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What causes condensation and how to reduce it

20 June 2018
What causes condensation and how to reduce it

It is a common misconception that windows produce condensation. This is not true, windows cannot produce condensation. Condensation is formed when moisture in the air comes into contact with a cooler surface such as a window.

Main Causes of Condensation

1. You and your family's activity within your home

This is the main cause of condensation within a home, excessive moisture is generated without sufficient ventilation. Everyday household activities can produce litres of moisture within the home.

Household Activity Average moisture added to the indoor air
Cooking 3.0 litres day
Clothes washing 500 ml per day
Showers and baths 1.5 litres per day per person
Dishes 1.0 litre per day
Clothes drying (unvented) 5.0 litres per load
Gas heater (unflued) 1.0 litre per hour
Breathing 20ml per hour per person
Pot plants As much as you give them

2. A new construction of a home during the rainy season

When a house is closed in during construction in a particularly wet season, then the amount of moisture that is released while the house dries out and trapped within the home of the first year is significant (read article here). Up to 1,000 litres can be released from the slab alone, let alone framing, carpet etc. This applies to most new houses and the solution for this is that they live in the house for 12-months and contact their builder after that if the problem still exists. It is a hard one to sell to the proud owner of a new home, but in the far majority of the time the problem simply goes away once the moisture within all the building products dries out.

3. Location

The only other problem has been when the site has particularly unique location challenges, e.g. amongst trees down in a gully.

How to reduce condensation

1. Ventilation

Ventilation can help reduce moisture and condensation, keeping your home drier, healthier and more comfortable. Keep windows open during the day to let moisture escape. When cooking, drying laundry, or showering, make sure you let the water vapour escape outside. You can do this by opening windows or vents or turning on a ventilation fan.

2. Double Glazed Windows

Using double glazing can help keep the surface of the inside glass warmer and so reduces the likelihood of condensation forming on the windows. Though, you must remember that moisture is still present within the home.

3. Thermally Efficient Window Frames

Like double glazing, thermally efficient window frames can help prevent the transfer of heat energy through window frames and therefore help reduce the incidence of condensation on windows. Thermally efficient window frames should only be used with double glazing.

4. Dehumidifiers

Dehumidifiers are useful as their sole purpose is to reduce moisture in the air. A dehumidifier draws in the moisture laden air from around the room, extracts the water and deposits it into an inbuilt container. You can easily dispose of this water by removing and emptying the container.

5. Ventilation System

There are several types of domestic ventilation system available. They work by replacing the moisture-laden air in your home with air that may be drier – potentially reducing condensation and improving air quality as a result. Some systems have built in electric heaters that can also warm your home.

You can read more information about condensation on the independent industry website: www.wanz.org.nz