Victorian Building Regulations designate Melbourne to be in a ‘Zone 3’ climate area, meaning requirements of subfloor ventilation to be 6-10 air changes per hour. This means that all air within the subfloor must be removed and replaced by fresh air 6-10 times per hour. In order to achieve this, regulations require ~6000mm2 of subfloor passive ventilation per lineal metre of external wall, with other things also considered such as decking etc. Rising damp, excessive moisture, buckled floor boards, mould and condensation are all symptoms of excessive moisture, often caused by a lack of ventilation to the subfloor area. Modern building regulations provide for passive ventilation which provides cross flow ventilation allowing the subfloor moisture to escape. Older houses are the ones which most often have ventilation issues in the subfloor which can lead to rising damp. In this instance, installing mechanical ventilation is often the answer.

Air expelled and air introduced:

Our ventilation systems are unique to the industry in-so-far as we install fans that both input fresh air and expel stale air. This provides a cycle of fresh air in and stale air out, providing the subfloor with the very best ventilation possible. All three (most systems are a minimum of three fans) fans are controlled by the one waterproof timer, meaning that the system runs automatically; no need to turn it on and off.

Subfloor ventilation procedure:

• Moisture tests —

We initially conduct a moisture test of the subfloor atmosphere and the subfloor soil. If we are drying the subfloor before installing fans we do before and after soil and atmosphere tests so we have something to measure the success of the ventilation from.

• Measure area to be ventilated —

The best types of ventilation systems are those that are ducted to all corners of the crawlspace or into every cavity (if the property is solid brick where each internal room is mirrored by a subfloor 'room' or area). If the access is sufficient to enable a ducted system to be installed, then the next step is to measure the area to be ventilated. The science of installing a subfloor ventilation system is a mathematical equation which is simply the cubic meterage of the crawlspace (width x length x height of crawlspace) divided by the output of the ventilation fans to be used. Our aim is always to go far beyond the VBA minimum of 6 airchanges per hour of operation, typically aiming for 18-20.

• Select the best and quietest fans —

There are a lot of different fans on the market. Our fans are sourced locally but manufactured in Europe, have a five year warranty and are the quietest fans on the market. The decibel output is important, for obvious reasons.

• Switching —

The fans are installed with either a 24-hour waterproof external timer (preset to run during daylight hours for a set period of time and adjustable) or via an hygrometer which turns itself on and off depending on humidity levels. The fans are generally set to run when occupants are not there and the times they run can be adjusted to suit.

• Inspect and re-adjust —

As part of our service, we will return to the property on a set date and check the moisture content of the crawl space and internal flooring and walls. Once we have established all moisture readings we will reset the timer up or down depending on the results we have achieved in the first month.