Extractor Fan CFM Calculator
Select Your Room Type
Required CFM
Replacing an extractor fan doesn’t have to be a nightmare. If your bathroom smells like a gym after a workout, or your kitchen windows fog up no matter how long you run the fan, it’s probably time for a new one. Most extractor fans you’ll find in homes built after 1990 are designed to be swapped out in under an hour-with no major renovations needed. But that doesn’t mean everyone can do it. Some setups are straightforward. Others? Not so much.
What Makes an Extractor Fan Easy to Replace?
The biggest factor is access. If your fan is mounted directly in the ceiling or wall with a clear path to the ducting and wiring, you’re in good shape. Most modern extractor fans use a simple mounting frame that clips into place. The old unit just pulls out, the new one slots in, and you reconnect the wires and duct. No drywall cutting, no framing changes, no special tools.But if your fan is buried behind tiles, plaster, or a false ceiling, or if the duct runs through a tight attic space, things get trickier. You’ll need more time, patience, and maybe a helper. Older homes (pre-2000) often have fans wired into circuits that weren’t meant for modern low-wattage units. That’s when you might need an electrician, not just a screwdriver.
What Tools Do You Actually Need?
You don’t need a full toolbox. Here’s what works:- Philips screwdriver (or a power drill with a Phillips bit)
- Wire strippers (or a sharp knife if you’re careful)
- Needle-nose pliers
- Flashlight
- Stud finder (optional, but helpful if you’re unsure where the joists are)
- Masking tape and a marker (to label wires)
No power saws. No drywall anchors. No cement. Just basic hand tools. If you’ve ever changed a light fixture, you’ve done 80% of the work already.
Step-by-Step: Replacing Your Extractor Fan
- Turn off the power. Go to your circuit breaker and shut off the circuit that powers the fan. Test it with a non-contact voltage tester. Don’t skip this. Even if the switch is off, the wires might still be live.
- Remove the cover. Most fans have a plastic or metal grille held by clips or screws. Pop it off or unscrew it. You’ll see the motor unit behind it.
- Disconnect the wiring. Take a photo of the wire connections before you touch anything. Use masking tape to label each wire: live (brown), neutral (blue), earth (green/yellow). Unscrew the wire nuts or terminal blocks and pull the wires apart.
- Remove the mounting frame. There are usually four screws holding the fan’s housing to the ceiling or wall. Unscrew them. The unit should drop down. If it’s stuck, gently wiggle it. Don’t yank the duct-those can crack easily.
- Check the duct. Look at the flexible duct connecting the fan to the outside. Is it crushed? Moldy? Kinked? If it’s in bad shape, replace it now. A new 100mm duct costs less than $20 and makes a huge difference in airflow.
- Install the new fan. Most replacement fans come with a mounting frame that matches standard cutouts (usually 150mm to 200mm). Slide the new unit into place, secure it with screws, and reconnect the duct. Make sure the arrow on the fan housing points toward the outside.
- Wire it up. Match your labeled wires to the new fan’s terminals. Twist them together with wire nuts and tuck them neatly into the box. Don’t let any bare copper stick out.
- Test it. Turn the power back on. Flip the switch. Listen for unusual noises. Check for airflow by holding a piece of tissue near the grille-it should pull it firmly.
When You Should Call a Professional
Not every job is DIY. Here’s when to stop and call someone:- Your fan is wired into a dedicated circuit with no easy access to the breaker panel.
- The duct runs through a cavity wall or roof space you can’t reach without removing cladding or ceiling panels.
- You’re replacing a fan in a bathroom with a heated floor or underfloor heating-those systems often share circuits and need careful load checks.
- You’re unsure about the wiring. If the wires are old, frayed, or colored differently (like red instead of brown), get an electrician. New Zealand’s electrical code is strict, and mistakes here can be dangerous.
- You live in a rental property. Landlords are legally responsible for repairs unless the tenant caused the damage. Don’t risk your bond.
Choosing the Right Replacement Fan
Not all extractor fans are created equal. Here’s what to look for:| Feature | What to Choose | Why It Matters |
|---|---|---|
| CFM (Cubic Feet per Minute) | At least 80 CFM for bathrooms, 150+ for kitchens | Too weak = moisture stays. Too strong = noise and wasted energy. |
| Noise Level | Below 1.0 sone for bathrooms, under 1.5 sone for kitchens | Anything above 2.0 sone sounds like a vacuum cleaner. |
| Timer or Humidity Sensor | Get one with a timer (5-15 min delay) | Keeps the fan running after you leave to clear lingering moisture. |
| Energy Rating | A or A+ (New Zealand Energy Rating Label) | Uses less electricity and lasts longer. Saves you money over time. |
| IP Rating | IPX4 or higher for bathrooms | Means it’s splash-proof. Essential near showers and sinks. |
Brands like Vent-Axia, Xpelair, and Manrose are common in New Zealand and widely available at Bunnings or local electrical suppliers. Avoid the cheapest no-name fans-they’re loud, inefficient, and often fail within a year.
Common Mistakes to Avoid
- Ignoring the duct. Replacing the fan but keeping the old, kinked duct is like putting a new engine in a car with a blocked exhaust. It won’t work right.
- Over-tightening screws. Plastic housings crack easily. Snug is enough.
- Not sealing gaps. Use silicone sealant around the edge of the housing where it meets the ceiling. Prevents air leaks and reduces noise.
- Forgetting the grille. Some new fans don’t come with a grille. You might need to buy one separately. Check before you install.
- Skipping the test. Always turn it on before you reattach the ceiling or wall panel. If it’s noisy or doesn’t spin, fix it now-not after you’ve put everything back.
How Long Does a New Extractor Fan Last?
A decent fan installed properly will last 8 to 12 years. Cheaper ones? Maybe 3 to 5. The motor is usually what dies first. If you hear grinding or buzzing, it’s not the bearings-it’s the windings. Time to replace it. Clean the grille every six months. Dust buildup reduces airflow and strains the motor.Many people don’t realize how much moisture affects their home. A poorly ventilated bathroom leads to mold on walls, peeling paint, and even rot in timber framing. A good extractor fan isn’t just about comfort-it’s about protecting your house.
Can I replace my extractor fan myself without any electrical experience?
Yes, if you’re comfortable turning off the power, labeling wires, and using basic tools. Most modern fans are designed for DIY. But if you’re unsure about any wiring, or if the circuit is shared with other appliances, call an electrician. Safety comes first.
How much does it cost to replace an extractor fan?
A basic fan costs between $50 and $120. Higher-end models with sensors or timers run $150-$250. If you do it yourself, that’s it. If you hire someone, labor adds $80-$150 depending on complexity. Most jobs take under two hours.
Do I need a permit to replace an extractor fan in New Zealand?
No, not for a like-for-like replacement. But if you’re changing the fan’s power rating, adding a new circuit, or modifying ducting that goes through external walls or roofs, you may need to notify your local council. Always check with your building consent authority if you’re unsure.
Why is my new extractor fan so noisy?
Most often, it’s because the duct is bent, crushed, or too long. A straight, short duct with minimal bends reduces noise dramatically. Also, make sure the fan is mounted securely-loose units vibrate and rattle. Check that the grille isn’t touching the fan blades.
Should I replace both the fan and the duct at the same time?
Yes, if the duct is older than 10 years, shows signs of mold, or is kinked. Even if it looks okay, old flexible ducts collect dust and moisture inside. Replacing both ensures your new fan works at full efficiency. It’s a small extra cost that pays off in performance and health.