As stated, the most effective ventilation system for a bathroom is a mechanical one that exhausts air to the outside. This type of ventilation can be designed to remove moisture and control odors. Selecting the right fan is important, but only part of the decision. Bathroom ventilation must be considered as a system, including the fan, ducts, controls, and installation.
Many people resist using a bathroom fan because of the noise. A loud fan can be annoying, especially when using the bathroom as a stress-reducing retreat. The noise level of fans is rated in sones and fans vary in their sone rating. Generally, a fan rated less than 1.0 to 1.5 sones will be quiet enough to be considered background noise.
Choices in Bathroom Fans
Axial or propeller fans are common in bathrooms. This type of fan tends to be less expensive, but can be noisy. Centrifugal or "squirrel cage" fans are generally quieter, but can be more expensive (see Figure 7.8).
The Home Ventilating Institute (HVI) classifies bathroom fans according to the following types:
• Ceiling-mounted fans. Mounted in the ceiling between joists, this type of fan pushes air through ducts to the outside. Air can be exhausted vertically through the roof or horizontally out an exterior wall. If installing a fan in an insulated ceiling, specify a fan appropriate for this type of installation.
• Fan lights. This single fixture includes lights as well as the fan. If this type is selected, make sure that the location is optimal for both lighting and ventilation, and that the lighting is the type desired. Some fan lights may also include an infrared heater.
• Exterior-mount fans. This type of fan mounts outside the room, in either a ceiling or wall, and air is pulled through the ducts to the outside. Because the fan is mounted outside the room, these types of fans tend to be quieter.
• Inline fans. In this type of fan, the motor is mounted in the duct system. Often, inline fans are part of a whole-house ventilation system where exhaust vents are in more than one location. Keeping the fan motor out of the living space results in quieter operation.
• Wall fans. This type of fan is located on an exterior wall, and exhausts air directly to the outside without using any ducts.
• Whole-house ventilation systems. There are different types of systems that provide continuous ventilation of a house, exhausting air from it and bringing in outside air. A typical system will have an air intake in the bathroom and the fan will run continuously. More information on whole-house ventilation systems is provided below.
There are toilets on the market that are direct-vented to control odors and vapor spray from flushing. These are not likely to be adequate to control moisture from other bathroom sources. However, the exhaust venting capacity of the toilet needs to be considered in planning the total bathroom ventilation.