Subfloor Ventilation Icon image with vents and air flowing

SubFloor Ventilation Systems, Costs and Solutions

Subfloor Ventilation Cost
DIY Subfloor Ventilation Installation

Your sub floor, also referred to as the under floor space, may seem insignificant because it does not form part of your living room. However, the fact of the matter is that this space actually has a high impact on the quality of air you breathe in while you are indoors.

Poor sub floor ventilation could lead to poor health for you and your loved ones. Additionally, it could cause damage to some parts of your home that are susceptible to decay caused by the development of mould due to high humidity levels in the house. We at Mouldbuster will do everything possible to eliminate the stale and moist air content and ensure that only fresh and dry air occupies that space.

Subfloor Ventilation showing air flowing in externally and flowing out through breathing vents on the sides of the house.

To achieve this, one of the following sub floor ventilation systems can be used:

Sub Floor Exhaust System

The logic behind the exhaust system is that a greater quantity of stale air is sucked out of the sub floor space than the fresh air that is blown into it. In order to achieve this, only one fan is dedicated to the supply of fresh air, while two are required for the expulsion of the stale air through vents. The two are referred to as exhaust fans.

Nature abhors vacuum. Automatically, the vacuum conditions created when the stale air is continuously sucked out of the sub floor will be filled by fresh air from outside. This is also enhanced by the negative pressure that exists in the sub floor due to the unequal movement of air. In the process of installing this system, the ventilation expert will determine the best place to vent out the damp air. This would typically be done through the lower part of the wall.

Sub-Floor Supply System

This sub floor ventilation system is the opposite of the exhaust system; instead of creating negative pressure, it creates positive pressure. A greater quantity of air is blown into the sub floor space, which will, as a result, force the damp, moist air out.

There are two supply fans that bring in the fresh and dry air from the outside, and only one exhaust fan that gets rid of the damp air. This is because the positive pressure will work to push out the damp air automatically. Some of the positive aspects of this system are:

  • It facilitates the drying up of damp or moist areas in the sub-floor area because dry air is constantly being blown over them. It is more effective than trying to force out the moist air from the damp surfaces.
  • It creates an effective way to manage the odors and moisture that exist in the sub floor area, where the damp air is redirected outside the home. Caution needs to be taken however, to ensure that the escape vent is sufficient for the damp air to leave the sub-floor. If this is not done, the dampness will end up rising into the home.

Balanced Pressure System

Quite different from both the exhaust and the supply systems, as the name suggests, there is a balance between the two fans that work in this sub floor ventilation system. One of them creates positive pressure, and brings dry and fresh air into the sub floor space. The other one works using negative pressure and expels the same amount of stale or moist air from the under floor. It is balanced because the speed at which the air moves into and out of the sub-floor is the same.

There are some noteworthy advantages of this system:

  • Damp surfaces will eventually be dried up through the expulsion of moist air from the damp surfaces and the subsequent dry air that is blown over them
  • The management of the stale smells and dampness is effective since the installation of the outlet through which this air is expelled is determined by you
  • The entire sub floor area will be managed by the system because the entry point of fresh air into the sub-floor is at the extreme opposite of the exit point of damp air

Infographic: Sub floor Ventilation Infographic discussing underfloor Balanced Pressure System, Exhaust System and Supply System.

Sub Floor Ventilation : Other Considerations

Each of the sub-floor ventilation systems needs fans with a specific design, shape and size. The kind of fan you will select depends on how big or small your under floor area is. It will also depend on the materials which your house is made from, e.g. timber.

Fans usually have either the AC or EC motor. The AC fans are set to run at one speed only, but are not noisy when running. On the other hand, EC fans have different speeds and are more efficient and less noisy than AC fans.

The sub floor ventilation system should run during the day. This is because the quality of atmospheric air is better during the day than at night. Air is drier during the day and the system’s noise will not be easily heard over typical daytime activities.

Once the installation of the sub floor ventilation system is done, the high humidity levels in the under floor air will only be brought to negligible levels after the system has run for twelve hours.  After this initial set up and run time, you won’t need it to go on for such long hours. Four hours per day will be sufficient to keep the underfloor ventilation at its best, making the sub floor space both fresh and moist-free.

Sub Floor Ventilation Cost

A quality system for an averaged sized home should be around $2500 supplied, installed, including GST and 5 years warranty.

Sure.  Talk to us about supplying a sub floor ventilation kit.

We service homes and businesses in states all over Australia, including the New South Wales, Queensland, Australian Capital Territory, Victoria, Tasmania, South Australia, Western Australia and Northern Territory.

Capital cities include, Sydney, Canberra, Melbourne, Hobart, Brisbane, Adelaide, Perth and Darwin.

Contact the ventilation experts, Mouldbuster on 1300 066 853 for the best advice on sub floor ventilation services and your best options based on your budget.