How to Choose a Bathroom Exhaust Fan

Choosing the right bathroom exhaust fan is important for maintaining air quality and preventing moisture damage in your bathroom. With several types and sizes available, selecting the best model for your needs can be a challenge. This guide provides tips on the key factors to consider when shopping for a bathroom exhaust fan.

Determine the CFM and Sones You Need

CFM (cubic feet per minute) indicates the airflow volume capacity of the fan. You need adequate CFM for the size of your bathroom to effectively remove humidity and odors. As a general guideline:

  • Small bathrooms (up to 50 sq. ft.) need at least 50 CFM
  • Medium bathrooms (50-100 sq. ft.) need 70-80 CFM
  • Large bathrooms (100+ sq. ft.) need 100+ CFM

Sones rate the loudness of the fan. Look for models with ratings of 1.0-2.0 sones or less for quiet operation.

Measure your bathroom size and identify key moisture sources (shower, tub, multiple sinks, etc.) to determine the right CFM. Also factor in the fan’s sone rating when choosing models. Getting the highest CFM and lowest sones within your budget ensures the best performance.

Consider Fan Types

There are two main types of bathroom exhaust fans:

Ceiling Fans

Ceiling fans are installed in the ceiling and vent air through a duct leading outside. Key features:

  • Provide the strongest airflow and moisture removal.
  • Allow flexible venting through ceilings or walls.
  • Fan/motor is hidden for a flush, seamless look.

If you’re remodeling or building a bathroom, ceiling models are often the best choice.

Wall Fans

As the name implies, wall fans mount on the wall and vent air directly outdoors through the wall or soffit. Benefits include:

  • Easier DIY installation than ceiling fans.
  • Often less expensive than ceiling units.
  • Fit well in half-baths or small spaces.

The main drawback is that wall units push air a shorter distance than ceiling fans and may provide less efficient air circulation.

Evaluate your bathroom layout, budget, and needs to decide between a ceiling or wall exhaust fan.

Choose the Right Size

In addition to CFM, the physical size of the fan must suit your space. Bathroom fans come in a range of standard housing sizes:

  • 4-inch fans for compact baths
  • 5-inch or 6-inch fans for medium baths
  • Larger 7-inch, 8-inch or 10-inch fans for big bathrooms

Measure the existing venting space (for replacement) or plan the ducting path (for new installs) to pick an appropriately sized fan. It should fit the ceiling or wall space with room for proper airflow and venting.

An undersized fan won’t clear moisture well. But an oversized unit wastes energy and money. Match the right capacity CFM fan to the right housing size for optimal performance.

Consider Special Features

Many bathroom fans now offer extra features that enhance function or convenience:

  • Humidity sensors automatically switch the fan on when moisture levels rise. This provides hands-free, added moisture protection.
  • Motion sensors turn on the fan when someone enters the bathroom. They ensure the fan runs when needed but conserves energy when the room is unused.
  • Delayed shut-off timers (2-60 minute range) let the fan run for a set time after you leave to fully clear humidity.
  • Night lights provide soft illumination without turning on bright overhead lights at night.
  • Heater coils warm the air to avoid cold drafts and reduce condensation.
  • Bluetooth speakers let you play music through the fan.

Think about which special add-ons would enhance your bathroom experience and look for models offering the features you want.

Verify Electrical Requirements

Before purchasing, check your bathroom’s electrical setup to ensure compatibility with the new fan:

  • Voltage – 120V is standard for bathroom fans. Match the voltage to your home’s electrical system.
  • Amperage – Fans draw anywhere from about 1 amp to over 5 amps. Your circuit must support the amps required.
  • Ducting – Factor in the CFM rating and ducting length to size the wiring appropriately. More airflow and longer duct runs need bigger amperage capacity.

Consult the manufacturer specs and your electrician if unsure about electrical requirements. Planning ahead prevents issues down the road.

Choose an Efficient, Quiet Motor

The motor powers the fan’s operation. Brushless DC motors are the most energy-efficient choice. They move air quietly and provide years of reliable performance.

