Kitchen Ventilation Options: UK Part F, 30 L/s, and Ducting Pitfalls

For most remodels, a ducted hood that extracts to the outside beats recirculating hoods, downdraft units and whole-house extract. Approved Document F sets 30 l/s for a hood extracting outside, against 60 l/s with no outside-extract hood. Recirculation is the fallback when no duct route exists. Here is how to choose and fit the right one.

TL;DR:

• Use 150mm smooth rigid duct for standard runs; if flat channel is unavoidable, choose 220x90mm rather than 204x60mm, which cuts airflow.
• Check the manufacturer’s equivalent length limit, commonly 5 to 6m, and count bends, transitions, and grilles; a 3m run with four bends may approach it.
• Choose a hood at least as wide as the hob, and wider for an island, where no wall helps capture rising steam.
• Before the job is complete, have the installer commission the system, record airflow, and confirm that filters and ductwork remain accessible for cleaning.
• Condensation, lingering odors, grease film, or mold can signal poor extraction, but persistent wet walls may point to water intrusion or missing insulation instead.

Which kitchen ventilation options can you choose from?

Kitchen ventilation options fall into several families, and the right one depends mostly on whether you can get a duct to an outside wall.

Ducted range hoods pull steam, grease and combustion by-products away from the hob and send them outside. They come as under-cabinet units, wall-mounted chimney hoods and island hoods that hang from the ceiling. Wall and under-cabinet models usually have the shortest, simplest duct runs. Island hoods need a duct that travels up through the ceiling void, which takes more planning.

Recirculating (ductless) hoods pull air through a grease filter and a charcoal filter, then release it back into the room. They are easy to fit because no hole through the wall is needed. They trap grease and some odor, but they do not remove moisture or cooking pollutants from the home. Consumer Reports notes that vented hoods improve air quality more effectively, while recirculating models can be an option when venting outdoors is impossible.

Downdraft extractors rise from the worktop behind the hob, or sit on an island, and pull air downward. They suit open-plan layouts where an overhead hood would block sight lines. The trade-off is capture: a UK buying guide from Homebuilding points out that downdraft models are often less effective than overhead hoods at catching rising steam.

Standalone extractor fans and whole-house systems cover the rest. A wall or window fan suits a small kitchen without a hob hood. Mechanical extract (MEV) or heat recovery (MVHR) systems ventilate the whole home, with a kitchen extract point as one part of the design.

Here is how the options line up:

• Ducted hood: best for moisture and pollutant removal, needs a duct route
• Recirculating hood: easiest to fit, handles grease and odor only
• Downdraft: space-saving for islands, weaker capture
• Wall fan or whole-house extract: background ventilation, not a substitute for a hood over a busy hob

If you are rebuilding the kitchen, decide the ventilation route before the cabinets are ordered. A duct is far easier to hide behind a unit that has not been built yet.

What do the Building Regulations require for kitchen extraction?

Approved Document F is guidance for ventilation in dwellings. Check with your installer which requirements apply to your remodel. It asks kitchens to remove water vapor and pollutants at the source, supply outdoor air for occupants, and provide purge ventilation for fast airing. Extract can be natural, mechanical or a combination.

The numbers that matter most for a hob are the intermittent extract rates:

30 l/s where a cooker hood extracts to the outside, and 60 l/s where there is no hood or the hood does not extract outside. A properly ducted hood meets the requirement with half the airflow a bare fan would need.

The practical effect is plain. A recirculating-only hood does not satisfy Part F on its own, because the air never leaves the building. If you choose one, the room still needs a separate extract route that reaches the 60 l/s rate, such as a wall fan or a mechanical extract point.

The same guidance says extract terminals and fans, not including cooker hoods, should be fitted as high as practicable and no more than 400mm below the ceiling. Warm, moist air rises, so a high terminal catches it before it spreads.

Controls and proof matter too. The installer should confirm the relevant controls and commissioning requirements for your project, and explain what airflow records will be provided. The 2026 edition of the document repeats the extract rate tables and sets out the commissioning and documentation expectations, so ask your installer which version applies to your project and what paperwork you will receive.

