Breathe Easy

What you need to know to ensure proper home ventilation
By Patrick Nielsen
September 14, 2011

Natural ventilation used to be the best way to allow fresh outdoor air to replace contaminated indoor air in a home. But because today’s energy-efficient homes are air-sealed and built more tightly for heating and cooling control, it’s essential to have a mechanical ventilation strategy for today’s homes.

To maintain a safe and comfortable indoor environment, we must now mechanically ensure that contaminants—humidity, odors, dust, pet dander, grease, mold, formaldehyde and other chemicals—are constantly removed from the building. A proper ventilation system maintains indoor air quality and reduces the probability of mold formation.

There are two general types of ventilation: local (or spot) and whole-house.


Spot ventilation focuses on removing contaminants from a specific place at a specific time, such as the ventilating fan in a bathroom that helps eliminate steamy mirrors, foggy windows and stale odors. Architects, builders and designers should consider a number of factors when installing a bath fan for spot ventilation use.

The Home Ventilating Institute (HVI) recommends that fans should have airflow of roughly 1 cubic foot per minute (cfm) for every square foot of a bathroom area up to 100 ft. For bathrooms larger than this, HVI recommends a ventilation rate based on the fixtures present in the bathroom, with a basis of adding together 50 cfm for each traditional appliance (toilet, shower and so on) and 100 cfm for larger items such as a jetted tub. If additional showerheads are installed, additional or increased ventilation should also be installed. These are rules of thumb—generally, more cfm will take care of issues faster.

The loudness of the fan is also important to consider. Sound levels in fans are measured in sones, with lower numbers being quieter. A typical builder-grade fan is 4.0 sones while any fan rated at 1 sone or less is very quiet (1 sone is roughly the equivalent sound of a quiet refrigerator in a quiet room).
Humidity-sensing fans that have the sensor incorporated right into the fan itself, such as this one from Broan-NuTone, detect humidity at the ceiling where it is the most concentrated.

The HVI recommends that a fan remain on for a minimum of 20 minutes after each use of the shower or bath. Using a timer can help ensure that the bath fan is on for the allotted time needed. For those of us who may be hesitant to turn on the fan for fear of forgetting to turn it off, timers are great alternatives. Another great substitute to a fan switch is a humidity-sensing fan, which automatically turns ON when humidity rises and then turns OFF when the humidity returns to normal. This is a great solution for a bathroom used by the kids, who are notorious for forgetting to turn on the fan. Some models that have the sensor incorporated right into the fan itself are particularly effective as they sense humidity at the ceiling, where it is the most concentrated, and are triggered by a change in humidity over time rather than a set humidity level. These fans are also adjustable in terms of sensitivity and time delay.

Bath fan/light combinations are another great option. A builder can complete two remodeling tasks, lighting and ventilation, with one unit, and homeowners are always eager for a product that can fix multiple household issues at once. Many of these bath fan/lights come in decorative models that blend with existing fixtures but are actually fully functional ventilation fans. On top of that, they’re very easy to install. A fan/light can be installed in the same footprint of the existing fan, which means you can use the original wiring and wall switch.

Many decorative models go well beyond the traditional bath fan/light. NuTone’s LunAura Collection of ventilation fan/lights (shown) incorporates blue LEDs that lend an atmosphere of calm.


Many building codes and green building standards, such as LEED and Energy Star, are increasingly requiring whole-house ventilation. Whole-house ventilation systems provide controlled ventilation throughout an entire home.

A good quality bath ventilation fan can be a two-for-one solution for both spot and whole-house ventilation needs. Such a fan must be powerful enough to meet both the needs of the bathroom where it is located and the level of air movement that the whole-house requirement necessitates. The amount of cfm needed for the whole-house component depends on the square footage and number of bedrooms in the home.

Because whole-house fans will run more often than spot fans, it’s essential that they be extremely quiet. In fact, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) 62.2 standard requires that whole-house fans be rated at 1.0 sones or less. No one likes to be awakened at night by a loud fan running in an otherwise quiet home.

Although choosing an Energy Star-qualified fan is always a good idea, it is even more important for whole-house fans due to their frequency of use. Some of the best fans on the market in terms of overall quality, quiet operation and styling are also the most energy efficient. Energy Star fans use up to 65 percent less energy than standard fans.


Beyond your basic ventilation needs, there are a number of other functions, features and styles available in today’s ventilation fans, including nightlights and heaters. Heaters in bathrooms are perhaps the most popular option, because they deliver heat exactly when and where it is needed in the morning, meaning that the homeowner doesn’t have to turn up the thermostat for the entire house.

Innovations in bathroom and home ventilation are making household living more comfortable than ever before. Whether you’re looking to clear the air in a bathroom after a long shower or freshen up your entire home, builders, remodelers and designers can offer homeowners exactly what they need to let the home breathe, and to let the homeowner breathe easy.

—Patrick Nielsen is marketing manager, ventilation fans, at Broan-NuTone.
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