The purpose of home ventilation system is to maintain a healthy living environment by supplying fresh air to your home while at the same time removing stale and humid air from habitable and subfloor areas.
The answer to effective subfloor ventilation is in the installation practices performed. Let us look at the sub-floor area itself. We can liken it to a blank canvas board as used by an artist. The more brush strokes, the more detailed and busy the canvas becomes.
When it comes to sub-floor or subfloor ventilation installation practices, the more materials that are used in the subfloor area the more inhibitive air flow becomes, as the air has to travel around obstacles
Let us look at the worse case scenario, that of plumbing systems (e.g. Bladder tanks for rainwater storage, drainage pipe work and central ducted heating). Ducting and pipe work range from 100mm to 300mm. When these ducts are installed, this could lead to sub-floor ventilation problems, as the air flow can be inhibited.
If the house is of solid brick construction, another subfloor ventilation obstacle exists, that of sub-walls. Ventilation companies are called in to rectify this problem by installing more flexible ducting and, in some cases, penetrate through these subwalls to accommodate the ductwork, ‘usually’ of 150mm or 6 inches, which means the penetration has to be larger to accommodate the duct itself. If they do not make these penetrations then they usually run the ductwork through an established opening under doorways. Therefore, we are still left with the legacy of the ductwork under the home, which inhibits sub-floor ventilation, as compared with Envirofan’s approach to subfloor ventilation installation practices.
Another consideration with the use of ducting in sub-floor ventilation situations is that in-line fans, as shown below, incur a back pressure drop as the air is pulled through the duct. Therefore, the efficiency of the in-line systems is marginally lost.
When sub-floor clearance are reduced in line with Australian Building Code guidelines at the minimum clearance of 300mm, installation of flexible ducting causing airflow obstructions may be unnecessary. Envirofan approaches this particular situation quite differently from orthodox subfloor ventilation methods.
Flexible duct has been used in the sub-floor ventilation industry for years. However, if alternative subfloor ventilation installation practices deliver a better result, should it not be considered?
At Envirofan , the sub-floor ventilation approach is cutting edge. When we start with a blank canvas, we finish with one. This is to maximise effective cross-flow in underfloor and sub-floor areas without obstructions.
Firstly, we can induce dry air from the outside and force it into the underfloor and sub-floor area by the use of solar-powered ventilation systems which are installed on the exterior wall (see pictures below) or by the utilisation of wire mesh vents. We then use brick size sub-floor ventilation systems that are established in the subwalls to direct air flow from room to room at a rate of 2.5m3/per minute at 27db, then extraction sub-floor ventilators are mounted on the exterior of the wall (see picture below) preferably on the east or southern aspects which draws the damp air out. This is the objective of what is deemed cross-flow ventilation. At Envirofan, the objective is to reach effective sub-floor ventilation. In exceptional circumstances, whereby there is no accessible exit point for an extraction system, the use of flexible duct to the nearest external point is unavoidable and is used sparingly.
So the conclusion is: for optimum effectiveness in sub-floor ventilation, keep your sub-floor clear and keep the use of flexible ducting to a minimum
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