Updated for 2026 — Written by the Home Genie team, Singapore’s home appliance specialists with over 40 years of industry experience.
Singapore’s humidity averages 80–90% year-round. After a hot shower, your bathroom becomes a breeding ground for mould, mildew, and bacteria — unless you remove that moisture quickly. A properly sized exhaust fan is the single most effective solution, yet it’s one of the most neglected appliances in Singapore homes. Let’s fix that.
Why Your Bathroom Needs an Exhaust Fan
Every shower generates a significant amount of moisture. In a typical HDB bathroom with no window (or a window that faces another flat’s corridor), that moisture has nowhere to go. The result:
- Mould on ceiling and grout lines — The black spots that keep coming back no matter how much bleach you use
- Peeling paint and bubbling plaster — Trapped moisture damages wall finishes over time
- Musty odour — That permanent damp smell in windowless bathrooms
- Health risks — Mould spores trigger allergies, asthma, and respiratory issues
An exhaust fan removes humid air from the bathroom and pushes it out through a duct to the outside of the building. It’s the difference between a bathroom that stays clean and one that needs constant scrubbing.
Types of Bathroom Exhaust Fans
| Type | How It Works | Best For | Price Range |
|---|---|---|---|
| Ceiling-mounted | Installed in the ceiling with ducting to the external wall or roof | False ceilings, renovated bathrooms | $60–$200 |
| Wall-mounted | Fitted directly into an external wall opening | Bathrooms with an external wall | $40–$150 |
| Window-mounted | Installed in a window opening (glass or louvre) | Bathrooms with windows — common in older HDB | $40–$120 |
| Inline duct fan | Installed within the ducting, not visible in the bathroom | Long duct runs, multiple extraction points | $80–$250 |
For most HDB bathrooms, a ceiling-mounted or wall-mounted fan is the standard choice. The type depends on your bathroom layout and whether you have direct access to an external wall.
How to Size an Exhaust Fan
Exhaust fans are rated in CFM (Cubic Feet per Minute) or m³/h (cubic metres per hour). The right size depends on your bathroom volume. Here’s the simple formula:
Required CFM = Bathroom volume (cubic feet) × 8 air changes per hour ÷ 60
For typical HDB bathrooms:
| Bathroom Size | Volume (approx.) | Minimum CFM | Recommended Model |
|---|---|---|---|
| Small toilet (25–35 sq ft) | 200–280 cu ft | 25–40 CFM | KDK 15TGQ (6") |
| Standard HDB bathroom (35–50 sq ft) | 280–400 cu ft | 40–55 CFM | KDK 20TGQ (8") |
| Master bathroom (50–70 sq ft) | 400–560 cu ft | 55–75 CFM | KDK 25TGQ (10") |
| Large condo bathroom (70+ sq ft) | 560+ cu ft | 75+ CFM | KDK 30RHF or equivalent |
Our rule of thumb: For standard HDB bathrooms, an 8" (20cm) exhaust fan is the safe default. It handles the typical bathroom size with some headroom. Going one size up is always better than going too small.
Our Top Exhaust Fan Picks for Bathrooms
1. KDK 15TGQ / 20TGQ — Most Reliable
The KDK TGQ series is the workhorse of Singapore bathrooms. Glass-panel front for easy cleaning, quiet operation, and the KDK reputation for motors that last 10+ years without issues. Available in 6", 8", and 10" sizes. This is what we install in our own homes.
Price: $60–$120 | Noise: Very quiet | Best for: Any HDB bathroom
2. KDK 24CDQN — Premium Ceiling Mount
For false-ceiling installations, this duct-type exhaust fan connects to a 100mm duct and exhausts air silently through the ceiling void to the outside. Near-silent operation makes it ideal for master bathrooms adjacent to bedrooms.
Price: $100–$160 | Noise: Near-silent | Best for: False ceiling bathrooms, master bathrooms
3. KDK 15EGKA — Budget Window Mount
If your bathroom has a window and you need a straightforward solution, this window-mount exhaust fan does the job reliably. Auto-shutters prevent insects from entering when the fan is off.
