Roof Ducting Kit
Roof ducting is the most efficient means of removing cooking fumes to the outside. Straight up with no obstacles or bends, there’s nothing to cause back pressure or impede airflow. Use only rigid or semi-rigid ducting for this installation as the use of flexible duct will reduce efficiency and increase noise.
As always, the quality of ducting is important to ensure the rangehood performs as it should and that noise is kept to a minimum. Ducting that disrupts the airflow will cause noise and reduce performance. Ducting that prevents the back-draft flaps from rising properly will restrict the airflow, strain the fan motor and increase noise.
A roof ducting kit will consist of lengths 0f galvanised steel and and a roof cowl. For installations where the duct has to go around rafters or purlins, semi-rigid duct may be used. Be sure to use a roof cowl that’s made for the job, i.e. accepting fast moving air under pressure. Too often a wall roof cowl that was designed to reduce downdraft for fires is offered. This design, on the left below is intended for slow moving fire smoke. The apex shape causes a high pressure area to build up and impede air flow from rangehoods. The design on the right, or similar, is most efficient for rangehoods so avoid the downdraft cowl for your roof ducting installation.
Anti-downdraft Roof Cowl Rangehood Roof Cowl
Kitchen ventilation advice for New Zealand kitchens
Copyright Tom McKernan 2017