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Summer moisture in the home

3 February 2016
Summer moisture in the home Summer moisture in the home Blog

The El Niño weather conditions during past weeks have created (wet) sticky and humid temperatures over most of the country. It's interesting to reflect on the effect this has inside our homes and how it relates to home ventilation systems.

Our homes are surrounded by air (outside) which is always eventually the source of air brought into a house no matter how we get it there – open windows, suck it in through vents in the wall, suck it in through the roof space via vents in the ceiling, etc.  The moisture content of that outside air rises and falls and at this time of the year it is full of moisture - remember, warm air holds more moisture than cold air which is why the North & South Poles are the driest places on earth and the equatorial regions are the wettest.
 
We can only make our home inside living space dryer by dehumidifying it – which in theory means we would make the outside air more moist if we dumped that water outside.  We would need to dehumidify it 24 hours a day otherwise equilibrium takes us back to where we began with the inside the home air just as moisture laden as the outside air.
 
Unovent is unique in automatically stopping the air transfer into living spaces if the temperature in the roof space rises above 28 degrees celcius, but rarely at this time of the year does it switch off due to high outside moisture content (humidity) as it would in rainy winter conditions. This is because our UnoBrain is sensing “relative humidity” not “absolute humidity”.  We can be at as low as 20% relative humidity at a temperature of 45 degrees celcius in the roof space and as the temperature falls, the relative humidity rises to 60 to 70%.
 
It is important to note that a heat pump used in the summer months, when it is on cooling cycle, is an effective living space dehumidifier. The coil in the high-wall unit (inside the house on the wall) has the coolant passing through it which cools the air in the room passing over that coil.  As a result, the water condenses out of that air and runs outside through a drain tube.  Some people mistakenly have the understanding this happens in the winter making the house air dry and uncomfortable – it doesn't.  In the winter the high-wall coil gets hot which heats the air in the room passing over the coil.  The outside unit coil gets cold and water condenses out of the outside air to run out of the drain tube.

A home ventilation system is neither a dehumidifier or a heater. All brands simply bring fresh air in from outside the home to replace the stale air that is probably even more moisture laden as a result of breathing, showering, cooking, etc. A home ventilation system does help and we all know fresh air is healthier and helps to stop the growth of moulds and mildew which most people don't realise can be worse in summer than during winter.