Mould can grow almost everywhere and on any substance providing moisture is present. Thus, the best method of prevention is to reduce the amount of moisture.
Keep the relative humidity between 30% and 50%.

To accomplish this goal, prevention measures include:


  • Install ventilator in roof with ceiling registers (vents) located in rooms with poor natural ventilation which will assist in combating condensation.
  • Insulate cold surfaces to prevent condensation on piping, exterior walls, roofs and floors where possible.
  • To assist prevention of condensation, keep open a number of windows at night. For safety reasons security screens should be installed.
  • Control humidity with air conditioners and/or dehumidifiers when outside air is warm and humid.*

* It is important to remember that when using air conditioners and dehumidifiers to empty any water collectors regularly so this water does not contribute to the moisture problem! If you use humidifiers, ensure that the filter is cleaned regularly.

Bathroom / laundry

  • Always vent showers/bathrooms with the correct rated extraction fan output (refer section below called “How to size an exhaust fan for a room”).
  • In the laundry, the clothes dryer should be ducted outside. One load of cloths will add 2-3 litres of moisture into the air. If you live in a unit/apartment where your laundry is located in a cupboard, check with the resident manager if the doors of the cupboard should be closed when in use where vents exist inside.
  • Use a condenser style clothes dryer if it is not vented outside.
  • Don’t leave wet clothes or dry naturally (e.g. cloths rack) inside.
  • If you live in a cold environment use heated towel rails so they dry between uses.
  • If your bathroom does not have good natural ventilation, leave your shower door ajar and leave on the vent so this area can dry. Also clean the shower/bath regularly preventing mould growth.


  • Use exhaust fan in kitchen when cooking (stove and oven) and using the dishwasher or washing dishes.
  • Watch out for mould around the refrigerator / freezer seals.
  • Ensure any rotten food is disposed of ASAP.

Living area

  • Keep the heating, ventilation and air conditioning (HVAC) systems in good repair.
  • Clean up any spills immediately and if you incur water damage seek professional restoration within 24-48 hours of the occurrence.
  • For floors and carpets, remove spots or stains immediately.
  • Vacuum carpet regularly and keep it in a healthy condition with professional carpet cleaning every 12 to 18 months for homes and 6-12 for commercial premises.
  • Do not install carpet around fountains, sinks, bathtubs/showers or directly on top of concrete floors that are prone to leaks or frequent condensation.
  • Always air shoes outside before bringing them inside.
  • If you have indoor plants, ensure to water them outside and ensure they are completely drained before bringing them back inside.


  • If your home is prone to dampness underneath (in the crawl space) install sub-flooring ventilation.
  • Ensure water flows away from the building/home when it rains and avoid gardens next to the building.
  • Regularly check and keep your gutters clean so downpipes do not get blocked and overflow.

How to size an exhaust fan for a room

  • Measure the size of your room  - Volume(cubic meters) = length x width x height.
  • Multiple by the number of times the room air is vented per hour. It is recommended a minimum of 25 at least – Required volume(cubic meters) = Volume x 25
  • Fans are rated (air flow rate) in one of two ways:
    Cubic meters per minute = Required volume ÷ 60
    Litres per minute = (Required volume x 100) ÷ 60

Example – Our room measures 3.5 meters x 4 meters x 2.3 meters high; Volume - 3.5 x 4.0 x 2.3 = 32.2 x 25 = 805 (Required volume). We require an exhaust fan rated at 13.42 cubic meters per minute (Required volume ÷ 60) or 1,342 litres per minute ([Required volume x 100] ÷ 60).