Condensation can be caused both by defects in the building fabric and the occupants use of the building.  As with any defect the correct diagnosis is vital in helping to deal with the problem. 

 

Cold bridging in the structure can result in condensation.  A cold bridge or thermal bridge is a where there is a break in the continuity or a penetration of the insulation. This will often occur at junctions in the structure such as at the junction of floor and external walls or at window and door heads.   The break in the insulation allows for a significantly higher heat transfer and will result in the area being significantly colder than surrounding wall.  Therefore if there is sufficient moisture within the air water droplets will form when the air comes into contact with the colder surface.  Condensation as a result of cold bridging can be identified by damp patches and mould growth with defined edges.  Care should be taken when identifying this type of condensation as the signs can be very similar to that of rising and penetrating damp.  Remedial works for this type of condensation will involve opening up the structure and may involve reconstruction of defective details to ensure a continuation of the insulation. 

 

Condensation as a result of occupants’ behaviour will generally result in damp patches and mould growth without definite edges that are associated damp defects.  Impermeable surfaces such as gloss paint or paper will often be covered in a fine film of water droplets.  Water droplets will also often form on window and door panes, with water accumulating on the window boards.  Dampness and mould growth will generally start in colder areas with little airflow such as corners or behind furniture or units.  Rooms with high moisture levels are more susceptible such as kitchens and bathrooms. The control of condensation involves maintaining surface temperatures above the dew point (the humidity related temperature at which water vapour turns into moisture), and the provision of adequate heating and proper ventilation.  Unfortunately, the modern emphasis on draught proofing reduces ventilation in dwellings, increasing the risk of condensation.  Extractor fans with over run capacity should be fitted to kitchens and bathrooms to help improve ventilation.