Price: $50–$80 | Noise: Moderate | Best for: Older HDB with bathroom windows
Noise Levels: What to Expect
Exhaust fan noise is measured in sones or dB(A). Here’s a practical reference:
| Noise Level | Sound Comparison | Acceptable For |
|---|---|---|
| Under 1.0 sone (under 30 dB) | Barely audible — like leaves rustling | Master bathrooms, night use |
| 1.0–2.0 sones (30–40 dB) | Background hum — like a refrigerator | All bathrooms |
| 2.0–3.0 sones (40–50 dB) | Noticeable — like a conversation | Guest bathrooms, kitchens |
| Over 3.0 sones (50+ dB) | Loud — intrusive | Avoid for residential use |
KDK fans generally operate in the 1.0–2.0 sone range, which is quiet enough for any residential bathroom. Cheaper unbranded fans often run at 3.0+ sones — the noise is noticeable and can be annoying during night showers.
Installation Considerations for HDB
Wall-mounted installation: Requires a hole through the external wall (typically 150mm or 200mm diameter). In HDB flats, you can core a hole through the bathroom wall that faces the common corridor or air well. HDB regulations require the opening to have proper weatherproofing.
Ceiling-mounted installation: The fan mounts in the false ceiling, and a flexible duct runs from the fan to an external vent. The duct should be as short and straight as possible — every bend reduces airflow efficiency. Maximum recommended duct length is 3–4 metres.
Key rules:
- The exhaust must vent to the outside, not into the ceiling void or another room
- Use proper ducting material — rigid or semi-rigid aluminium, not the cheap PVC flex hose that sags and traps moisture
- Install a backdraft damper (most KDK fans include one) to prevent outside air from flowing back in
- Electrical work must be done by a licensed electrician
Should You Connect the Fan to the Light Switch?
Many installations wire the exhaust fan to the bathroom light switch so it runs whenever the light is on. This works, but a better approach is a separate switch with a timer delay. The fan continues running for 10–15 minutes after you turn it off, removing the remaining humidity after your shower. This costs only slightly more to install and is significantly more effective at preventing mould.
Common Mistakes to Avoid
- Undersizing the fan — A 6" fan in a standard bathroom moves air too slowly. When in doubt, go one size up.
- Venting into the ceiling void — The moisture must go outside. Venting into the ceiling causes mould growth above the false ceiling where you can’t see it.
- Using cheap flex ducting — It sags, traps moisture, and reduces airflow. Use rigid or semi-rigid aluminium ducting.
- Never running the fan — Some homeowners install a fan and then never use it because of the noise. Buy a quiet model (under 2 sones) and actually use it.
- No backdraft damper — Without a damper, outside air (including insects and smells from other units) enters your bathroom when the fan is off.
Browse our full range of exhaust and ventilating fans at Home Genie. We offer free installation advice and can recommend the right fan for your specific bathroom setup. Visit us at 61 Kaki Bukit Avenue 1, #04-23 or WhatsApp +65 8837 6682.
Frequently Asked Questions
What size exhaust fan do I need for my HDB bathroom?
For a standard HDB bathroom of 4–6 sqm, a ventilation fan with an airflow rating of 150–200 CFM (cubic feet per minute) is recommended. The general rule is 1 CFM per 0.09 sqm of floor area, but for bathrooms it is better to oversize slightly to account for moisture from hot showers. Popular choices include 6-inch (150mm) and 8-inch (200mm) exhaust fans.
How loud are bathroom exhaust fans?
Bathroom exhaust fan noise is measured in sones. A quiet fan operates at 0.5–1.5 sones, which is barely noticeable. Standard fans typically run at 2–4 sones, which is comparable to normal conversation. For bedrooms with attached bathrooms, choose a fan rated 1.0 sone or below to avoid disturbing sleep. KDK ventilation fans are known for their quiet operation.
Should I leave my bathroom exhaust fan running after a shower?
Yes, you should run the exhaust fan for at least 15–20 minutes after showering to fully remove moisture from the bathroom. This prevents mould and mildew growth, which is especially important in Singapore’s humid climate. Some exhaust fans come with a built-in timer or humidity sensor that automatically turns off the fan when moisture levels return to normal.
Can I install a bathroom exhaust fan in an HDB flat without a window?
Yes, HDB flats typically have a ventilation shaft or duct system specifically designed for windowless bathrooms. Your exhaust fan connects to this existing duct to expel moist air outside. Make sure the fan is compatible with your duct size (usually 100mm or 150mm). Installation should be done by a qualified electrician to ensure proper connection and sealing.
How often should I clean my bathroom exhaust fan?
Clean your bathroom exhaust fan every 3–6 months for optimal performance. Dust and grime buildup on the blades and grille can reduce airflow by up to 50%. Turn off the power, remove the cover, and wipe the blades with a damp cloth. In Singapore’s dusty environment, more frequent cleaning may be needed. Replace the fan if cleaning no longer restores proper airflow.
