What This Requirement Covers
The kitchen is the primary source of moisture, odours, and airborne pollutants in a dwelling. Approved Document F requires adequate extract ventilation from all kitchens to maintain indoor air quality and prevent condensation.
Key Requirements
Extract Rates
- Cooker hood (adjacent to hob): 30 litres/second minimum extract rate, ducted to outside
- General kitchen extract fan (not adjacent to hob): 13 litres/second minimum
- Continuous extract (System 3 or 4): Minimum whole-dwelling rate with boost capability to 13 l/s in the kitchen
Cooker Hood Types
- Ducted hoods: Extract cooking fumes and moisture directly to outside through ductwork; the most effective option and required by Part F
- Recirculating hoods: Filter the air and return it to the kitchen; do not remove moisture and are not acceptable as the sole means of kitchen extract ventilation under Part F
- Downdraft extractors: Extract at hob level; must be ducted to outside and achieve the minimum flow rate
Ductwork
- Kitchen extract ductwork must terminate to outside (not into a loft, soffit, or cavity)
- Ductwork should be as short and straight as possible
- Rigid ductwork is preferred; flexible duct has higher resistance and should be limited to short connections
- Ductwork diameter: Minimum 100 mm for cooker hoods (150 mm preferred for longer runs)
- The external terminal must have a backdraught damper to prevent cold air entering when the fan is off
Practical Compliance Tips
- Always duct cooker hoods to outside; a recirculating hood does not meet Part F requirements
- Use rigid ductwork for the main run and limit flexible duct to the connection at the hood
- Keep duct runs short; every metre of duct and every bend reduces the effective extract rate
- Clean cooker hood grease filters regularly (monthly for heavy use); blocked filters reduce airflow significantly
- Ensure the external terminal is positioned away from windows and air intakes (minimum 300 mm clearance)
- If the kitchen is open-plan to a living area, the extract rate must still meet the kitchen requirement
- Provide a make-up air path (trickle vents or a dedicated air inlet) to replace the extracted air