Many fans now have DC ECM motors that offer similar benefits. Stay away from outdated shaded pole or PSC motors – they waste energy and don’t last as long.

Look at the sones rating to confirm the fan operates quietly. Well-made DC or ECM motors position bathroom fans as an upgrade rather than a nuisance.

Select a Durable Housing Material

Housings for bathroom fans come in several material options:

  • Plastic – Typically the most affordable choice but prone to rattling.
  • Steel – Provides better durability than plastic and dampens vibration.
  • Cast aluminum – Offers the most rugged housing construction. Cast aluminum resists moisture corrosion and attenuates sound well.

Pricier metals like cast aluminum or steel make sense for busy family baths or humid, steamy spaces. Any material properly installed works fine for low to moderate usage.

Check the Warranty Coverage

Given the hot, wet and humid bathroom environment, look for robust warranty protection:

  • Motor – 5-year to limited lifetime coverage.
  • Parts – At least 2 to 3 years, preferably 5 years.
  • Labor – 1 year minimum workmanship warranty.

Extensive warranty periods demonstrate the manufacturer’s faith in the fan’s quality. It also protects your investment if defects arise.

How to Choose a Bathroom Exhaust Fan: Key Takeaways

  • Size the CFM to match or exceed the bathroom’s square footage. Also get the quietest sones rating you can afford.
  • Ceiling fans provide the strongest airflow but wall units work well in smaller baths.
  • Verify the fan’s physical dimensions properly fit your space.
  • Consider special features like humidity sensors, motion activation, and delayed shut-off for added value.
  • Check electrical requirements and motor efficiency when comparing models.
  • Durable metals like aluminum better resist moisture issues versus plastic housings.
  • Extended warranties give you peace of mind. Aim for at least 2-5 years of coverage.

Choosing the optimal bathroom exhaust fan takes some planning. Assessing your bathroom’s needs, finding models that best fit them, and verifying specifications lead to the right purchase decision. Investing in a quality fan improves comfort and air quality while protecting your bathroom from moisture damage.

Types of Bathroom Exhaust Fans

There are two main classifications of bathroom exhaust fans to choose from:

Ceiling Mounted Bathroom Exhaust Fans

Ceiling mounted fans are installed in the ceiling and vent outward through ductwork. Benefits include:

  • Provide the maximum airflow to remove humidity, odors, and other contaminants.
  • Allow flexible venting through ceilings or walls.
  • Fan/motor assembly hidden from view maintains a clean look.
  • Most effective solution for renovated or new bathrooms.

Ceiling fans come in a range of CFM capacities and sizes. Choose a model with ample CFM abilities for your bathroom’s square footage. Measure the existing ductwork space or plan the needed duct run when picking the right physical size.

Key Components of Ceiling Fans

  • Housing – Made of plastic, steel or cast aluminum. Holds motor and blades.
  • Motor – Powers the fan’s operation. DC motors offer optimal efficiency and quiet performance.
  • Blades – Designed for optimal airflow. Metal or plastic construction.
  • Grill – Covers and protects fan blades. Usually matching housing material.
  • Damper – Flaps or dampers prevent backdrafts.

Some advantages of ceiling mounted bathroom exhaust fans:

  • Strongest airflow and suction to remove humidity and odors.
  • Flexible venting options (ceilings or walls) to optimize installation.
  • Hidden, integrated look maintains aesthetic appeal.
  • Ideal for renovated or new bathrooms.
  • Wide range of sizes match any space.

Ceiling models are the most capable bathroom ventilation solution in most cases.

Wall Mounted Bathroom Exhaust Fans

Wall mounted bathroom exhaust fans are installed directly on an interior bathroom wall or soffit on an exterior wall. Benefits of wall fans include:

  • Typically easier DIY installation than ceiling fans.
  • Often a more budget-friendly option.
  • Well suited for small bathrooms and half-baths.

The main limitations are weaker airflow than ceiling fans and less venting flexibility. But wall units work well for modest ventilation needs in compact bathrooms.

