Extractor Fans

An extractor fan removes moisture-laden air, odours, and airborne pollutants from a room and expels them to the outside, helping to maintain a healthy indoor environment. In kitchens, they remove cooking steam, grease particles, and food odours before they can settle on surfaces or penetrate furnishings. In bathrooms and wet rooms, they are essential for reducing humidity levels quickly after showering or bathing, which is the primary cause of mould growth and surface condensation. Building Regulations Part F requires adequate ventilation in habitable rooms, and extractor fans are the standard means of compliance in bathrooms and kitchens where natural ventilation is insufficient. They also play a role in reducing the risk of timber rot in floor joists and roof structures caused by prolonged moisture exposure within the building fabric. For trade installations, specifying the correct fan for each room type, duct run length, and airflow requirement is essential to achieve compliant and effective ventilation.

Bathroom extractor fans are sized by their airflow capacity, measured in litres per second (l/s) or cubic metres per hour (m³/h). Building Regulations Part F requires a minimum intermittent extract rate of 15 l/s (54 m³/h) for bathrooms. For a standard domestic bathroom this is achievable with a 100mm (4 inch) axial fan, which is the most widely installed size across residential and light commercial projects. Larger bathrooms, or those with longer duct runs exceeding two to three metres, may require a fan rated at 22 l/s or higher to compensate for resistance in the ductwork. Utility rooms and shower rooms have slightly different minimum requirements, so always check the specific room type against Part F tables before specifying. Where a fan incorporates a humidistat or timer overrun function, it can help achieve compliance without the need for continuous running.

Axial fans draw air through the unit in a straight line along the axis of the motor, making them compact and well-suited to short, direct duct runs where the external wall is close to the fan. They are the most common type for domestic bathroom and kitchen installations and are available in standard 100mm and 150mm sizes. Centrifugal fans use an impeller to draw air in axially and expel it at 90 degrees, generating significantly more static pressure — the ability to push air through longer or more complex duct runs with bends and multiple fittings. For back-to-back bathroom conversions, loft extensions, or commercial installations where the duct run exceeds three to four metres, a centrifugal fan is the correct specification to maintain adequate airflow. Axial fans will underperform on long or restrictive duct runs regardless of their rated output, leading to condensation problems and regulatory non-compliance. Choosing the correct fan type for the duct configuration is as important as selecting the correct flow rate.

Yes, extractor fans used for moisture and odour removal must always duct to the outside of the building to be effective and code-compliant. Venting into a loft space, ceiling void, or wall cavity is not permitted under Building Regulations and leads to condensation, mould, and structural damage in concealed spaces. The duct run should terminate through an external wall grille or a roof tile vent with a backdraught shutter to prevent cold air and pests from entering when the fan is not running. Flexible duct is commonly used for short runs and changes of direction, but rigid smooth-bore ducting gives significantly lower resistance and is preferable for any run longer than a metre or two. All duct joints should be taped and sealed to prevent moisture condensing and dripping inside the void. Ducting and vents are stocked alongside extractor fans at MP Moran, making it straightforward to specify the complete system in one order.

Bathroom zones are defined under BS 7671 and determine the minimum IP (Ingress Protection) rating required for electrical equipment in each area. Zone 1 covers the area directly above the bath or shower enclosure up to 2.25 metres and requires a minimum of IP44, meaning the fan is protected against water splashing from any direction. Zone 2 extends 0.6 metres horizontally beyond the bath or shower and also requires IP44 as a minimum. Outside the defined zones, standard IP20 fittings are technically permissible, but many installers specify IP44 throughout the bathroom as best practice to account for high ambient humidity. Ceiling-mounted extractor fans positioned directly above a shower require IP45 or higher. Always confirm the zone position of the proposed fan location before installation, as fitting a fan with an insufficient IP rating is a regulatory non-compliance that will fail an electrical inspection.

