is inspected once a year so that problems are detected and rectified as early on as possible, decreasing the overall cost.