Without adequate ventilation, your bathroom is at risk for long-term damage to walls, ceiling, flooring, and trim from mold, mildew, and rot. But choosing a bathroom exhaust fan often presents a paradox: You want a powerful fan but not one that is so loud that no one will use it. On the other hand, if you bring down the noise levels to near-silence, is the fan doing its job well enough?
What Is a Bathroom Exhaust Fan?
Bathroom exhaust fans are usually placed near or in the ceiling of a bathroom. They are necessary for expelling odors and for keeping moisture levels in check.
Noise and efficiency do not always equate. The perfect bathroom fan is both quiet and has sufficient room-clearing capability. Cost also must be figured into the decision, as few consumers wish to buy a quiet, efficient fan if it costs a fortune. A few bathroom fans strike a good balance between capacity, noise rating, and cost.
Best Quiet Bathroom Exhaust Fans
The Panasonic FV-30VQ3 WhisperCeiling is a high capacity exhaust fan so quiet that homeowners report that they need to install timers because they forget that the fan is on. WhisperCeiling strikes the perfect balance between quietness and capacity.
- CFM: 290
- Sones: 2.0
- CFM-Per-Sone: 0.0069
- Price Range: $200 to $250
Broan QTXE080 QTX Series Very Quiet
Broan is a long-established maker of fans, heaters, and range hoods. Their QTX Very Quiet bathroom exhaust fan is dead-quiet at 0.3 sones, one of the quietest bathroom fans you can buy. But you do pay the cost in terms of low volume. If you don't need a high capacity fan and noise is important to you, the Broan Very Quiet might be right for your bathroom. One other factor that may seal the deal for you is that the QTX Very Quiet is less than half the price of the other exhaust fans here.
- CFM: 80
- Sones: 0.3
- CFM-Per-Sone: 0.0038
- Cost: $100 to $125
NuTone QT300 High Capacity Fan
NuTone's QT300 is truly a high capacity fan, as its name says. It is intended for large spaces such as master bathrooms, commercial restrooms, conference rooms, and other public spaces.
- CFM: 300
- Sones: 4.5
- CFM-Per-Sone: 0.0150
- Cost: $225 to $275
Measuring Bathroom Exhaust Fan Sound Levels
Sones, not decibels, are the industry-accepted units of measurement used when evaluating noise levels for bathroom fans. Sones are a subjective measurement, based on the psychological perception of a sound's intensity. Single-speed bathroom fans range from 0.3 sones or less for the very quietest models to 4.0 sones or more for the loudest economy models.
Measuring Air Movement
As a general rule, a bathroom should have an exhaust fan that pulls out a minimum of 50 CFM or greater. To take full advantage of your fan's cubic foot per minute capability, it helps to supply enough intake, or makeup, air by leaving the bathroom door slightly open while the fan is running. Fans don't just expel bad air; they create air exchange by pulling in the fresh air at the same time. If you starve the fan of makeup air, it won't do its job very well. You can crack the door open after using the toilet or taking a shower.
Efficiency Per Sone Rating
Ideally, it is best to have a fan that sucks out massive amounts of air at a lower noise cost, much like a car that goes farther on less fuel. While noise and efficiency do not perfectly equate, there is still a rough correlation between the two factors. Sones do generally increase as air volume increases; think of the sound of a range fan or household fan increasing as you move up each level of volume. With bathroom exhaust fans, most of the < 0.3-sone fans move 80 CFM or less, while most of the 1.0-sone and louder fans move 140 CFM or more. But it is not quite that simple. Sometimes, a few outliers move more air with less noise.
One way to evaluate the data and better standardize CFM and noise is to bring the two numbers together. The intersection between sones and air volume (dividing sones by CFM) gives you a better view of a bathroom fan's value than just by looking at noise or volume alone. Lower CFM-per-sone numbers are better. For example, a fan rated at 1 sone and 1 CFM would produce a CFM-per-sone rating of 1. If a fan with the same sones were able to pull out 2 CFM, its CFM-per-sone rating would be 0.5.
As an extreme example, consider one popular bargain bathroom exhaust fan that has a noise level of a whopping 4.0 sones, yet it expels only 50 CFM. Its CFM-per-sone rating is 0.0800, about 20 times less efficient on a CFM-per-sone basis than the WhisperQuiet and higher than most other bathroom fans on the market.
Another bathroom exhaust fan, of the type purchased by commercial establishments, pulls 470 CFM at the cost of 8.0 sones. Its sone-to-CFM rating is 0.0170, which is far lower than the previous bargain fan.
The last dimension to consider when purchasing a quiet bathroom fan is its cost. A super-quiet bathroom fan may not be worth purchasing if it is beyond your remodeling budget. Yet an ultra-cheap bathroom fan might be so loud that it rarely gets used. For example, the Broan 688 is a workhorse that contractors have been installing in bathrooms for many years. If you are looking for an inexpensive and dependable exhaust fan, the Broan 688 might be right for you. Its price has remained the same over the last five years. Yet, at 4.0 sones, quiet it is not.