Incorrectly installed cooker hood ducting can have an adverse effect on the way a cooker hood performs so it is important to get this important feature right.
It is not always the fault of the cooker hood when odours and steam linger and there is too much operating noise. It can often be that the wrong size ducting or wrong configuration has been selected by either the installer or by the system designer.
Remember that the key aim in good ventilation installations is to move the air from its source to the outside of the house as efficiently and quietly as possible. The shorter the distance the air has to travel, the quicker and more efficiently it will get there. Obstacles such as bends slow the air down on its journey – so when bends are unavoidable, extra power may be needed.
Cooker hoods vary in power – and the more powerful the fan, the more important it is that the ducting is the right size for the job and has been installed in the most efficient way possible. In many cases the manufacturer’s guarantee will be invalidated if the correct size of ducting for the hood is not used. To avoid problems always choose the shortest and most direct route to the outside or the point where the air is to be released. Keep bends are kept to a minimum. Check the extraction capability and connection size of the hood and choose an appropriate size duct. Refer to the manufacturer’s spec for the model’s ratings. Never, ever reduce the ducting size. If the hood outlet is 150mm (6″) then the ducting must be of the same size.
Air travels better through a round duct, as it moves at a lower speed, resulting in less turbulence, vibration, noise and energy loss. However, the installation space available may prevent this ideal. A rigid duct is more efficient than a flexible duct and should be used whenever possible. If flexible hose is used, the hose should remain taut and as straight as possible. Special consideration should also be given to the selection of the wall terminal and the use of back draft dampers, as these also increase air resistance. Alaris are happy to offer technical advice.