Damp caused by the condensation of water vapour occurs when the vapour passing through a wall reaches, at some point along its path, the saturation temperature or dew point. The typical symptom of this type of damp is a dark brown stain that turns deep black as a large colony of mould forms, with a characteristic smell. The cause lies in insufficient insulation of the building envelope, especially at certain points (thermal bridges).
Thermal bridges are weak points in thermal terms, and can be defined as the set of points on an interior wall surface whose surface temperature remains lower than that of the rest of the surface. If the temperature is below the estimated dew point of the air in the room, condensation of water vapour will occur.
To avoid these thermal bridges, the design of the works must provide for continuous thermal insulation on either the inner or the outer side; otherwise the thermal insulation is interrupted, leaving these points completely unprotected, and the result is the spread of condensation damp.
Likewise, the insulation must be installed correctly, fixed to a wall, so that the element performs properly in thermal terms, and there must be no gaps around the window frames or at junctions with structural elements, in order to prevent damp from appearing.
Condensation damp is particularly troublesome and can significantly affect the habitability of the home, encouraging the growth of fungi and mould, etc…; it makes it impossible to keep rooms healthy and clean, and also affects the healthiness of the home, with possible harmful effects on the occupants’ health (it can cause allergic reactions, lung or respiratory illnesses, headaches…).
That is why it must be repaired at source; simply painting over it is not acceptable, as that would be a superficial fix that does not tackle the real cause of the problem.
NOTE: Condensation damp results in a failure to meet the habitability requirements of section 1, letter c), of article 3 of the LOE, and to claim for it you must do so within two years, provided the damage has appeared within 3 years of the completion of the building.
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