Do you need a bathroom exhaust fan?

Bathroom exhaust fan: is it worth it?

Yes, for a bathroom with no window or one that stays damp long after a shower. Without a way out, steam from each shower lingers, and a bathroom that stays damp is one where mould can grow. Installing a fan involves choosing where it goes and having its power supply wired properly, both covered below. If your bathroom has a window you can keep open, you may manage without one.

These practical signs suggest a fan would help:

• Mould spots on the ceiling.
• A mirror that stays fogged long after your shower.
• A musty smell that comes back soon after cleaning.

Whether you call it an exhaust fan or a ventilation fan, HDB and condo bathrooms without a window are where it helps most. HDB's home care guide on walls advises allowing cross-ventilation in the flat, along with repainting walls regularly, to prevent problems.

The National Environment Agency (NEA) says in its ventilation guidance that occupants of homes can improve ventilation by opening doors and windows, and can use fans to promote air circulation when needed. A windowless bathroom has nothing to open, so a fan that sends damp air outside does that job instead.

A fan does not remove mould that is already there, so clean existing patches first. See how to remove bathroom mould.

Wall, window or ceiling fan

Which type suits you depends on what your bathroom already has.

Window or louvre fan. A window-mounted fan fits an existing louvre or window. It uses an opening you already have, so it is often the simplest option.

Ceiling fan. A ceiling-mounted fan needs a duct to carry damp air to the outside. Before any work starts, ask the installer to show you the route the duct will take and where it will vent.

Wall fan. A wall fan needs an opening through to the outside, so it takes the most planning. Settle the exact position with the contractor before anything is drilled.

Before any wall opening, check HDB's building works rules. Fixings have limits too: HDB's renovation guidelines for electrical works say power-driven nails and screws must not exceed 6mm in diameter and 40mm in penetration depth. Ask the installer how the fan and any trunking will be fixed.

Wiring and switches

Most of a toilet exhaust fan installation is electrical work. The Energy Market Authority (EMA) says in its guide to engaging Licensed Electrical Workers that installing or modifying wiring at home should be carried out or supervised by a Licensed Electrical Worker (LEW). EMA says electrical work in an HDB flat needs a Licensed Electrician, the class of LEW approved for loads of up to 45kVA. Check the LEW's licence card, which shows a photo, name and licence number, before work starts.

HDB's renovation guidelines for electrical works do not allow wiring, or wiring housed in metal or high impact PVC conduit, to be embedded in reinforced concrete slabs, beams, columns, walls, wall plaster or other finishes. Covering wiring with PVC trunking, or encasing surface wiring in metal or high impact PVC conduit, needs no HDB permit. SP Services Form CS/5H endorsed by HDB must be submitted for testing of new wiring. See HDB electrical renovation rules for more.

EMA's electrical safety advice adds that the LEW inspects and certifies the installation as safe before supply is turned on, and that new wiring, rewiring and extensions must also be tested by an authorised officer from SP Services Ltd first. It also says to keep electricity and water apart and not to touch switches or sockets with wet hands. Ask the LEW where the switch will go.

The cost depends on the job, so compare companies that offer electrical wiring and ask whether each quote covers the switch, trunking and testing. To see which jobs need a licence, read about work that needs an LEW.

Keeping it working

A fan only helps if it runs when the room is steamy and its grille stays clear. These practical habits keep it working well:

• Switch it on as you start your shower, and keep it running afterwards until the mirror clears.
• Clean the grille every few months. Switch the fan off first, only with dry hands and a dry switch, then wipe the dust away with a dry cloth or a vacuum brush.
• Do not open the fan housing or touch any wiring. If the fan stops working, leave it off and ask a Licensed Electrician to check it.

A fan will not fix a drain smell. It clears damp air, but a smell that rises from the drain needs a different fix. The guide to a bathroom drain smell explains what to check.

If mould keeps returning even with the fan in use, the mould FAQ answers common questions.

Questions