Subfloor Ventilation is the key to a healthy subfloor and therefore a healthy house.
In brick houses and especially older brick houses, there is typically too little natural subfloor ventilation in the crawlspace. When coupled with the older brick or bluestone footings - which decree that each room in the dwelling is mirrored with the same chamber in the void beneath the house - there is both no natural ventilation of this crawlspace area and no cross flow ventilation. In these instances the only way of improving crawlspace ventilation is to install mechanical subfloor ventilation.
Generally speaking, people will notice when they have a poorly ventilated subfloor (and therefore a damp crawlspace) by the presence of a damp, mildew or musty odour. Further investigation may reveal the presence of fungal growth on both the soil and any brick footings. In more extreme cases evidence of rising damp, brick and mortar deterioration is very common.
Once the symptoms are apparent, then mechanical subfloor ventilation of the crawlspace is generally required.
Once it has been determined that the subfloor requires ventilation (by the presence of long term moisture, fungal growth, rising damp deterioration to brick foundations, etc.) the process for installing a subfloor ventilation system is as follows.
We initially conduct a moisture test of the subfloor atmosphere and the subfloor soil directly from the crawlspace. 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.
Obviously access to the crawlspace and the structure of the crawlspace is important.
There are a lot of different fans on the market. One of our competitors calls them air pumps but they are in fact fans. Our ventilation fans are sourced locally but manufactured in Europe, have a five year warranty and are the quietest fans on the market (Technical specifications for our Quiet Subfloor fans). The decibel output is important, for obvious reasons.
Our fans are all mounted on a chipboard base with a 20mm rubber barrier installed between the fan and the particle board base. They are then either screwed onto the joists or mounted on the floor of the void. The ducting is run to every cavity in the subfloor and the fans are balanced in the subfloor (subject to access) so that they are evenly distributed to allow an even spread of air throughout the subfloor.
The fans are installed with either a 24 hour waterproof timer (pre set 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.
As part of our service, we will return to the property on a set date and check the moisture content of the crawlspace 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.
Rising damp, excessive moisture, buckled floor boards, mould, condensation are all symptoms of excessive moisture, often caused by a lack of ventilation.
The presence of moisture in the crawlspace does not of itself mean that a permanent mechanical ventilation system is required. If the reason for the moisture is preventable and/or caused by an event which is controllable, then a ventilation system may not be necessary.
If however, the problem is caused by structural issues - a permanent lack of ventilation which can only be overcome by mechanical intervention - then it will be necessary to install a permanent mechanical ventilation system which will stabilise the subfloor atmosphere so that moisture will not enter the living areas and mould will not grow. Subfloors must be ventilated one way or the other to ensure that moisture which is naturally inherent in soil can escape from the subfloor crawlspace. 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.
Our "Air expelled and air introduced ventilation systems" are unique to the industry in so far as we install fans that both input 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.