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Cross Flow Ventilation

Last Updated Dec 3, 2010 · Written by


Ventilation is an important consideration in all areas of the home, even the areas that you can’t see.  Read on to learn more about the role of cross flow ventilation.

Cross Flow Ventilation in the Sub Floor

Cross flow ventilation is where air flows from a supply point to an extraction point.  It is commonly used in sub-floor ventilation to remove trapped humidity that can encourage termites, dry rot in timber flooring structures, and an unhealthy environment within the home that can cause the occupants health problems.

For the best cross flow ventilation, it is ideal that the supply or induced air (the air from the supply point) comes from the drier northern or western aspects of the home, and is extracted via a ventilation system to the southern or eastern side of the home.

In line ventilation fan systems and ducting can be used but there are some issues to consider with this.  If the in line ventilation system has inadequate supply air, this can cause the system to overheat and burn out prematurely.  Supply air can also starve an in line sub floor ventilation system when the supply duct is too long or too small.  For this reason, it is vital that the ducting used is large enough to handle the air intake and that the ducts are of the correct length.  A ventilation specialist will be able to help with this.  There are also systems available that can actually eliminate ducting in the vast majority of cases.

Cross Flow Ventilation in the Home

Cross flow ventilation in the home ensures that there is sufficient fresh air entering the rooms of the home and that the stale air is extracted from the wet areas of the home.  Fresh air is supplied to the living rooms, working rooms, and bedrooms.  Each of these rooms has a supply air valve.  The used air is extracted from the kitchen, bathrooms, and other rooms with high indoor air pollutants through extraction valves.  This results in cross flow ventilation.  The fresh air enters the living areas where it flows through overflow zones into the wet rooms.  The wet rooms have a high ventilation rate, therefore ensuring that fresh air is best utilised.  Stale air is removed from overflow zones (such as wardrobes and hallways), and dehumidifies air in the wet areas.

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