What are the risks of poor sub-floor ventilation?
If the airflow is not adequate, the moisture level in the subfloor space will increase and timber will absorb additional moisture. As the EMC increases in timber, sapstain and mould fungi will begin to grow; this is particularly the case when the moisture level reaches around 18%. When timbers reach a moisture content of 20% decay fungi can grow which causes the timbers to rot and can lead to complete failure and collapse of the timber floor.
Termites & Moisture
Termites require high levels of moisture and damp subfloor areas are highly conducive to termite attack. Where very moist conditions are present, termites can devote all of their energies to attacking timber rather than bringing moisture in. Increased moisture levels are also conducive to attack by borers (wood boring beetles).
Other Indications & Issues
Damp under floor areas can create a number of problems within homes which include a damp or musty smell inside the home, mould and mildew growing on walls and ceilings, mould growth on leather goods such as shoes in built-in wardrobes.
It is generally accepted that a dry home is a healthier environment than a damp one. There is a general feeling of “wellbeing” in a dry home. There are a number of health issues that have been linked to living in a home that contains mould.
Ventilation of Subfloor Spaces
It is not uncommon for underfloor spaces to have insufficient ventilation. Ventilation can be improved by either passive or active ventilation. Passive ventilation utilises vents placed in the external wall of buildings. This may also require making openings in internal subfloor walls to ensure that a crossflow of air is achieved. Active ventilation involves fitting electrically powered fans and ducts that can be used to either push air into or, suck air from, a subfloor. These can then be attached to a timer so the hours of operation can be controlled.