Condensation forming on windows

Causes

High levels of moisture within the rooms due to a combination of poor ventilation and not enough heating, poor insulation 

Subfloor dampness getting into the rooms through gaps in the flooring and through service holes cut in framing

No rangehood venting kitchen to steam to the outside, no bathroom exhaust fan venting bathroom steam to the outside; clothes dryers not vented to the outside

Use of flueless gas heating

Common

Listed under: Interior, windows, moisture, condensation

Cause

High levels of moisture within the rooms due to a combination of poor ventilation and not enough heating, poor insulation 

Repair

  • if there are high internal moisture levels:

    • avoid using unflued gas heaters and avoid drying laundry inside – these add a lot of moisture to the air

    • opening windows for at least 10 minutes every day can make a difference to indoor air quality

    • increase the amount of ventilation provided. In particular, add a rangehood over the kitchen stove and an exhaust vent near the shower in the bathroom, both vented to remove steam to outside the house. An alternative to reduce bathroom steam is to fit a proprietary plastic dome over the shower to keep the steam inside

  • where possible, improve the heating in the rooms. See the Level website details on heating, including comparisons of running costs of different types of heaters

  • where possible, add insulation in the ceiling space and under the floors. See the Level website for more details. There may be funding available to help with the cost

Back to top

Cause

Subfloor dampness getting into the rooms through gaps in the flooring and through service holes cut in framing

Repair

  • where air is carrying subfloor moisture up through floorboards, install underfloor insulation, with sheet lining underneath it if necessary to stop airflow. Rental properties with suspended timber ground floors must have underfloor insulation installed by 1 July 2019

  • where possible, locate and seal holes in the framing and seal gaps around service pipe penetrations

  • if there are high sub-floor moisture levels:

    • identify the cause of the subfloor moisture and address it. If it is caused by a leaking pipe, make a repair, or call a licensed or certifying plumber to repair it. Work on waste pipes and drains must by law be carried out by a licensed or certifying plumber

    • if surface water is flowing under the house, lower the ground levels around the building and slope the ground away from the house. Install channels or sub-surface drains and discharge into a stormwater drain or soak pit 

    • lay polythene sheeting at least 0.25 mm thick to cover the ground under the house. Ensure that the ground is shaped so no water accumulates on the polythene. Polythene sheets should be lapped a minimum of 150 mm, preferably taped, and butted up to foundation walls and piles. Weigh down the sheets with bricks or concrete to avoid them being displaced by air movement

    • improve subfloor ventilation.

Back to top

Cause

No rangehood venting kitchen to steam to the outside, no bathroom exhaust fan venting bathroom steam to the outside; clothes dryers not vented to the outside

Repair

  • increase the amount of ventilation provided. In particular, add a rangehood over the kitchen stove and an exhaust vent near the shower in the bathroom, both vented to remove steam to outside the house

  • an alternative to reduce bathroom steam is to fit a proprietary plastic dome over the shower to keep the steam inside

  • where possible vent a clothes dryer to the outside, or at least use near an open window. Unvented clothes dryers can release an average of 5 litres of moisture per load into the indoor air

  • opening windows for at least 10 minutes every day can make a difference to indoor air quality.

Back to top

Cause

Use of flueless gas heating

Repair

  • replace flueless gas heating with another heating option – this type of heating can release an average of one litre of moisture into the air for each hour it is operating. See the Level website details on heating, including comparisons of running costs of different types of heaters

Back to top