The Cooker Hood Conundrum: Will Yours Meet the Regulations?

Andrew Nash, Residential Business Development Manager

Filters

Most residential new-build properties include a cooker hood over the hob. It's the accepted 'norm'. It comes as part of the Kitchen Fit-out package in a house or apartment build and its specification is usually dictated by form not function!

Modern cooker hoods can be set-up to either re-circulate air through grease and carbon filters, returning the filtered air to the room, or exhaust via a short duct run to atmosphere.

The cooker hood straddles the line between a domestic appliance and a piece of ventilation equipment. Used as a re-circulating hood where air is returned to the room it does not satisfy either Part F of the Building Regulations or the Domestic Ventilation Compliance Guide as a kitchen extract fan. In this mode it's just a domestic appliance.

Used as an extract hood with its own exhaust duct it has the capacity to unbalance a balanced whole house MVHR system! Modern buildings are so well sealed that the cooker hood literally fights with the MVHR system as its ducts are a far easier air-path than infiltration.

They rarely (if ever) have the facility to integrate with a home automation system or control system of any description so cannot be tied into the operation of other ventilation equipment.

The ideal scenario is to treat the  hood as an entirely separate, occupant operated, filtered recirculation device to capture grease and reduce cooking smells whilst the Continuous Mechanical extract system (MEV), or MVHR system operates in the background to ventilate the property as Part F intended.

The worst scenario possible is to duct the extractor hood in series with the MVHR or MEV. A non-running extractor hood or one with dirty filters provides high resistance on the kitchen leg, preventing the central ventilation system from extracting the correct amount of air from the kitchen. A running, high air-flow extractor hood pushes more air into the central system than it can extract away, resulting in kitchen smells being blown back down the extract ducts into other wet rooms!

If you or your client decide you absolutely must have a  kitchen extract hood in addition to an MVHR/MEV system then your only option is to use a hood with a filter, light and boost switch but no fan. These do exist!

The filtered hood can be mounted above the cooker in the normal way and ducted direct to either system. The switch is wired back to the MEV/MVHR taking the unit to boost when required. Occupant control is far less confusing and correct ventilation rates are assured.

 

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