Extractor Fan: Step-by-Step Installation Guide for Bathrooms

A bathroom extractor fan plays a vital role in keeping your bathroom fresh and comfortable. It removes humid air, prevents mold, and helps eliminate lingering odors. Designers used natural airflow for centuries, but mechanical ventilation gained popularity in the 19th century. Today, home construction usually includes some form of bath fan to protect indoor air quality. As urban areas expand, more homeowners install these systems in new and existing buildings. Smart home projects also drive this trend, as people want automated systems that keep living spaces healthy.

Before we go any further, I want to clear up some confusion I’ve seen over the years when it comes to ventilation. Many homeowners assume that all vent fans work the same way, but there are some important differences between an extractor fan and exhaust fan.

  • Extractor fan – This is the type most commonly used in bathrooms. It specifically removes moisture and odors by pulling humid air out of the room and venting it outside.
  • Exhaust fan – Functions on a more powerful system designed for high-humidity levels or commercial spaces.

For bathroom ventilation, an extractor fan is what you need to effectively remove moisture and prevent mould.

Why You Need a Bathroom Air Vent

Many bathrooms need an extractor fan or any type of vent fan if there’s no window that opens. Even with a window, a bathroom ventilation fan quickly clears out humidity, which can otherwise lead to mold, wood rot, or peeling paint. Installing a fan lets you direct the moist air outside instead of letting it linger. You can also choose a model with added features, like a built-in heater or overhead light. This often requires installing a double switch so you can manage each function separately.

Choosing the Right Extractor Fan

  • Pick an extractor fan rated to clear the room’s air in about five minutes.
  • Spending a bit more on a quality fan usually means less noise.
  • Some models include lights, heaters, or motion sensors for more versatility.

If you need help deciding, our in-depth guide on bathroom ventilation tips covers everything from fan capacity to choosing the best style for your space. And if you’re unsure which fan to choose, you can browse a range of bathroom extractor fan kits here.

An efficient ventilator fan for bathroom installation.

Planning the Installation of the Extractor Fan

Before installing a bathroom ventilation fan, check local building codes to ensure compliance. In the UK, ventilation must meet the requirements outlined in Approved Document F, which covers airflow rates and proper venting methods.

Then make sure you have access to the ceiling or an attic space above, along with a clear path for the duct. Some fans exit through the roof, while others can vent through a sidewall or soffit. You should confirm that the path is short and insulated, especially in cold climates, to prevent condensation. This planning includes finding the best spot to capture humidity near showers or bathtubs, ensuring an airtight connection, and checking vent fan wiring requirements. If the existing circuit can’t handle a motor, you might need a new supply line from the electrical panel.

Everything You Need to Install an Extractor Fan

  • Drill/Driver with extended spade bit (3/8-inch) and a 4 to 4½-inch hole saw
  • Jigsaw (or reciprocating saw)
  • Screwdrivers (Phillips and flathead)
  • Measuring tape and pencil
  • Layout or framing square
  • Safety goggles, gloves, and possibly a respirator
  • Ladder or step stool for accessing the ceiling or attic
  • Caulk gun, foil duct tape, and exterior caulk
  • Electrical cable, wire connectors, and any needed switches
  • Ductwork (insulated if required by local climate)
  • Roof vent or wall cap (for outside venting)

A set of essential tools, including a drill, gloves, and safety goggles.

DIY or Hire a Professional?

Some homeowners manage this project themselves, especially when replacing an old extractor fan. However, installing a new vent often involves running wires, cutting siding or roofing, and sealing ductwork. If you’re unsure about vent fan wiring or modifying your home’s structure, consider hiring a professional. A licensed electrician can calculate circuit loads, confirm breaker capacity, and handle a new feed if needed. This approach improves safety and may protect your insurance coverage if issues arise later.

How to Install a Bathroom Ceiling Extractor Fan

However, if you have experience with home renovations, electrical work, and basic carpentry and the right tools, you might be able to work on this project yourself. That said, installing an air ventilation fan involves cutting through ceilings or walls, routing ductwork and handling wiring. So if any of that sounds unfamiliar, hiring a professional can save time and prevent costly mistakes. 

Choose the Right Fan (CFM and Sone Rating)

Bathroom fans are rated by two main factors: cubic feet per minute (CFM) and sones.

  • CFM measures how much air the fan moves in one minute. A quick way to size your fan: multiply the bathroom’s square footage by 1.1. For a 100-square-foot bath, choose a fan rated around 110 CFM.
  • Sones measure sound. A lower number means a quieter fan. A modern refrigerator runs at about one sone. Many bathroom fans range from 0.5 up to 6.0 sones.

Plan Your Route and Prepare

If you have an attic above, you can run the vent through the roof or an exterior wall. In a basement, you may need to run it through a rim joist or foundation. You’ll need a drill with a long spade bit, a drywall or jigsaw, proper extractor fan ducting, like foil duct tape (not cloth tape), a length of flexible or rigid duct, the fan housing, and mounting brackets.

A worker planning the ducting route in an attic.

