2018-02-26: Breaking the Mould: Should landlords be doing more?: The first phase of the study has now been completed, and showed clear links between the severity of mould and incidence of respiratory conditions. Some species of mould can be highly toxic, and disturbing while cleaning can sometimes be hazardous. The study also revealed that mould is most likely to occur in homes with higher occupant density, and in homes that are less well insulated. ... and Residents do not always link the importance of ventilation with their experience of condensation and mould. They are often much more concerned with keeping the heat in, than with a regular ventilation regime. Clear advice from landlords on good ventilation practice could help residents manage condensation and mould issues. ...
English Housing Survey Energy Report, 2014: 4.1. Condensation occurs when moisture that is held in the air (water vapour) comes into contact with cold surfaces and condenses into water droplets. Over time, the area can become damp. Mould can grow when relative humidity is above 80%. ...