315mm Polyethylene Vent column.

This option is only suitable for certain circumstances.

Normally used in highly treed low wind areas where other options will not work.  

Features.

No moving parts.

Nil Power requirement.

How does it work.

Air movement across the open top of the vent tube creates a negative pressure drawing air up the tube. Also sunlight on the tube heats the plastic causing the air inside to heat up causing the air to rise in the tube.  

Drawbacks

The tube is very large and visually very obvious. We recommend the top of the vent tube to be a minimum of a meter above the roof line to work most effectively. Consideration also needs to be given to the design of the structure to make the vent work most effectively.    Vents installed with the top outlet too low may not work at all and actually create a downward flow.