Components of Wall Mounted Bathroom Exhaust Fans

While simpler than ceiling fans, wall mount bathroom exhaust fans consist of:

  • Housing – Made of plastic or metal to enclose fan.
  • Motor – Provides airflow. DC motors are most efficient.
  • Blades & Grill – Facilitate airflow while protecting blades.
  • Damper – Allow one-way air movement out while closing off backdrafts.
  • Duct adapter – Connects fan unit to duct leading outdoors.

Key advantages of wall mounted bathroom exhaust fans:

  • Typically easier to install than ceiling fans.
  • Offer a budget-friendly bathroom ventilation option.
  • Well suited for small baths and half-baths.
  • Require shorter duct runs than ceiling fans.

While airflow is less than a ceiling fan, wall units work well for smaller bathrooms.

Bathroom Exhaust Fan Types: Key Considerations

  • Ceiling fans offer stronger ventilation while wall units suit smaller baths.
  • Most ceiling fans use 4″-8″ ducting while wall fans use 3″-4″ ducting.
  • DC motors provide the best efficiency and quietest operation.
  • For renovated/new baths, ceiling fans allow optimal placement. Wall fans work well for upgrades.
  • Carefully match CFM abilities and physical size to bathroom requirements.

Evaluate bathroom layout, space constraints, venting needs and budget when choosing the best fan type.

Bathroom Fan Sizing Guide

Selecting a bathroom fan with adequate CFM airflow abilities prevents moisture issues. But the physical size must also fit your space. Use this guide to pick the properly sized fan:

Measure Bathroom Square Footage

The bathroom’s size mainly determines the needed CFM airflow capacity. Measure length x width to get accurate square footage:

  • Tiny bathrooms: 25 sq. ft. or less
  • Small bathrooms: 25-50 sq. ft.
  • Medium bathrooms: 50-100 sq. ft.
  • Large bathrooms: 100-150 sq. ft.
  • Huge bathrooms: 150+ sq. ft.

Add up all spaces if your bathroom is an irregular shape or layout.

Determine Required Airflow (CFM)

With the square footage known, match it to the recommended CFM:

  • Tiny baths: minimum 50 CFM
  • Small baths: 50-70 CFM
  • Medium baths: 70-80 CFM
  • Large baths: 80-110 CFM
  • Huge baths: 110+ CFM

Also account for special considerations:

  • Add CFM for extra humidity from jetted tubs, multi-head showers, etc.
  • Deduct CFM if the bathroom has an operable window.

Getting a fan with maximum CFM provides critical moisture removal.

Measure Physical Dimensions

Bathroom fans come in standard housing sizes:

  • 4-inch – For tiny/compact bathrooms
  • 5-inch – Fits most small to medium bathrooms
  • 6-inch – For medium to large bathrooms
  • Larger 7″-10″ – For big bathrooms

Measure your existing venting space for replacements or plan duct runs for new installs. Pick a fan that fits with at least 1-2 inches of clearance.

Match Proper CFM Fan to Right Housing

With CFM needs and physical size determined:

  • Find models offering needed CFM capacities.
  • Verify they come in a housing that fits your space.

Getting both right ensures optimal airflow and ventilation. Avoid the common mistakes of “too small” or “too big”.

Bathroom Exhaust Fan Sizing Tips

  • Carefully measure bathroom square footage using length x width. Include all spaces used.
  • Match that size to the recommend CFM level. Add CFM for extra moisture sources.
  • Physically measure ducting space or plan duct runs to determine housing sizes needed.
  • Select models with your required airflow that also come in a properly sized housing.
  • An undersized fan won’t provide enough ventilation. An oversized unit wastes energy.

Take the time to properly size your bathroom exhaust fan using CFM needs and physical dimensions. This ensures the best airflow, performance, and protection.

Bathroom Fan Ducting Guide

Proper ducting practices maximize bathroom exhaust fan efficiency. Follow this ducting guide when installing new or replacing existing bath fans.

