The Condensation Conundrum

24 August 2018
Posted by: Evolution
Time to read: 3 mins.

The Condensation Conundrum

How to Cope with Moisture in the Home

Condensation forms when the water vapor in the air is changed into liquid water. In other words, the water in the air, which is in gaseous form, cools and turns the gas into liquid.  An example of this process is when water from your hot shower cools and condenses as it meets the surface of your cold mirror, misting it up. 

Warm air can carry more moisture, so a warm house is less likely to have condensation but will still require ventilation to keep moisture at an optimal level.  If you don’t ventilate your home, moisture will collect and wherever it meets a cooler surface, will condensate.  If that condensation is left, mould will grow, particularly at warmer temperatures.

Every home requires ventilation, whether passive or active, to keep moisture levels at a reasonable level.  An active system is provided mechanically, including exhaust fans, rangehoods and automated, balanced ventilation (i.e. Mechanical Heat Recovery Ventilation), which is the ideal way to keep fresh air in the house while expelling stale, moist air. 

JFK 1826 51 Medium2

Mechanical Heat Recovery Ventilation installed in Evolution home in 2012

Without an automated system, the responsibility falls on the occupant to ventilate the home.

Here are eight tips on managing the moisture in your home:

1.  Make a point of ventilating the home once a day; Create cross ventilation by opening windows or doors on opposite ends of the house or by turning on an exhaust fan to pull air through.  Create this cross ventilation for a minimum of 10-15 minutes. This airs the house out without letting surfaces get cold, which will take extra energy and time to warm up again.

 Cross Ventilation e1477632264350

2. Do not dry clothes indoors! Keep them in the garage or under a covered area outside if not using a dryer. If a dryer is in use in the home, make sure it is either a condensing dryer or that it exhausts to the outside.

3.  Turn on exhaust fans in bathrooms a few minutes before taking a shower or bath.  To promote airtightness, we specify exhaust fans with dampers, preventing outside air from leaking in when the fans are not in use.  It takes a few minutes of operation before they open up fully and air is being sucked to the outside.

4.  When cooking, use the rangehood fan.  If steam or smoke is rising, it should be pulled right into the rangehood, so select the setting accordingly.  Don’t forget to clean the filter as grease can quickly build up and clog the intake, compromising the operation of the rangehood fan.

5.  Check that exhaust fans are working properly every six months, and replace or clean fans and filters as necessary.  You can conduct a quick check by turning on the fan for a few minutes and placing a piece of paper or playing card on it.  The suction should be sufficient to hold the paper or card in place.


extractor fan3

Easy DIY extractor fan test


6.  Run a dehumidifier at night, particularly in a bedroom with a closed door.

7.  Keep the home evenly warm; don’t let the temperature fluctuate as this will bring the dew point inside the thermal envelope.  Using a thermostat is the most effective and easiest way to ensure the home’s temperature is constant within a few degrees.

8.  Aluminium joinery is particularly prone to produce condensation because it is highly conductive of temperature.  Minimal condensation may still form at the base of a window, even when it has a plasticized thermal break separating the inner aluminium from the outer.  If this happens, take a clean, soft cloth and wipe all moisture away.  Do not leave it as this moisture will be prone to growing mould, particularly in a warm environment.

It may seem counter-productive to expel warm air from your home and incur heat loss, but it is easier, faster and requires less energy to heat fresh, dry air.  In the end, it shouldn’t cost more in power to keep the home well ventilated. 

The ideal scenario is to incorporate an MHRV, efficient heating system and airtightness into the design-and-build of a new home. 

If this is too late, one option is to retrofit individual units by Lunos.   The Lunos eGO is an all-in-one room ventilation system with a built-in regenerative heat recovery core, ideal for bathrooms and single room spaces.


Lunos e-go, heat exchange ventilation unit

For related articles, read "An Airtight Explanation" to learn more about the benefits of an airtight envelope.

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