Understanding condensation and ventilation in roof spaces
Condensation occurs when warm air from the main rooms in a house rises, often reaching the loft space and meeting the much colder part of the roof deck. If a surface is cooler than the dew point temperature – the point when air will be fully saturated with water vapour – condensation will occur as droplets. Condensation is caused by poor ventilation in the roof structure, as well as air leakage into the attic caused by poor insulation between the room ceilings and the floor of the attic. Over time condensation can cause issues within a loft space, whether that is causing damp and mould on exposed insulation or soaking the wood of the roof structure. In extreme cases this can leak through the ceilings to the rooms below.