‘Surface condensation occurs where the temperature of a material falls below the dew point. Where air reaches a relative humidity of 100%, it will allow water vapour to change from gas to a liquid and free water will be deposited as condensation.’

Property Care Association Code of Practice: The Investigation and Control of Dampness in Buildings

Condensation is a common occurrence in properties and in excessive amounts, can be come a nuisance. Condensation is caused by moisture released by occupants either directly (breathing), or indirectly (drying clothes). When the moisture laden air encounters a cold surface, it changes from a vapour to a liquid, forming the familiar streaks of moisture usually on windows.

Often associated with this is black spot mould, usually the Penicillium or Cladosporium variety. This provides an unsightly surface.

Causes of mould are generally associated with:

  • cold bridging (this is where a dense element of the construction creates a cold surface i.e. concrete lintel);
  • poor ventilation of the property;
  • increased occupancy;
  • poorly insulated properties and inadequate heating

Condensation is more prevalent in the cooler months of the year, also known as ‘condensation season’.  This is attributed to a lower surface temperature and decreased ventilation within a property i.e. windows not being opened.

The health risks associated with mould growth in buildings are generally confined to agricultural exposure and include:

  • Irritation of eyes, nose and throat
  • Dermatitis
  • Exacerbation of Asthma
  • Allergy
  • Aspergillosis

Other health effects have been reported but have not been proven. If there is concern over an occupant’s health, a health professional such as your local GP should be consulted immediately.

However, it is worth taking into consideration that there has been some in-depth studies from peer reviewed papers, which found the following:

Health Alert published by University Health Publishing and John Hopkins Medicine

‘’Just because a particular mould can produce toxins doesn’t mean it will. Even if the mould is producing toxins, a person must breathe in a sufficient dose to be affected. It is highly unlikely that you could inhale enough mould in your home or office to receive a toxic dose’’

American College of Occupational and Environmental Medicine council on scientific Affaris. Evidence-Based Statement. Adverse Human Health Effects Associated with Molds in the indoor Environment. JOEM 2003: 470-478

‘’Current scientific evidence does not support the proposition that human health has been adversely affected by inhaled mycotoxins in the home, school or office environment’’

It should be known that there have been some associated health effects associated with a damp environment but not exclusively to the presence of mould. Therefore, it is important that emphasis is placed on correcting the source of damp. This is confirmed by the World Health Organisation and the Institute of Medicine. (

Landlords should familiarize themselves with the Environmental Protection Act 1990, Chapter 43, Section 82. This highlights that, ‘’It is a landlord’s legal responsibility to deal with dampness problems as well as it being a duty of care.  The main problem is condensation, which is always nearly seen as mould growth. Under the law, this can be deemed as a statutory nuisance. An action can be brought under the Act, which is of a criminal nature and can attract significant fines’’.

As highlighted above, if there is concern over an occupant’s health, a health professional such as your local GP should be consulted immediately.

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