Use Rigid Round Metal Ducts

Rigid round sheet metal ducts provide optimum airflow:

  • Smooth interior surface reduces friction/resistance.
  • Shortest distance from points A to B.
  • Does not easily crimp or collapse. Maintains interior dimensions.

Avoid vinyl, plastic or “flex ducts.” The corrugated surface traps moisture and breeds mold. They also resist airflow.

Follow Recommended Duct Sizes

Match duct diameter to the fan’s CFM rating:

  • 50-80 CFM fans = 4″ diameter duct
  • 80-120 CFM fans = 5″-6″ diameter duct
  • 120+ CFM fans = 6″-7″ diameter duct

Undersized ducts choke airflow. Oversized wastes energy heating/cooling extra air.

Minimize Duct Runs

Lengthy duct runs increase resistance and reduce airflow:

  • Use the shortest possible route to exterior.
  • Avoid unnecessary turns or curves. Use 45° angles when needed.
  • Seal all joints with aluminum tape to prevent leaks.

Keep ducts short, straight and airtight for optimal airflow.

Ensure Proper Duct Slope

Maintain at least a 1/4″ per foot downward slope:

  • Prevents condensation from pooling in duct.
  • Lets moisture run out the exit point instead of back into fan.

A descending slope drains moisture and maximizes air movement.

Install Backdraft Dampers

Backdraft dampers allow one-way airflow out while preventing outdoor air from entering the duct.

Position dampers just behind the hood termination point. Ensure they open outward to stop backdrafts.

Add Insulation

Wrap ducts with insulation in unconditioned spaces to muffle sound and prevent condensation.

Fiberglass duct wrap works well. Seal all seams and joints.

Use Proper Roof Venting

Roof vent terminations require:

  • Moisture resistant termination cap with built-in damper. Prevents leaks while letting air exit.
  • At least 18″ clearance from soffits or other roof structures. Allows proper airflow.
  • Approximately 18″ above roof surface. Prevents re-circulation of humid air.

Follow manufacturer instructions for proper roof venting.

Key Ducting Tips

  • Utilize smooth, rigid, round sheet metal ductwork only.
  • Size ducts based on fan CFM to avoid air restriction.
  • Minimize duct length and use 45° angles to reduce resistance.
  • Maintain a downward slope for condensation drainage.
  • Install backdraft dampers at exterior terminations.
  • Add insulation on ducts in unconditioned areas.
  • Position roof caps properly to maximize airflow.

Proper ducting is crucial for bathroom fans to work efficiently and effectively. Follow these best practices.

How to Choose a Bathroom Exhaust Fan

Choosing the optimal bathroom exhaust fan requires carefully weighing several factors. Follow these steps to pick the right fan for your needs and budget.

Consider Fan Placement

Determine the best positioning for proper ventilation:

  • Ceiling fans offer the most power and flexibility. They work well centered in the room or near the shower.
  • Wall fans suit smaller baths. Place them on the wall opposite the shower/tub area.

Factor in existing ductwork or easy access to exterior walls.

Measure Room Size

Calculate the bathroom’s square footage:

  • Measure length x width of entire bathroom area.
  • Include separate toilet rooms, closets etc in total size.

Accurately determining size ensures picking a fan with adequate CFM abilities.

Identify Moisture Sources

List all sources producing humidity:

  • Showers
  • Bathtubs
  • Multiple sinks
  • Hot tubs
  • High occupancy

The more moisture, the higher the CFM rating needed.

Determine Needed CFM

Use recommendations based on bathroom size:

  • Tiny baths: minimum 50 CFM
  • Small baths: 50-70 CFM
  • Medium baths: 70-80 CFM
  • Large baths: 80-110+ CFM

Also account for added humidity from fixtures when sizing up CFM needs.

Evaluate Noise Level

Factor in sound ratings when comparing models. The lower the sones, the quieter the fan.

  • Best – 0.3 to 1.0 sones
  • Good – 1.0 to 2.0 sones
  • Avoid – Over 3.0 sones

Fans with lower sones provide quiet, unobtrusive operation.

Consider Special