Both continuous and intermittent operation are valid approaches depending on the room type, building construction, and ventilation strategy. Intermittent fans switch on when the room is in use — typically triggered by the light switch — and run on for a timed overrun period of 10 to 20 minutes after the light is switched off, which is usually sufficient for a standard bathroom. Fans with a built-in humidistat are more intelligent, activating when relative humidity rises above a set threshold and switching off once the air has dried out, regardless of the light. Continuous low-rate fans run at a reduced background flow rate at all times and boost to a higher rate when triggered, which is increasingly favoured in airtight new-build properties where background ventilation is required under Part F. Choosing between these modes depends on the ventilation strategy for the building as a whole — in a leaky older property, intermittent operation is usually sufficient, while a well-insulated modern property often benefits from continuous low-rate ventilation to prevent overall moisture build-up.

Installing an extractor fan involves electrical work and is therefore subject to Part P of the Building Regulations, which governs domestic electrical installations. In England, most bathroom electrical work is classified as notifiable work, meaning it must either be carried out by a Part P registered electrician or self-certified by a competent person scheme member, or notified to Building Control for inspection. Replacing a like-for-like fan on an existing circuit with no changes to the wiring is generally lower risk and may fall outside notifiable thresholds in some interpretations, but adding a new circuit or installing a fan where none previously existed is clearly notifiable. For commercial projects, all electrical work must comply with BS 7671 and be inspected and tested by a competent person regardless of scope. From a practical standpoint, connecting to an existing fused spur or fan isolator is a straightforward task for a qualified electrician, but the ductwork run, hole-cutting, and external grille fitting are often the more time-consuming elements of the installation. Always check the certification requirements with your local authority or approved inspector before proceeding on any notifiable work.

Kitchen extractor fans are designed to handle higher volumes of air and, in the case of cooker hoods, to filter grease and cooking fumes before expelling air to the outside or recirculating it through a carbon filter. Building Regulations Part F requires a minimum extract rate of 30 l/s (108 m³/h) adjacent to a hob, or 60 l/s (216 m³/h) at ceiling level in a kitchen — significantly higher than the 15 l/s required for a bathroom. Cooker hoods mounted directly above the hob are the most effective solution for kitchens, removing steam and airborne grease particles at source before they spread into the room. Ceiling or wall-mounted kitchen fans are used where a hood is not practical, but require a higher airflow specification to compensate for the greater distance from the source of pollutants. Unlike bathroom fans, which primarily deal with humidity, kitchen fans must also handle grease-laden air, making filter maintenance and duct material selection more important. Appropriate ducting rated for kitchen use should always be specified, as grease deposits in standard flexible duct can become a fire risk over time.

Extractor fan noise is measured in decibels (dB) and varies considerably across models, from around 22 dB for premium ultra-quiet fans to 40 dB or more for high-output or budget units. For reference, 30 dB is approximately the level of a quiet library, and most people consider anything below 35 dB to be acceptably quiet in a domestic setting. Noise level is affected not just by the fan motor and blade design but also by the duct installation — poorly supported flexible duct, undersized grilles, and long runs with multiple bends all increase airborne noise. Fans mounted on rigid connections and with anti-vibration pads or rubber mountings will run more quietly than those hard-fixed directly to a ceiling or wall. For en-suite bathrooms or bedrooms where minimal noise is a priority, specifying a fan with a dB rating below 30 dB is worth the additional cost. Always cross-check the acoustic specification at the flow rate the fan will actually operate at, as some manufacturers quote noise figures at lower speeds than the rated operating point.

MP Moran stocks extractor fans from trusted brands including Vent-Axia, a British manufacturer with decades of experience producing compliant and reliable ventilation products for domestic and commercial applications. Our range covers bathroom fans, kitchen fans, and inline centrifugal fans to suit a wide variety of installation scenarios and duct configurations. Products are available online and across our six branches in London and Hertfordshire, with stock held locally for trade customers who need items quickly. Our ducting and vents range is stocked alongside fans so you can source everything needed for a complete ventilation system in one visit or order. Branch teams are trade-focused and can assist with specification queries, and electrical heating products are also available in the same department for projects requiring both heating and ventilation solutions. Visit your nearest branch or browse online to see the current range and availability.