Selecting Bathroom Fans

Bathroom exhaust fans are important to the air quality of a home or building. They work to remove odors and prevent damage from excess moisture and heat. Before you choose between bathroom fans, there are some details to consider:

• In order to remove humidity and odors, the fan should be able to move air as much as eight air circulations per minute.
• You can choose between ceiling bath fans or wall-mount units.
• A timer or switch can be used to operate the fan.
• Some fans come equipped with light fixtures and/or heating elements.
• There are fans that are specifically designed for wet areas – like above the shower. Think about where the fan will be mounted.
• Noise is measured in sones. If you like a quiet fan, look for a model with a sone rating of .5 or less.
• Look for a reputable dealer of fans.

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Guidelines for Bathroom Ventilation

The Home Ventilation Institute(HVI) recommends that bathrooms up to 100 square feet be ventilated by intermittent or continuous ventilation with an exhaust fan that provides airflow of at least 1 Cubic Foot per Minute (CFM). For an 8×5 bathroom, a 40 CFM unit is recommended (multiply to yield the CFM: 8×5=40). Bathrooms over 100 square feet should be ventilated according to fixtures. A toilet, shower, or tub each require 50 CFM. A jetted tub requires at least 100 CFM. Each fixture is added to the total. If a bathroom has a toilet, jetted tub, and separate shower, the CFM recommendation would be 200.

To meet the CFM requirements for airflow, a single, high CFM fan – or more than one fan with smaller CFM ratings – can be installed at strategic exhaust points. Fans can be placed over or near tubs and showers, and in separate, enclosed toilet rooms. Multiple exhaust ports can also be used with an in-line fan system.

To provide the most efficient bathroom ventilation for a home or building, install bathroom fans with the minimum recommended CFM to keep heat and moisture at bay. Following these guidelines will give the maximum results when it comes to air quality and building integrity.

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Making the Most of Bathroom Exhaust

Here are some tips for making the most of bathroom exhaust:

• Be sure you have a reliable bathroom exhaust system. If your fan is an older model, look into installing an energy-efficient and quiet bathroom exhaust system for air movement and moisture removal.
• Bathroom fan exhaust points should ideally be located above or near a shower or bath tub and inside an enclosed toilet room.
• Exhaust fans should be located away from the air supply.
• Bathroom doors should be undercut to allow supply air to be pulled into the room.
• Check your ductwork for sharp turns. Maximize airflow by keeping duct pathways linear.
• Use a bathroom ventilation fan for at least 20 minutes to remove moisture and heat from the air.

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Facts About Bathroom Fans

It’s important to know some facts about bathroom exhaust ventilation before making a decision on fan installation or replacement. Here are some facts:

• Bathroom fans help maintain the structural integrity of a house by removing excess humidity that can encourage mold and rot.
• In bathrooms with windows, it is still important to install an operational exhaust system.
• The most common bath fan is a propeller or axial fan. A propeller exhaust fan can move large amounts of air without the requirement of tremendous force.
• Centrifugal fans uses centrifugal force to push air out of a space. They are more expensive than axial fans but can be more effective at air movement.
• In houses and buildings, bathroom fans ventilation ducts can run through the attic and roof. Fans can also be exhausted through walls.
• Four inch vent ducts can easily fit into a joist-bay. If a duct must pass a joist, avoid cutting through the joist. Use the space directly under the joist.
• In new construction, bathroom fans are usually a given. In many older homes, fans are either absent or retro-fitted.

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Maintaining Bathroom Exhaust Fans

Bathroom exhaust fans are designed to vent steam, hot air, and odors. Over time, fan blades can accumulate dust, debris, and moisture, creating stress on the exhaust motor. There are a few simple things you can do to maintain your bathroom fan exhaust system to keep it from being noisy and burning out:

• Remove the fan cover.
• Unplug the fan from the housing unit.
• Remove the fan and motor and clean the fan blades and blower wheel. Shake off excess water and dry with a towel.
• Avoid getting the motor wet.
• Put six drops of household motor oil in the oil ports and put the fan and motor back in place.
• Clean the front cover with warm, soapy water or a soft scrubbing solution. Dry and put the cover back in place.
• Read the manufacturer’s instructions for cleaning and maintenance. Some fans require more specific maintenance.

