Ducting for Cooker Hoods

When planning a new cooker hood installation, it is important to understand how the ducting can affect the performance of the hood. In simple terms, longer ducting, more bends and even the type of duct can significantly affect the air flow and noise level of an installation.

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Building regulations stipulate that a kitchen extractor should have an air flow of 60 litres per minute or 3.6 cubic metres per hour. But when redesigning a kitchen, cooking areas are often relocated from their ideal location (such as a kitchen external wall) to a more challenging position in an island of units at the centre of a kitchen space.

As a result the ducting, which previously may have gone directly through the wall and been less than 500mm long, may now require fitting into the roof space, entailing several bends to change direction and being four or five metres in length before the air can be discharged from the building.

To counteract loss in performance, manufacturers observe the effect of ducting on their products and will normally give a recommendation of what ducting length the hood is designed to operate within. The figure quoted by the cooker hood may be "a maximum duct length of two metres using 150mm duct work". This figures assumes a rigid, smooth-walled duct work, however if ducting with a corrugated wall surface is used this will reduce its performance.

If your hood is connected to longer or narrower ducting it may be possible to add an extra inline fan motor to help push the air through the ducting. When installed correctly a cooker hood will usually draw air flow sufficient to keep a piece of A4 paper attached to the filter screen, even when on the slow setting.

For further information on the effect of ducting in performance, please follow this link

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* All information provided is a guide only. BuySpares accepts no liability for any problems occurred while attempting any advice shown. If in any doubt contact a qualified repair service.