Extractor Hood Venting and Installation: UK Home Guide
Understand ducted versus recirculating extractor hoods, how to choose the right venting route, and what affects installation in a typical UK kitchen.
An extractor hood only works as well as its venting. A powerful hood that blows air into a closed duct, or recirculates through a worn filter, can be little better than no hood at all. Understanding the options before you buy saves a lot of frustration.
Ducted or recirculating?
Ducted extraction
A ducted hood moves cooking steam, grease and odours out of the house through a duct to an external wall or roof. It is generally the more effective way of removing moisture, which matters in modern well-sealed homes where condensation and mould are common concerns.
Recirculating extraction
A recirculating hood passes air through filters, then returns it to the room. It is simpler to fit where there is no route outside, such as in flats, but it does not remove moisture and relies on filters that need cleaning or replacing. Charcoal filters typically need replacing regularly, while metal grease filters can often be washed.
| Feature | Ducted | Recirculating |
|---|---|---|
| Removes moisture | Yes | No |
| Needs outside route | Yes | No |
| Running cost | Lower filter cost | Replacement filters needed |
| Installation | More involved | Simpler |
Planning the duct route
A shorter, straighter duct performs better. Each bend and each metre adds resistance. Some pointers:
- Use the duct diameter the hood specifies, and do not reduce it.
- Keep the run as short and straight as possible, with gentle bends rather than sharp elbows.
- Use smooth-walled rigid ducting where you can. Flexible ducting with ridges holds grease and reduces flow.
- Fit an external grille with a flap or damper to stop back-draught and pests.
- Seal joints so air and grease do not leak into ceiling voids.
- Slope any horizontal run slightly outwards so condensation does not run back into the hood.
Going through walls
Drilling an external wall needs the right tools and care about what is behind it, such as cables or pipes. A fitter or builder should handle masonry cores. Discuss with a qualified person if the route passes through a loft or chimney breast.
Positioning the hood
Manufacturers state the minimum height above the hob, typically for safety and performance. Gas hobs usually need more clearance than electric or induction. Following the manual matters because a hood hung too low risks heat damage, and too high loses capture.
Cooker hoods generally want an adjacent socket or fused connection spur. If one is needed, that is work for a registered electrician. Never extend the cable of a hood yourself.
Gas appliance considerations
Hoods used with a gas hob affect air supply and combustion. Any extraction fitted in a room with an open-flued appliance, such as a gas fire or boiler in the same space, needs professional advice. A Gas Safe registered engineer should check, because extraction can draw combustion gases back into the room.
Keeping it working
- Wash metal grease filters every month or two, depending on how much you fry.
- Replace charcoal filters on schedule.
- Wipe the grease trap and the visible duct parts occasionally.
- Use the hood while cooking and a few minutes afterwards.
Poor suction is usually due to saturated filters, a blocked external grille or a long, bendy duct. You can read more in related guides such as integrated vs freestanding appliances, which covers planning built-in kitchens.
Finding someone to fit it
Fitting involves electrics, ducting and sometimes masonry, so the right tradespeople vary. On Compito, you can describe the job, upload photos of the wall and ceiling and receive offers from ID-verified local providers. See our how it works page for the process.
Ducting options compared
| Duct type | Best for | Watch out for |
|---|---|---|
| Rigid round metal | Long runs, best airflow | Needs accurate cutting and joints sealed |
| Rigid rectangular flat channel | Tight spaces behind units | More joints and adaptors reduce flow |
| Flexible foil or plastic | Short temporary runs | Ridges trap grease and cut airflow |
Avoid using a smaller duct than the hood outlet, and avoid vent routes that end in a loft, soffit void or cavity wall, since the moisture will cause damp.
A worked example
Take a typical terraced kitchen where the hob sits on an internal wall. The hood is ducted to an outside wall 3 metres away with two 90 degree bends. That arrangement can cut the hood's real-world performance noticeably compared with its headline figure. Moving the hob location is rarely realistic, so the pragmatic fix is a short, smooth duct with gentle bends, or choosing a slightly higher-rated hood. Running costs are small either way, but poor airflow is the thing that is hard to live with.
Edge cases
- Flats and leasehold properties: drilling an external wall may need permission from the freeholder or management company.
- Rented homes: get written consent before cutting walls.
- Listed buildings or conservation areas: an external grille may need consent, so check before starting.
- Open-plan kitchens: a quiet hood with a high capture rate matters more, because the noise carries.
When to call a professional
Masonry cores, new electrical connections and anything touching a flue or gas supply are jobs for a suitably qualified person. Switch off at the supply before checking an existing hood.
Frequently asked questions
Can I fit a hood myself?
You can often hang the hood and run ducting yourself if you are confident, but the electrical connection and any masonry cutting are better left to qualified people.
How powerful does a hood need to be?
It depends on kitchen size and how you cook. The manufacturer's extraction rate relative to the room volume is a good indicator, but real performance falls with long ducts.
Why is my hood noisy?
Undersized ducting, a poor route or dirty filters make it work harder and louder. A quieter run often follows cleaning and a better duct layout.
Do I need to open a window when using a hood?
In a tight, well-sealed room, a hood can struggle to draw air if there is no way for replacement air to enter. A slightly open window can help.
Can I vent a hood into the loft?
No. Warm, greasy moist air in a loft causes damp and mould and can be a fire concern. A duct should end outside through a suitable grille.