Fitting an Extractor Fan: A Step-by-Step Guide

Authored by Ollie Lyon on Wednesday 10th February 2021, revised on Wednesday 2nd February 2022. When it comes to keeping the bathroom well-ventilated, simply cracking open a window doesn't cut it - an extractor fan is necessary.

But what exactly are extractor fans and how do they operate? More importantly, how does one go about installing an extractor fan? Plumbworld has compiled this comprehensive guide to assist you in understanding how to install a fan on either your bathroom wall or ceiling in order to enhance ventilation.

Furthermore, we will discuss the reasons why an extractor fan may be required in your bathroom, which go beyond steam and odors. We will carefully walk you through the step-by-step installation process and address the essential questions pertaining to fitting an extractor fan.

Continue reading to explore more about extractor fans and how to incorporate them into your bathroom...

What precisely are extractor fans? Essentially, an extractor fan demolishes moisture within your bathroom and is a crucial component for maintaining a fresh-looking bathroom.

Why is there a need for an extractor fan? By effectively eliminating moisture from the air, a bathroom exhaust fan prevents the growth of mold in your bathroom. Mold and mildew thrive in warm and damp environments, such as behind your toilet, basin, bathroom furniture, or tiles, therefore it is vital to ensure proper ventilation within your bathroom.

Learn more: How to Eradicate Bathroom Mold

Using an extractor fan during or after taking a shower or bath, depending on the airflow in your home, aids in removing moisture from the air. Even when the fan is operational, it is important to remember to leave the door open when the bathroom is not in use and to open a window to maintain adequate ventilation.

The Guidelines for Bathroom Ventilation Regulations

In the United Kingdom, the regulations concerning the necessary level of ventilation in your bathroom can be found in the document known as Building Regulations Document F. If you wish to explore the entire document, you can access it through this link. However, we have condensed the vital information below for your convenience.

• In the UK, it is obligatory for a bathroom to have either a window or an extractor fan for ventilation purposes.
• If your bathroom consists solely of a toilet, a window is sufficient as your source of ventilation.
• In newly constructed bathrooms with both a bath and a shower, mechanical ventilation is required in the form of an extractor fan. This necessity arises from the fact that these new constructions are designed to be more airtight, resulting in significantly reduced natural ventilation.
• The ventilation standards for a bathroom dictate a requirement of 15 liters per second or 54 cubic meters per hour.

The last point denotes that the measurement of 15l/s or 54m3/hr indicates the volume of fresh air that replaces the stale air in the bathroom.

Varieties of Extractor Fans

When considering the different types of extractor fans, three common configurations exist, which are described in detail below:

• Ceiling fans that pass through the roof eaves and vent out through an external wall.
• Wall fans that directly duct air through to an external vent.
• Fans installed in glass windows.

Out of these three configurations, the first two are the most commonly used and easiest to install. Importantly, each configuration has specific names. A ceiling fan is termed either "inline" or a "centrifugal fan." Although the two operate differently, a wall fan is referred to as an "axial" fan, and we have provided more information about each type below.

• Axial fans: These fans directly connect to an external wall and are suitable when air movement over long distances is not required.
• Centrifugal fans: Typically installed in the ceiling, these fans are designed for bathrooms located over 1.5m away from an external wall.
• Inline fans: Generally fitted in the ceiling, these fans can be utilized for extra-long ducting distances of up to 40 meters.

Determining the Correct Size of an Extractor Fan

To determine the appropriate size of the bathroom extractor fan that you require, you need to calculate its extraction rate. This figure indicates the amount of air that can be expelled from a room within one hour and is measured in cubic meters per hour.

To achieve the extraction rate calculation, you must measure the dimensions of your bathroom using a tape measure and record the height, width, and length of the room in meters. Upon obtaining these measurements, multiply the three figures together to determine the size in cubic meters.

Further reading: All-Inclusive Guide to Bathroom Ventilation

The extraction rate required for your bathroom depends on its size. Nevertheless, in accordance with building regulations, if your bathroom does not have an operable window, the minimum fan extraction rate that you should meet is 54 cubic meters per hour (or 15 liters per second). Therefore, ensure that you comply with this minimum requirement.

Pro Tip: To calculate the liters per second (l/s), divide your cubic meter measurement by 3.6. This is because approximately 3.6 cubic meters is equal to 1 liter per second.

What is the cost of extractor fans?

The price of an extractor fan varies depending on whether it is a new installation or a replacement. Additionally, you should also take into consideration the cost of installation. The average cost of replacing an existing fan, including installation, is £175. However, if you are installing a new fan, the cost can be around £300.