Continuous extract options exist for kitchens in homes with whole-house systems. They run at a low background rate and boost when cooking starts. If your home already has MEV or MVHR, the hood and the central system need to be designed together rather than fitted separately.

How should you plan ducting and installation?

A hood is only as good as the duct behind it. We see the same mistakes on remodels again and again: a duct squeezed into a joist void, a reduced pipe size at the wall, or a run so long that the fan can never deliver its rated airflow.

Get the size right. 150mm rigid smooth-bore uPVC ducting is the common domestic specification for cooker hood extraction. Where space forces you into flat channel, the correct equivalent of a 150mm round duct is 220x90mm. The 204x60mm channel is the equivalent of 125mm, and fitting it to a 150mm hood cuts airflow noticeably.

Choose the material for the situation.

• Rigid uPVC suits standard runs
• Galvanized steel is the choice where the duct crosses a fire compartment
• Semi-rigid aluminum is acceptable only for very short transitions at the hood outlet
• Corrugated or flexible ducting should be avoided, because its ridges add resistance

Respect the equivalent length. Manufacturers specify a maximum, commonly around 5 to 6m for many domestic hoods. Every bend counts as extra length, as does every transition and external grille. A 3m run with four bends may already be close to the limit. Check the hood’s installation sheet and add up the bends before the duct route is fixed.

Finish at the outside end properly. A gravity flap terminal is usually the better choice because it closes when the fan is off and stops cold drafts and pests. Avoid reducers, fine mesh and decorative grilles that choke the outlet. Check the hood’s installation sheet and warranty terms for duct-size requirements.

Plan before you finish. Mark the duct route on the kitchen drawing before the units arrive. Check what lies behind the wall, whether the route passes through a joist and where the condensate is going to drain.

• Confirm the duct diameter matches the hood collar
• Calculate equivalent length including every bend
• Seal the joints and slope the duct slightly away from the hood where possible
• Keep access hatches for cleaning

Pro Tip: Photograph the duct route before the ceiling or wall is closed up. Years later, the picture will save you from guessing where it runs.

How do you choose hood capacity, size, filters and noise?

Rated airflow is the number everyone quotes, but capture decides how a hood performs in real cooking. A powerful fan over a narrow hood still lets steam escape around the edges.

Match airflow to your cooking. Quoted figures appear in cubic meters per hour or liters per second, so compare like with like. A hob used for daily frying and boiling asks more of a hood than one used for occasional meals. Aim for a model whose high setting comfortably exceeds the extract rate in Part F when ducted correctly.

Size the hood to the hob. Consumer Reports’ buying guide advises a hood at least as wide as the hob, and that guidance holds for UK kitchens too. Over an island, a wider hood gives better capture because there are no walls to channel the rising air.

Look for the right speeds. You need a strong setting for searing and boiling, plus a quiet low speed for the minutes after cooking. Variable speed control or a timed run-on is useful, because it lets the fan clear residual moisture without you standing by the controls.

Know your filters.

• Stainless steel baffle filters are washable and tough
• Aluminum mesh filters are cheaper and need frequent cleaning
• Charcoal filters sit in recirculating hoods and must be replaced, not washed

Check the noise. Compare decibel figures at the speeds you will actually use, and be wary of a single number quoted at the lowest speed. Better manufacturers publish tested sound levels. A hood that is loud at its useful speed will not be used, which defeats the purpose.

Lighting matters as well. Good hob lighting makes the hood easier to live with, and it is part of what the buying guide recommends comparing.

Where should you mount the hood, and what should your checklist include?

Follow the manufacturer’s stated height first. If it gives no height, consult the applicable guidance and ask your installer to confirm the mounting position. Too low is a heat and safety risk, and too high lets steam spread before the hood catches it. Confirm the hood is at least as wide as the hob, and remember that an island hood has no back wall to help with capture, so it benefits from extra width.