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Testing Your Bathroom Fan

To find out if your bathroom ventilation fan is working properly, follow these steps:

• Turn the fan on and hold a tissue to the grill of the fan. If the tissue is held to the grill by the fan, then the fan is doing its job drawing air through the ventilation duct.
• To be sure that air is being exhausted properly, check the exhaust hood from the outside. Turn on the fan and place the open end of a plastic bag over the exhaust hood. An inflated bag is a sign that the air is being exhausted properly.
• If your fan is not drawing air or exhausting properly, you may need to replace the fan motor.
• Keep in mind that a bathroom fan should exhaust at a rate of at least 1 CFM (cubic feet per minute) per square foot. Bathrooms with large fixtures need more powerful or additional fans to vent air properly.
• Poor ductwork placement may also be responsible for exhaust malfunction.

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Bathroom Fan Ratings

Exhaust fans are essential to building ventilation. They help to lower energy costs and remove excess moisture. Here are some tips on ratings and replacement:

• If you plan to replace an existing fan, look for one with an air movement rating of 50 CFM (cubic feet per minute) or more.
• A 120 volt heater is ideal for home bathrooms – 250 volt units are designed for larger spaces and require special wiring.
• Before replacing a bathroom ventilation fan, be sure the existing circuit can handle the amperage of the fan.
• Measure to see if the new exhaust heater is big enough to cover the hole left by the old unit. Do not install a fan with a heater over the bathtub or shower.
• Make the most of your time and money. Look for bathroom exhaust heaters that have built-in lighting.

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The Benefits of Inline Bathroom Fans

In-line fans are installed in attic space rather than being wall- or ceiling-mounted like standard bathroom fans. Here are some of the benefits of installing in-line fans:

• With in-line fans, there are fewer limitations when it comes to placement.
• Because in-line bathroom exhaust systems can be installed anywhere in the attic, they are a great way to achieve quiet bathroom exhaust.
• An in-line fan ventilation system can be used for adjoining bathrooms or for multiple exhaust points in one larger bathroom.
• Inline exhaust can be used when ductwork is too long for efficient exhausting.
• They provide powerful venting for efficient moisture removal.
• In-line fans have a reputation for long-lived motors.
• In-line fans work efficiently to to provide successful home ventilation, preserving building and home integrity.

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Installation Safety

If you plan to install or replace a bathroom fan or bathroom exhaust heater, there are some things to know about electricity and safety:

• Find out if you need a permit or certified electrician to do the work.
• Before working with electricity, turn off the power.
• Make sure the power is off – test the wires with a voltage meter.
• To safeguard against accidents, lock the panel box to keep anyone from turning the power on while you work.
• Wear safety goggles and a dust mask for protection.
• Follow manufacturer’s installation instructions.
• Don’t overload the circuit. Size your equipment per circuit amperage limits.

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Bathroom Fans and Noise

The noise of exhaust fans is typically measured in sones. An extremely quiet bathroom fan will have a sone rating of 1.0 or lower, where a sone rating of 4.0 is extremely noisy. There are several more factors that can cause noisy bathroom fan exhaust:

• In-duct fans tend to be quieter than ceiling mounted fans.
• The location of bathroom exhaust vents and the configuration of ductwork can cause fans to be noisy. Keep venting turns gradual. Do not create sharp bends in the ductwork.
• Larger venting will keep fans quieter. Use four inch venting rather than three inch venting.
• Rigid piping transmits more noise than flexible duct work. Look for noise-muffling duct materials.
• Using nails instead of screws in fan installation can create noise once the nails begin to loosen and vibrate.
• Keep the bathroom fan clean. Dirt and debris can accumulate over time to keep your fan from operating efficiently.
• Consider installing a bath fan with a timer to keep fans from running longer than 20 minutes.

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