4.506.1 Bathroom exhaust fans. Each bathroom shall be mechanically ventilated and shall comply with the following:
1. Fans shall be ENERGY STAR compliant and be ducted to terminate outside the building.
2. Unless functioning as a component of a whole house ventilation system, fans must be controlled by a humidity control.
a. Humidity controls shall be capable of adjustment between a relative humidity range of ≤ 50 percent to a maximum of 80 percent. A humidity control may utilize manual or automatic means of adjustment.
b. A humidity control may be a separate component to the exhaust fan and is not required to be integral (i.e., built-in).
Notes:
1. For the purposes of this section, a bathroom is a room which contains a bathtub, shower, or tub/shower combination.
2. Lighting integral to bathroom exhaust fans shall comply with the California Energy Code.
COMMENTARY
Purpose:
The functions of a bathroom exhaust fan are to exhaust odors and excess humidity. This mandatory measure is intended to reduce moisture inside the residence through use of bathroom exhaust fans controlled by humidity sensing devices.
Examples of Acceptable Methods of Implementation and/or Compliance:
Install ENERGY STAR fans with humidity controls in each bathroom. Humidity controls for exhaust fans may be integrated in (built-in) or external to the exhaust fan units. Manual or automatic controls capable of adjusting for relative humidity of less than 50% are acceptable. The maximum relative humidity setting allowed is 80 percent.
Install a fan in compliance with ASHRAE 62.2 “Ventilation and Acceptable Indoor Air quality in Low-Rise Residential Buildings” and Title 24, Part 6, in the bathroom that is a part of a whole house ventilation system.
Background:
Excess moisture in the interior areas of buildings can lead to condensation, which promotes the growth of mold and may cause structural problems such as dry rot, warping of wood, etc.
Humidistats are sensors detecting the amount of moisture in the air. Humidistats can also be used as controllers to switch fans on or off when moisture levels exceed a designated range. Humidity control devices allow the humidity settings to be adjustable from 20 to 80 percent relative humidity and may be an integral component of the fan or may be external to the fan.
Humidity controls for bathroom exhaust fans ensure that fans continue to run until moisture levels
in the bathroom fall to desired levels depending on local conditions and personal comfort levels. Often this may be more than 20 minutes after the bathroom is vacated.
ENERGY STAR states that “Qualified ventilation fans use 70 percent less energy than standard models. These fans provide better efficiency and comfort with less noise, and use high performance motors that work better and last longer than motors used in conventional models. They feature high performance motors and improved blade design, providing better performance and longer life.”
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