Sub Floor Problems

Posted by in Subfloor on December 21, 2013 Comments off

Inadequate sub floor ventilation can cause many long term issues, a badly ventilated sub floor will become a breeding ground for mould which may lead to rotting and serious structural issues. This week Andy looks into sub floor ventilation.

The purpose of a underfloor ventilation system for your home is to extract the damp, humid air and to displace it with fresh air from and into the sub-floor area.

In some houses there is little underfloor ventilation, typical causes are:

  • There are very few or no vents.
  • Vents are often too small, inadequately sized or can become blocked over time.
  • There are vents on only one side – which can lead to ‘dead space’.
  • There are heating ducts or other obstacles that may block the air.

At Pure Ventilation we recommend fan assisted (mechanical) ventilation. This will help in most cases providing a few simple rules are followed. The most important factor to consider is ultimately you are looking to achieve a good cross flow of ventilation. So in a nutshell you want fresh air to be able to enter the sub floor area with the stale air being exhausted out, creating a cycle. Strategically placed passive inlet vents with an inline fan is usually the setup we recommend. At Pure Ventilation we make selecting the appropriate kit easy click here to view our full range of kits.

It is best to extract air from the sub floor as blowing in via a fan may result in some of the moist air getting into the house. It is best to run the fan during the day as the air is dryer and warmer and we usually recommend having the fan run for about 4 hours per day. Running costs are very low, based on operating for 4 hours per day every day your only looking at $10 – $60 per year depending on the type of fan used.

One option for subfloor fans is a low voltage (12V) fan. These fans can replace a vent (and some bricks) and they are ideal where there is no access to the under floor. They can take a short length of duct and can do smaller areas. The fan will need a transformer (included) which is connected to a power point.

The most powerful option is to use a centrifugal in-line fan. It can installed anywhere along the ducting and can be connected to a single inlet or to various inlets. This type of fan will move a large amount of air with long lengths of ducting and multiple vents connected to it.