Articles

Why is moisture so damaging to a home?

Published 5 Jan 2016 by Paul Goodwin in Moisture testing

Moisture

Internal moisture can be a major problem, particularly in the colder parts of the country. Air inside the building holds water in the form of water vapour. The warmer the air the more vapour it will hold. When the moist air comes in contact with cold surfaces liquid water is formed as condensation.

The major sources of internal moisture are:

  • Flueless gas heaters
  • Showers and baths
  • Drying clothes inside
  • Cooking
  • Breathing and perspiration by occupants
  • High levels of Subfloor moisture
  • Uninsulated ceiling space.

The obvious sign of high levels of internal moisture is surface condensation. Condensation is more obvious on hard, impervious surfaces such as glass or gloss painted ceilings, but it will occur on any surface which is colder than the (dew point) air temperature. It is more likely to occur in rooms which are occupied but not heated, because the low room temperatures mean the air can hold less moisture and the extra moisture will readily condense on the cold walls.

Condensation, if left unchecked:

  • Leaves water stains
  • Promotes mildew growth
  • Can cause swelling and rotting in wood and wood based products
  • Can rot carpet.

So how can I minimise moisture levels?

Reducing high internal levels of moisture often requires a change in the way the building is used. A modern home; that is those built after the 1970’s, are more airtight than older ones and they require slightly higher levels of ventilation to remove moisture-laden air.

The effects of internal moisture can be minimized by:

  • Keeping the room and its internal surfaces warm. The indoor temperature should be kept at least 5 - 7°C higher than the outside temperature
  • Continuously using low levels of heat in all living and bed rooms) to minimize temperature fluctuations and to keep surfaces warm, rather than using a lot of heat for a short period
  • Constantly ventilating the space to remove moisture-laden air to the outside ( opening windows, installing permanent ventilators or security stays, dehumidifiers or ventilation systems
  • Insulating or increasing the level of insulation, particularly in the ceiling
  • Installing extractor fans, vented to the outside, in bathrooms and kitchens.