how to fit an extractor fan

How to Fit an Extractor Fan

When it comes to bathroom ventilation, cracking open a window simply is not enough, you need an extractor fan.

But what are they and how do they work? More importantly, how do you install an extractor fan? Plumbworld has put together this guide to help you understand how to fit a fan to both your wall or ceiling in a bathroom to improve ventilation.

We will also discuss why you may need an extractor fan - not just for removing steam or smells - in your bathroom. We’ll guide you through, step-by-step, for the installation process and answer the key questions about fitting an extractor fan.

Read on to find out more about extractor fans and how to fit them into your bathroom…

What are extractor fans?

what are extractor fans?

Essentially, an extractor fan removes moisture from your bathroom and is essential if you want to keep your bathroom looking fresh.

Why do you need an extractor fan?

By helping remove moisture from the air, a bathroom exhaust fan prevents mould from forming in your bathroom. Mould and mildew thrive in warm, damp environments such as behind your toilet, basin, bathroom furniture or tiles, so it’s vital to keep your bathroom well ventilated.

Read more: How to Remove Bathroom Mould

Using an extractor fan during or after a shower or bath, depending on your home’s airflow, will help to remove moisture from the air. Even when the fan is on, you should remember to keep the door open when your bathroom isn’t in use and open a window to keep it ventilated.

What are the rules on bathroom ventilation?

UK regulations regarding how much ventilation your bathroom needs are outlined in the Building Regulations Document F. It is a lengthy document, so we have picked out the essential information below.

  • A UK bathroom must be ventilated by either a window or an extractor fan.
  • If your bathroom has a toilet only, you are fine to use a window alone as your source of ventilation.
  • In new-build bathrooms with a bath and shower, mechanical ventilation is required in the form of an extractor fan. This is because new-builds are built to be more airtight, so natural ventilation is much lower.
  • The ventilation requirements for a bathroom are 15 litres per second/ 54m3 per hour

The last point means that the 15l/s, or 54m3/hr, refers to the measurement of how much old air is replaced by new air.

What are the types of extractor fans?

what are the types of extractor fans?

When it comes to the types of extractor fan, there are three common setups, which are detailed below:

  • Ceiling fan, ducting through roof eaves, out an external wall vent
  • Wall fan, ducting straight through to external vent
  • A fan in a glass window

Out of the three setups, the first two are the most common and easiest to install. Crucially, there are specific names for these setups. A ceiling fan is called ‘inline’ or a ‘centrifugal fan’. They operate differently, however. A wall fan will be called an ‘axial’ fan and we’ve explained each one more below.

  • Axial fans: these connect directly through an external wall and are used when the air doesn't need to be moved long distances. 
  • Centrifugal fans: often fitted in the ceiling, these are designed for bathrooms that are not close to an external wall, but over 1.5m away.
  • Inline fans: these are usually fitted in the ceiling and can be used for extra-long ducting distances of up to 40 metres.

What size extractor fan do I need?

To know the size of the bathroom extractor fan you need, you will need to calculate the extraction rate - the figure that tells you how much air can be removed from a room in one hour. This is measured in metres cubed per hour.

To work out the extraction rate, you need to calculate the cubic metres of your bathroom. With a measuring tape, note down the height, width and length of the room in metres. Once you have done this, multiply the three figures together to get the size in cubic metres.

Read more: Everything You Need to Know About Bathroom Ventilation

The extraction rate you need for your bathroom will depend on its size. However, as we’ve said, building regulations say that the minimum fan extraction rate your bathroom should have is 54 m^3/hr (or 15 l/s) if the room doesn’t have an openable window. So, make sure you at least meet this level.

Tip: to work out the litres per second, l/s, divide your cubic metres figure by 3.6. This is because one l/s is around 3.6m^3/hr - cubic metres per hour.

How much do extractor fans cost?

The average cost of an extractor fan depends on whether it is new or a replacement. You may then also need to consider the cost of installation. The average cost for replacing an existing fan is £175 for the fan and installation. However, for a new fan, it can cost around £300.

How to fit a ceiling extractor fan

What you will need

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

The Process

1.Plan: Make sure there is enough room in the loft for the fan. If you are making a hole in your ceiling, always cut between the horizontal supporting beams. Also, use an electronic detector to check for any hidden wiring or piping.

2. Create a hole in the ceiling: For a new extractor fan in a new place, choose the location where you want to install your fan and clear away insulation.

3. Use your pencil to mark the position of the vent part of the fan on the ceiling. Drill a hole through the ceiling on a point on your outline. Then, using a pad saw, cut around the outline to create a hole and carefully remove waste material.

4. Fit the vent onto the ceiling: Attach the fittings onto the vent that will secure to the duct pipe in your loft. Once in place, hold the vent over the space and mark the location of the holes where it will be secured to the ceiling.

5. Drill holes where you have marked and insert the fittings, such as wall plugs. Hold the vent in place and secure it using your screwdriver. Remember, depending on your ceiling, the correct fixings may vary.

6. Install the fan in the loft: Depending on the design, the fan should be secured horizontally to the floor or the loft side of the ceiling. Use your pencil to mark where the frame of the fan will be attached and then drill holes. Insert the fittings where necessary, and secure the frame with your screwdriver.

7. Attach the ducting: Secure the flexible ducting to the ceiling vent and onto one side of the extractor fan. On the other side of the fan, secure ducting that attaches to the exterior source of ventilation.

8. Make the electrical connections: All electrical work must be carried out by a qualified electrician. Depending on the fan, it can be operated by a separate control or connected to the light switch. Once this is done, fit the grill cover onto the bathroom ceiling, over the vent. 

9. When you are confident with the extractor fan, replace the insulation in the loft.

How to fit a wall-mounted extractor fan

What you will need

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

The Process

1.Plan for your fan: Use a pipe and cable detector to check for any hidden pipes and cables. Make sure there are no pipes on your outside wall that will block the fan. Also, make sure that the outlet isn't directly below a window.

2. Create the hole: For fitting a fan in a new place, you will need to make a hole in your wall. Once you have made sure the wall is clear, hold your fan in place and use your pencil to trace around the circular edge of the fan. Mark the centre point on the wall and drill a hole through the wall for reference.

3. Then, drill a series of holes around the circular tracing of your fan at around 35mm apart. Once you have done this, use a chisel and hammer to ‘chop out’ the wall within.

4. Insert the ducting: Once you have created the hole, insert the flexible ducting. It should fit at a slightly downward angle and be flush against the internal and external wall. You can trim it if you need to with your saw.

Tip: If you need to repair any plasterwork on the inside or external wall around where you have drilled, this is the time to do so.

5. Fit the fan: On the inside wall, fit the fan over the hole and use your pencil to mark where it is secured to the wall. Drill the holes to insert any necessary fittings. Position the fan over these holes and secure it in place using your screwdriver.

6. Do the same for the outside wall.

7. Make the electrical connections: Like for the ceiling fan, a qualified electrician must make the appropriate connections. Again, depending on the type, the fan can be operated by a separate control or by the light switch.

8. Once this has been done, secure the grill covers over the fan on the inside the bathroom and on the outside wall. If the cover has a slatted design, make sure to position them horizontally to keep the rain out.

There's more to installing a shower than the shower itself and the enclosure, the shower tray. But how do you fit a shower tray? Plumbworld is here to help.

For more information on bathroom ventilation, take a look at the following posts - Everything You Need to Know About Bathroom Ventilation - Tackling condensation in the home.

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