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Continuous Supply/Exhaust Fan Ratings

    Scope
    Scope Images
    Image
    Intermittent supply and exhaust fans rated at ≤ 3 sones by manufacturer, unless rated flow ≥ 400 CFM
    Scope

    For continuous supply or exhaust fans, select quiet fans with a sone rating of 1.0 or less. The sone rating should be listed on the product label or in the manufacturer's license.

    See the Compliance Tab for links to related codes and standards and voluntary federal energy-efficiency program requirements.

    Description
    Description

    To meet ASHRAE 62.2 ventilation requirements, the HVAC designer may specify that an exhaust fan should be set for continuous operation. Fans that are overly noisy are more likely to be turned off by the home owner, circumventing the fan’s intended purpose of providing required whole-house ventilation. To encourage continual use, quiet fans should be specified and installed. Fan noise is measured in sones; the lower the sone, the quieter the fan. Exhaust or supply fans installed for continuous use should have a sone rating of 1.0 sones or less. For comparison, a quiet refrigerator operates at about 1.0 sone.

    Fans exempted from this requirement include HVAC air handlers, and remote-mounted fans. To be considered exempt, a remote-mounted fan must be mounted outside the habitable spaces, including bathrooms and hallways, and there must be at least 4 feet of ductwork between the fan and intake grill.

    For more on continuously operating exhaust fans and ASHRAE 62.2 requirements, see Continuously Operating Ventilation and Exhaust Fans.

    How to Select 1.0 Sone Supply and Exhaust Fans

    1. When specifying and purchasing bathroom fans that will be exhaust or supply fans that will be used continuously, select quiet fans with a sone rating of 1.0 or less. The sone rating should be listed on the product label or in the manufacturer’s literature.
    The manufacturer’s label found on this exhaust fan housing shows a sone rating of 1.0.
    Figure 1. The manufacturer’s label found on this exhaust fan housing shows a sone rating of 1.0.

     

    Success
    Ensuring Success

    In homes where an exhaust or supply fan is installed that will operate continuously, the HERS rater should inspect to ensure that the fan’s noise level is rated at less than or equal to 1.0 sone by the manufacturer.

    Climate
    Climate

    No climate specific information applies.

    Training
    Right and Wrong Images
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    Sone rating is greater than 3.0
    Sone rating is greater than 3.0
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    Sone rating is 3.0 for this intermittent exhaust fan
    Sone rating is 3.0 for this intermittent exhaust fan
    Image
    Sone rating is greater than 1 on a continuous exhaust fan
    Sone rating is greater than 1 on a continuous exhaust fan
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    Sone rating is less than or equal to 1 on a continuous exhaust fan
    Sone rating is less than or equal to 1 on a continuous exhaust fan
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    The fan does not have an ENERGY STAR label
    The fan does not have an ENERGY STAR label
    Image
    The fan does have an ENERGY STAR label
    The fan does have an ENERGY STAR label
    Compliance
    More

    More Info.

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    References and Resources*
    Author(s)
    ENERGY STAR
    Organization(s)
    U.S. Department of Energy,
    DOE,
    ENERGY STAR
    Publication Date
    Description
    Factsheet describing the benefits of purchasing and installing ENERGY STAR rated fans and ventilation products.
    Author(s)
    American Society of Heating Refrigeration and Air-Conditioning Engineers
    Organization(s)
    ASHRAE,
    ANSI
    Publication Date
    Description
    Standard that defines the roles of and minimum requirements for mechanical and natural ventilation systems and the building envelope intended to provide acceptable indoor air quality in low-rise residential buildings. This version of the standard was published in the year 2010, and is available for...
    *For non-dated media, such as websites, the date listed is the date accessed.
    Contributors to this Guide

    The following authors and organizations contributed to the content in this Guide.

    Sales
    Building Science Measures
    Building Science-to-Sales Translator

    High-Efficiency Fans = High-Efficiency Fans

    Image(s)
    Technical Description

    High-efficiency exhaust fans and ceiling fans are more energy efficient and quieter than standard fans.

    High-Efficiency Fans
    Sales Message

    High-efficiency fans minimize the wasted energy exhausting air while being virtually silent. What this means to you is odors and contaminants are efficiently removed without the noise. Isn’t it time homes used advanced technology components?

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