How to install a ceiling extractor fan

Essential Tools

• Flexible ducting
• Saw
• Grill cover and fittings
• Drill with the appropriate drill bit
• Pad saw
• Stepladder
• Screwdriver
• Safety equipment
• Pencil

The Procedure

1. Plan: Ensure that there is sufficient space in the attic for the fan. When cutting through the ceiling, always make the incision between the horizontal support beams. Additionally, employ an electronic detector to check for any concealed wiring or plumbing.

2. Create an opening in the ceiling: If installing a new extractor fan in a different location, select the desired placement and remove any insulation.

3. Mark the position of the fan vent on the ceiling using a pencil. Drill a hole through the ceiling on the marked spot. Use a pad saw to cut along the outline and carefully remove any excess material.

4. Mount the vent on the ceiling: Attach the fittings to the vent, which will secure it to the duct pipe in the attic. Once attached, position the vent over the opening and mark the spot for the holes that will secure it to the ceiling.

5. Drill holes on the marked spots and insert appropriate fittings, such as wall plugs. Hold the vent in place and fasten it securely using a screwdriver. Be aware that the correct type of fixings may vary depending on your ceiling.

6. Install the fan in the attic: Depending on the design, the fan should be secured horizontally to the floor or the attic side of the ceiling. Use a pencil to mark the attachment points on the fan frame, then proceed to drill holes. Insert the fittings as required and use a screwdriver to secure the frame in place.

7. Connect the ducting: Secure the flexible ducting to the ceiling vent and one side of the extractor fan. Attach another piece of ducting to the opposite side of the fan, which connects to the external ventilation source.

8. Complete the electrical connections: All electrical work should be undertaken by a qualified electrician. Depending on the fan, it can either be operated by a separate control or connected to the light switch. Once the electrical connections are made, fit the grill cover over the vent on the bathroom ceiling.

9. Once you are confident in the installation of the extractor fan, replace any insulation in the attic.

How to install a wall-mounted extractor fan

Required Tools

• Flexible ducting
• Saw
• Grill covers and fittings
• Drill with appropriate drill bit
• Hammer
• Chisel
• Screwdriver
• Tape measurer
• Safety equipment
• Pencil

The Process

1. Plan for your fan installation: Employ a pipe and cable detector to identify any hidden pipes or cables. Ensure that there are no obstructing pipes on the external wall where you plan to install the fan. Moreover, make sure that the outlet is not positioned directly beneath a window.

2. Create an opening: When installing a fan in a new location, you must create an opening in the wall. After confirming that the wall is clear, position the fan in place and use a pencil to trace along the circular edge. Mark the center point on the wall and drill a hole as a reference.

Remember to always prioritize safety and consult professionals when necessary.

3. Next, begin by creating a sequence of openings surrounding the circular outline of your fan, ensuring they are approximately 35mm apart. Once this task is completed, proceed to utilize a chisel and hammer to extract the designated section of the wall.

4. Integrate the ducting: Following the establishment of the opening, skillfully insert the flexible ducting. It should be positioned at a slightly angled downward position and remain flush against both the inner and outer wall surfaces. If necessary, make any necessary adjustments by trimming the ducting with a saw.

Tip: Should any repairs to the wall's plasterwork be required around the drilled area, now is the ideal moment to address this issue.

5. Install the fan: Begin by securely affixing the fan onto the interior wall, utilizing a pencil to ensure proper alignment. Proceed to drill holes at the designated positions in order to insert the required fittings. Once complete, position the fan over the drilled holes and firmly secure it in place using a screwdriver.

6. Repeat the same process for the exterior wall.

7. Create the electrical connections: Similar to the installation of a ceiling fan, a certified electrician must be responsible for executing the appropriate electrical connections. Depending on the specific type of fan, it may be operated through a separate control mechanism or by utilizing the existing light switch.

8. Once the electrical connections have been successfully established, proceed to attach the grille covers to both the interior and exterior sides of the fan. In the case of grilles with slatted designs, ensure they are positioned horizontally to effectively prevent rain infiltration.

Instilling a shower within your bathroom encompasses more than the mere combination of a shower unit and enclosure. A crucial component in this process is fitting the shower tray, and Plumbworld is readily available to offer guidance and assistance.

Ollie Lyon

Ollie is a self-taught DIY enthusiast with a particular passion for kitchen and bathroom renovations. During his free time, Ollie finds enjoyment in cycling and hiking.

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