Question 1

What extract rate does a UK kitchen cooker hood need?

Accepted Answer

Per Approved Document F 2021 Table 5.1a, a kitchen intermittent extract positioned adjacent to the hob (i.e. a ducted cooker hood) requires 30 L/s (108 m³/h). If extract is sited elsewhere in the kitchen (no hood over the hob), the rate rises to 60 L/s (216 m³/h). The continuous-extract alternative is 13 L/s. Commercial kitchens typically need 120+ L/s depending on cooking intensity. A recirculating hood only filters odour/grease and does not extract to the outside, so under ADF it falls into the "elsewhere" row — a separate 60 L/s intermittent extract is still required.

Question 2

Should I choose a ducted or recirculating cooker hood?

Accepted Answer

Ducted hoods are far more effective as they remove moisture, odours, and combustion gases (from gas hobs) directly to outside. Recirculating hoods only filter odour and grease — they cannot remove moisture or CO/CO2 from gas combustion. ADF guidance strongly favours ducted extraction, especially for gas cooking. Recirculating hoods may not satisfy Part F for gas hobs.

Question 3

What size duct do I need for a cooker hood?

Accepted Answer

A minimum 150mm diameter rigid duct is recommended for domestic cooker hoods. For longer runs (over 5m) or multiple bends, 200mm diameter reduces pressure drop and noise. Never reduce below 100mm. Use rigid galvanised or plastic duct — avoid flexible duct for long runs as it has 3-5x higher friction loss.

Question 4

Does a cooker hood need make-up air?

Accepted Answer

Yes, ducted cooker hoods extracting 30 L/s or more create measurable negative pressure, and any boost rate above ~50 L/s can affect open-flue appliances. Replacement (make-up) air must enter the kitchen through trickle vents, background ventilators, or a dedicated make-up air supply. Without adequate make-up air, the hood cannot achieve its rated flow rate, doors may slam, and back-draughting of flues can occur.

Question 5

How wide should a cooker hood be?

Accepted Answer

The hood should be at least as wide as the cooker, ideally 50-100mm wider on each side for better capture. A 600mm cooker needs a 600-800mm hood. A 900mm range cooker needs a 900-1000mm hood. The bottom of the hood should be 650-750mm above the cooker surface for optimal capture without head clearance issues.

Kitchen Cooker Hood Calculator — Extract Rate & Ductwork

How We Calculate This

ADF 2021 Table 5.1a extract rates

Ductwork guidance

Frequently Asked Questions

Related Calculators

Extract Fan Sizing Calculator

Ductwork Sizing Calculator

Duct Pressure Drop Calculator

Air Change Rate Calculator

Kitchen Extraction Calculator