Mark and Cut the Ceiling (Attic Installation Example)

  • Mark the ceiling where you want the fan (usually between the shower and toilet). Drill a hole with a long spade bit. Go into the attic and locate this hole. Clear insulation around it so you can see nearby pipes or obstructions.
  • Measure the inside dimensions of the fan’s intake port. Transfer those measurements to the ceiling using the reference hole as a guide. Draw a rectangle with a framing square or layout square.
  • Wear goggles and a respirator. Use a jigsaw, reciprocating saw, or drywall saw to cut along the marked lines. Support the waste piece before finishing the final cut, so it doesn’t tear the surrounding ceiling.

A power drill cutting a ceiling hole for a bathroom ceiling extractor fan.

Position the Extractor Fan Housing

  • In the attic, attach a 4-inch 90-degree elbow (if needed) to the fan’s outlet port. Secure it with foil duct tape, which won’t degrade over time.
  • Slide the fan’s metal brackets into the side tabs. Center the fan over the hole in the ceiling, ensuring it clears any joists or pipes.
  • Extend the fan’s brackets until they touch the joists. Secure them with 1½-inch drywall screws.

Connect the Duct and Wiring

  • Slip one end of the flexible or rigid duct over the fan’s outlet elbow. Secure with a gear clamp or foil duct tape.
  • Remove the knockout on the fan housing. Install a cable connector and feed the electrical cable through. Tighten the connector screw to hold the cable.

A worker connecting the ductwork to the ventilation system, securing the flexible duct for optimal air vent performance.

Vent Through an Exterior Wall (If Not Going Through the Roof)

  • From inside the attic, pick a spot between studs within 6 feet of the fan. Note measurements from a nearby window or soffit to locate this point outside.
  • Use a 4-inch hole saw to bore through the siding. Smooth any rough edges.
  • Attach a 12-inch connector duct to the wall cap with foil duct tape. From outside, slide the assembly through the hole. Seal with silicone and use stainless steel screws to fasten the cap to the siding. Fit a foam-rubber gasket if the wall cap doesn’t sit flush.
  • Back in the attic, pull the free end of the duct to the wall. Tape it securely to the wall cap’s duct connector.

A bathroom vent fan vent installed on an exterior brick wall, expelling air for proper bathroom ventilation and moisture control.

Make the Electrical Connections

  • Inside the bathroom, unscrew and gently remove the fan’s motor assembly. Set aside the screws in a safe place.
  • Unscrew the built-in receptacle or junction box cover from the fan housing. Join matching wires (white to white, black to black) using wire nuts. Attach the bare copper ground wire under the green grounding screw.
  • Replace the receptacle cover. Plug the motor back into the housing’s receptacle. Secure the motor with the original screws.

A person wiring a bathroom extractor fan inside a junction box, connecting power to the ventilator fan for bathroom.

Attach the Grille and Test

  • Fit the grille’s mounting wires into the slots on the fan housing. Push the grille until it sits snug against the ceiling.
  • Turn the breaker back on. Flip the fan switch to make sure everything runs smoothly.

Hands attaching the grille to a bathroom ventilation fan, securing the final step of the installation.

Extra Tips and Considerations for Installing an Extractor Vent

  • Most bathrooms need at least 50 CFM, while larger ones may require 80 CFM or more. The fan should be able to replace the air in the room within five minutes for effective moisture control.
  • Insulated ducts help prevent condensation buildup, which can lead to mold and water damage. If you have mould issues in your bathroom, read our comprehensive article about how to get rid of mould, with removal and prevention tips. 
  • Keep duct runs short and minimize sharp bends to maintain airflow. Every 90-degree turn reduces efficiency and lowers the fan’s CFM output. A straight path is always best.
  • A five-minute timer ensures the fan runs long enough to remove moisture but doesn’t stay on unnecessarily. This helps prevent mold, but also saves energy.
  • Fans with a sone rating of 1.0 or lower are very quiet. Higher ratings (above 3.0 sones) can be loud in small bathrooms.

Final Thoughts

Installing an extractor fan air vent is essential for keeping your bathroom fresh and free from moisture problems. A properly installed bath fan helps remove humid air, reducing the risk of mould and damage to walls and ceilings. To work effectively, the fan must vent to the outside, ensuring that excess moisture doesn’t linger indoors. If you have experience with home improvement projects and the right tools, you might be able to handle the installation yourself. However, since the process involves cutting through ceilings or walls and connecting electrical wiring, hiring a professional is the safest option.

At AV Modern Bathrooms, we offer complete bathroom renovations with professional installation. Our team works quickly, finishing most projects in just four days, and we always clean up at the end of each day. We also provide all the materials you need, so you don’t need to worry about choosing the right items. Our renovations start at £3,600, and every full renovation comes with a free LED mirror. Plus, we back our work with a 12-month workmanship warranty, and our maintenance team is always ready to assist if needed. If you’d like expert help with your bathroom renovation, book your free home visit today! You can also visit our showroom at 69-71 Higher Parr St, Saint Helens, WA9 1AD to see our range of products and discuss your desired project with our team.

• Call us at +44 1942 365989
• Email us at info@avmodernbathrooms.com

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Are you ready to transform your bathroom into a stunning, functional sanctuary? At AV Modern Bathroom, we specialize in creating beautiful, high-quality bathroom renovations tailored to your unique needs and style.