Bathroom always damp? A guide to exhaust fans for HDB & condo homes

A lot of Singapore bathrooms — especially internal HDB ones with no window — just can't dry out on their own. The result is familiar: black mould creeping across the ceiling, a musty smell that never quite leaves, paint bubbling near the shower, and towels that stay damp for days. The fix is almost always the same: proper extraction.

An exhaust (ventilating) fan pulls the warm, moist air out of the room and vents it outside, so the bathroom dries in minutes instead of hours. Here's how to choose one.

Why it's worth doing

• Stops mould before it starts. Mould needs moisture; clear the moisture and it has nothing to grow on.
• Protects your paint and grout. Constant damp lifts paint and degrades silicone and grout lines.
• Kills the smell. Extraction removes odours and stale air, not just covers them.
• Better for health. Less mould and damp means cleaner air, which matters if anyone in the home has allergies or asthma — the same reason regular aircon chemical washing is worth keeping up with.

The three types — and when to use each

Window-mount

Fits into a window pane or a vent opening. The simplest option when the bathroom has a window or an external wall opening already. Often cord-operated or with an electric shutter, and weather-resistant so rain doesn't blow in.

Wall-mount

Mounts on an external wall and vents straight through it. Models with an automatic shutter open when running and close when off, which blocks draughts, insects and backdraft. A good choice when there's an outside-facing wall but no usable window.

Ceiling-mount (ducted)

Sits flush in the ceiling and ducts the air out through the false ceiling to a riser or external vent. This is the tidiest, quietest option and the one most internal HDB bathrooms need — the air has to be carried out, since there's no external wall to vent through directly. The quiet "sirocco" ceiling units are barely audible at 20–35 dB(A) — a different beast from the bigger ceiling fans you'd pick for living spaces.

You can compare all three styles in our ventilation-fan range — each listing shows the mount type, air volume and noise level.

How to size it

An exhaust fan is rated by air volume — how much air it moves per hour, in m³/h. Bathrooms want roughly 10–15 air changes per hour. The quick method:

• Work out the room volume: length × width × height (in metres).
• Multiply by 15 to get the air volume you want, in m³/h.
• Pick a fan rated at or above that figure.

Example: a typical HDB bathroom of 2m × 1.5m × 2.6m is about 7.8m³. ×15 ≈ 120 m³/h. A small ceiling or wall unit (often rated 85–200 m³/h) comfortably covers it.

Bigger or shared bathrooms, or ones with a bathtub, push the number up — size up rather than down, since an undersized fan just runs constantly and never wins.

Features worth having

• Automatic shutter / backdraft flap: stops outside air, insects and smells coming back in when the fan's off.
• DC motor: quieter and lower power for a fan that may run for long stretches.
• Timer or motion sensor: runs on after you leave (or switches itself on when you enter) so the room fully clears — great for the forgetful.
• Low noise rating: look for the dB(A) figure on the spec; the quiet ceiling units sit around 20–35 dB(A).

Installation: it's a wired job

An exhaust fan needs an opening (window, wall or ceiling cut-out), ducting where the air has to be carried out, and a proper wired connection — it's not a plug-in appliance. In Singapore that wiring should be done by a licensed electrical worker; SparkFlow is EMA-registered (ME05 L1), so the fit is by-the-book for HDB and condo. Where the job calls for a fresh point off the wall, we can run a dedicated switch or fused connection at the same time. We handle the cut-out, the duct run and the wiring as one job.

Common mistakes

• Buying too small. A fan rated below the room's air-change need runs non-stop and still leaves the room damp.
• No ducting on an internal bathroom. A ceiling fan that just pushes air into the false ceiling moves the damp problem upstairs — it has to vent outside.
• No backdraft shutter. Without one, smells and insects drift back in when the fan's off.
• Running it for 30 seconds. Leave it on for 10–15 minutes after a shower (or fit a timer) so the moisture actually clears.

The takeaway

If your bathroom won't dry out, the answer is a correctly-sized exhaust fan vented to the outside — ceiling-mount for internal HDB bathrooms, wall or window-mount where there's an external opening. If you're already planning a bathroom renovation, fold the fan into that scope so the ducting and false ceiling are done in one go. Send us your bathroom size and a photo of the ceiling or wall and we'll recommend the right unit and install it properly. Start by browsing the ventilation-fan range.