Before your installer signs the job off, confirm each of these:

1. The duct diameter matches the hood collar and the specified material
2. The equivalent length, including bends, falls under the manufacturer’s limit
3. The terminal is a gravity flap or another unrestricted outlet
4. The system has been commissioned and the airflow recorded
5. Filters and ducts can be reached for cleaning

How do you keep a kitchen extractor working well?

Clean or replace filters regularly, depending on how much you cook and which filter you have. Check the manufacturer’s instructions for how to clean baffle filters. Check the manufacturer’s instructions for whether charcoal filters can be cleaned or need replacing.

Plan for access when the system is installed. A hatch in the duct or a removable section makes cleaning straightforward, and in a heavily used kitchen the duct itself deserves periodic inspection, because built-up grease is a fire risk and slowly chokes the airflow.

Watch for warning signs that the system is falling short:

• Condensation on windows or cold walls after cooking
• Odors that linger for hours
• A film of grease on cabinets and ceilings
• Dark spots of mould appearing in corners or above the hob

Surfaces matter for upkeep too. Smooth, wipeable finishes at the ceiling line are easier to keep clean, and a guide to hygienic commercial coving shows how sealed edges resist grease build-up in busy kitchens.

Pro Tip: Put a reminder in your phone for filter cleaning on the first of each month. A hood with clogged filters moves far less air than its rating suggests.

Why ventilation decisions matter for damp and mould

In our survey work, kitchens with weak extraction show up often in the homes we are called to. Steam from boiling pans and kettles has to go somewhere. When it cannot leave through a ducted hood or fan, it condenses on the coldest surfaces, and that moisture feeds mould. Effective extraction can help remove moisture and cooking pollutants before they settle into the building.

Ventilation is one part of the picture, and it will not fix everything. If a kitchen wall stays wet after you extract properly, the cause may be water getting in from outside or missing insulation. Our Bournemouth kitchen case study shows a wall problem that needed diagnosis and targeted treatment, not a bigger fan. Our pages on condensation and moisture control and mould removal and air quality explain how we separate the two.

— Quay

What a complimentary survey from us covers

If your kitchen shows signs of damp, condensation or mould, we start with a complimentary survey, so the cause is identified before any work is proposed. Our in-house specialists carry out the diagnosis themselves, and you receive a detailed written report.

• A complimentary property survey that traces moisture to its source
• Ventilation, insulation or remedial treatment combined where your property needs it
• An insurance-backed guarantee on treatment work

Current prices are on our website. Book your survey or browse our full service range to see what we can do for your home.

FAQ

What are the different types of kitchen ventilation systems?

The main types are ducted range hoods, recirculating hoods, downdraft extractors, and wall or whole-house extract fans. Ducted hoods send air outside, while recirculating models filter it and return it to the room. Consumer Reports finds vented hoods more effective at removing pollutants.

What is the difference between a cooker hood and an extractor hood?

In UK usage the terms often overlap, but a cooker hood sits over the hob and captures cooking fumes at the source. An extractor hood usually means one that ducts air outside. Approved Document F treats a hood that extracts outside differently from one that only recirculates.

What are signs of poor ventilation in a kitchen?

Persistent condensation on windows or walls, lingering cooking smells, greasy film on surfaces and mould spots are the usual warning signs. Any of these suggest steam and pollutants are not leaving the room. A survey can show whether extraction, insulation or water ingress is responsible.

What is a Type 3 ventilation system?

Definitions of ventilation system types vary between guides, and we do not rely on a numbered label here. The practical question is whether the kitchen has extract that meets the Part F rate and exhausts outdoors. Your installer or a ventilation designer can confirm which system classification applies to your home.

Sources

• Approved Document F: Volume 1 applies to dwellings
• 150mm Rigid Ducting: The Correct Spec for Cooker Hood Extraction | BuildWiz UK
• 5 Best Range Hoods of 2026, Tested by Our Experts - Consumer Reports

Recommended

• PIV & Air Quality Solutions Dorset
• Penetrating Damp Kitchen Bournemouth