Fan Size Calculator
Ventilation fan is a device designed to provide a continuous supply of fresh outdoor air while exhausting stale indoor air. It works round‑the‑clock, often as part of a whole‑house ventilation strategy.
Extractor fan is a locally‑focused fan that pulls moisture, odors, or pollutants directly out of a specific room, such as a kitchen or bathroom. Unlike a ventilation fan, it usually runs only when you need it.
Why the confusion? Both move air, but they serve different goals
When homeowners hear "fan," the first image is a ceiling or table fan. The truth is that fans are engineered for very specific tasks. Understanding the purpose of each type helps you avoid over‑paying for the wrong unit or ending up with poor indoor air quality.
Core functional differences
- Purpose: A ventilation fan delivers continuous fresh air exchange to improve overall indoor air quality (IAQ). An extractor fan targets a localized source of humidity or odor and expels it directly outside.
- Operation schedule: Ventilation fans typically run continuously or on a timed schedule (e.g., 15minutes every hour). Extractor fans fire on demand - when you turn them on or when a humidity sensor trips.
- Placement: Ventilation fans are often installed in ducts, rooftops, or wall vents that serve whole‑house or zone ventilation. Extractor fans sit in the ceiling of a bathroom, above a kitchen range, or in a laundry room.
Performance metrics you need to compare
Both fan types are rated by the same basic measures, but the way you interpret them changes with the application.
| Metric | Ventilation Fan | Extractor Fan |
|---|---|---|
| Typical airflow (CFM) | 100-400CFM per unit | 50-150CFM per unit |
| Static pressure tolerance | Low to moderate (0.2-0.5 in‑wg) | Higher (0.5-1.0 in‑wg) for ducted lengths |
| Noise level (dB) | 20-35dB(A) - often quieter because of larger blades | 30-45dB(A) - may be louder due to higher speed |
| Control options | Timers, humidistats, HRV/ERV integration | Wall switches, humidity sensors, auto‑off |
| Energy use (W) | 30-80W (continuous) | 15-35W (intermittent) |
Notice the CFM rating-cubic feet per minute-shows how much air moves. A whole‑house ventilation fan needs a higher CFM to replace the total volume of indoor air, while an extractor only needs enough to clear the specific room’s moisture load.
How static pressure affects installation
Static pressure measures the resistance a fan must overcome. Long duct runs, elbows, or insulated ducts increase pressure. Ventilation fans usually sit close to the outdoor intake, so they face lower pressure. Extractor fans often sit at the end of a short vent hose that must push air up through a roof or wall, which can raise static pressure. Choosing a fan with the right tolerance avoids excessive noise and reduced performance.
Noise considerations for a comfortable home
Noise is expressed in decibels (dB). A typical bedroom can tolerate up to 30dB without disturbance. Ventilation fans, because they're larger and slower, tend to stay below this threshold. Extractor fans, especially cheaper models, can climb above 40dB when pulling strong drafts. Look for fans with acoustic enclosures or variable‑speed motors if quiet operation matters.
Energy efficiency and building codes
Many regions have minimum ventilation requirements for new construction. For example, the New Zealand Building Code mandates a minimum of 0.35 air changes per hour for residential dwellings, unless a certified heat recovery system is installed. Selecting a fan with the appropriate energy rating can keep you compliant while saving electricity.
Heat recovery ventilators (HRVs) and energy recovery ventilators (ERVs) pair with ventilation fans to reclaim heat from exhausted air. This reduces the heating load in winter and cooling load in summer. An HRV is ideal for cold climates; an ERV works better where humidity control is also a priority.
Choosing the right fan for your situation
- Identify the goal. Need whole‑house fresh air? Go ventilation. Need to banish steam from the shower? Choose extractor.
- Calculate required CFM. Use the formula: CFM = (Room volume × Desired air changes per hour) ÷ 60. For bathrooms, a common rule is 1CFM per square foot of floor area plus an extra 50CFM for shower enclosures.
- Check static pressure limits. Measure duct length and count elbows; use fan curves from manufacturers to ensure the fan can overcome the total pressure.
- Set noise expectations. If the fan will be in a bedroom or open‑plan living area, aim for ≤30dB. Look for fans with insulated housings.
- Factor in energy usage. Continuous fans should have EC or DC motors for better efficiency. Extractor fans benefit from humidity‑triggered auto‑off to prevent wasted kilowatts.
- Verify compliance. Confirm the unit meets local building code references-often listed as “AS/NZS 1668.2” for ventilation in NewZealand.
Following these steps prevents you from buying a bathroom fan that can’t handle your kitchen’s grease‑laden exhaust or a ventilation unit that’s oversized, noisy, and wasteful.
Related concepts to explore
Understanding how fans fit into a broader ventilation strategy helps you future‑proof your home.
- Inline fan - installed within the ductwork for quiet, balanced flow.
- Makeup air unit - supplies the fresh air that exhausted air displaces, essential for tightly sealed homes.
- Humidity sensor - automates extractor fan operation, reducing energy waste.
- Air quality monitor - measures CO₂, VOCs, and particulate matter, informing ventilation needs.
Each of these devices can be combined with either a ventilation or extractor fan to create a smarter, healthier indoor environment.
Troubleshooting common issues
- Fan won’t start. Check power supply, reset circuit breaker, and verify the motor capacitor (for AC motors).
- Poor airflow. Inspect duct for blockages, clean the fan blades, and confirm static pressure isn’t exceeding the fan’s rating.
- Excessive noise. Tighten mounting screws, replace worn bearings, or add an acoustic liner to the duct.
- Moisture still builds up. Ensure the extractor fan’s capacity matches the room’s moisture load; consider adding a secondary fan or upgrading to a higher‑CFM model.
Regular maintenance-cleaning filters, checking for rattles, and confirming sensor calibration-keeps both fan types operating at peak efficiency.
Bottom line
If you’re after a ventilation fan vs extractor fan decision, remember: ventilation fans handle whole‑house air renewal, run continuously, and are designed for low noise and energy efficiency. Extractor fans are spot‑cleaners, fire on demand, and need higher static pressure handling. Match the fan’s purpose, CFM, pressure tolerance, and noise level to your specific room and code requirements, and you’ll end up with fresh, dry air without wasting power.
Frequently Asked Questions
Do I need both a ventilation fan and an extractor fan?
Many homes benefit from both. A ventilation fan keeps overall indoor air fresh, while an extractor fan tackles high‑moisture areas like bathrooms and kitchens. Using both ensures optimal IAQ and prevents mold.
Can I replace my bathroom extractor with a ventilation fan?
It’s not recommended. A ventilation fan provides lower airflow and is meant for continuous operation, which won’t clear bathroom steam fast enough. You’ll likely notice lingering humidity and a higher risk of mold.
What CFM rating is enough for a medium‑size kitchen?
A rule of thumb is 100CFM for every 10sqft of cooking surface, plus an extra 50CFM for a deep fryer or grill. Most medium kitchens (250‑300sqft) do well with 300‑400CFM extractor fans.
How often should I clean my ventilation fan?
At least once a year, or more often if you live in a dusty area. Turn off power, remove the grille, vacuum the blades, and wipe the housing with a damp cloth. Clean filters if present.
Are there any grants for installing energy‑recovery ventilators?
NewZealand’s Home Energy Upgrade scheme occasionally offers rebates for certified HRV or ERV installations. Check the latest government website or local council announcements for eligibility and application deadlines.