Intermittent Supply/Exhaust Fan Ratings

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

    For intermittent supply or exhaust fans, select quiet fans with a sone rating of 3.0 or less. The sone rating should be listed on the product label or in the manufacturer's license.

    See the Compliance Tab for related codes and standards requirements, and criteria to meet national programs such as DOE’s Zero Energy Ready Home program, ENERGY STAR Certified Homes, and Indoor airPLUS.

    Description

    Exhaust fans are often installed in bathrooms, kitchens, and laundry rooms to provide intermittent, localized ventilation. Fans that are overly noisy are more likely to be turned off quickly, perhaps too quickly to work effectively, for example to remove all the moisture in the bathroom after a shower or in the kitchen after boiling water. To improve indoor air quality and moisture control, 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 intermittent use should have a sone rating of 3 or less. For comparison, a quiet refrigerator operates at about 1.0 sones.

    Fans exempted from this requirement include fans with a rated flow rate equal to or greater than 400 CFM, 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 grille.

    For more on exhaust fan ratings, see Continuous Supply/Exhaust Fan Ratings and Bathroom Fan Ratings.

    How to Select Low-Sone Supply and Exhaust Fans

    1. When specifying and purchasing exhaust or supply fans that will be used intermittently for local exhaust within the home, select quiet fans with a sone rating of 3.0 or less. The sone rating should be listed on the product label or in the manufacturer’s literature.
    Manufactures label found on exhaust fan housing shows sone rating of 2.5
    Figure 1. The manufacturer’s label found on this exhaust fan housing shows a sone rating of 2.5. (Source: PNNL).
    Ensuring Success

    In homes where a fan is installed to provide intermittent supply or exhaust, the HERS rater should inspect to ensure that the fan’s noise level is rated at less than or equal to 3.0 sones by the manufacturer (not required on fans with flow rates equal to or greater than 400 cubic feet per minute).

    Climate

    No climate specific information applies.

    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
    Image
    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
    Image
    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

    The Compliance tab contains both program and code information. Code language is excerpted and summarized below. For exact code language, refer to the applicable code, which may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

     

    ENERGY STAR Certified Homes, Version 3/3.1 (Rev. 09)

    National Rater Field Checklist

    HVAC System.
    7. Whole-House Mechanical Ventilation System.
    7.4 System fan rated ≤ 3 sones if intermittent and ≤ 1 sone if continuous, or exempted.44

    8. Local Mechanical Exhaust - In each kitchen and bathroom, a system is installed that exhausts directly to the outdoors and meets one of the following Rater-measured airflow and manufacturer-rated sound level standards:42, 48

    National Rater Field Checklist: Local Mechanical Exhaust.
    National Rater Field Checklist: Local Mechanical Exhaust. (Source: ENERGY STAR Certified Homes, Version (Rev. 09))

     

    Footnote 42) The whole-house ventilation air flow and local exhaust air flows shall be determined and documented by a Rater using the same version of ANSI / RESNET / ICC Std. 380 that is utilized by RESNET for HERS ratings.

    Footnote 44) Whole-house mechanical ventilation fans shall be rated for sound at no less than the airflow rate in Item 2.3 of the National HVAC Design Report. Fans exempted from this requirement include HVAC air handler fans, remote-mounted fans, and intermittent fans rated ≥ 400 CFM. To be considered for this exemption, a remote-mounted fan must be mounted outside the habitable spaces, bathrooms, toilets, and hallways and there shall be ≥ 4 ft. ductwork between the fan and intake grill. Per ASHRAE 62.2-2010, habitable spaces are intended for continual human occupancy; such space generally includes areas used for living, sleeping, dining, and cooking but does not generally include bathrooms, toilets, hallways, storage areas, closets, or utility rooms.

    Footnote 48) Continuous bathroom local mechanical exhaust fans shall be rated for sound at no less than the airflow rate in Item 8.2. Intermittent bathroom and both intermittent and continuous kitchen local mechanical exhaust fans are recommended, but not required, to be rated for sound at no less than the airflow rate in Items 8.1 and 8.2. Per ASHRAE 62.2-2010, an exhaust system is one or more fans that remove air from the building, causing outdoor air to enter by ventilation inlets or normal leakage paths through the building envelope (e.g., bath exhaust fans, range hoods, clothes dryers). Per ASHRAE 62.2-2010, a bathroom is any room containing a bathtub, shower, spa, or similar source of moisture.

    Footnote 49) An intermittent mechanical exhaust system, where provided, shall be designed to operate as needed by the occupant. Control devices shall not impede occupant control in intermittent systems.

    Footnote 50) Kitchen volume shall be determined by drawing the smallest possible rectangle on the floor plan that encompasses all cabinets, pantries, islands, peninsulas, ranges / ovens, and the kitchen exhaust fan, and multiplying by the average ceiling height for this area. In addition, the continuous kitchen exhaust rate shall be ≥ 25 CFM, per 2009 IRC Table M1507.3, regardless of the rate calculated using the kitchen volume. Cabinet volume shall be included in the kitchen volume.

    Footnote 51) For homes permitted through 01/01/2014: Homes are permitted to be certified without enforcement of this Item to provide partners with additional time to integrate this feature into their homes.
    For homes permitted on or after 01/01/2014: Homes shall meet this Item. Alternatively, the prescriptive duct sizing requirements in Table 5.3 of ASHRAE 62.2-2010 / 2013 / 2016 are permitted to be used for kitchen exhaust fans based upon the rated airflow of the fan at 0.25 IWC. If the rated airflow is unknown, ≥ 6 in. smooth duct shall be used, with a rectangular to round duct transition as needed. Guidance to assist partners with these alternatives is available at energystar.gov/newhomesresources. As an alternative to Item 8.1, homes are permitted to use a continuous kitchen exhaust rate of 25 CFM per 2009 IRC Table M1507.3, if they are either a) PHIUS+ or PHI certified, or b) provide both whole-house ventilation and local mechanical kitchen exhaust using a balanced system, and have a Rater-verified whole-building infiltration rate ≤ 0.05 CFM50 per sq. ft. of Enclosure Area, and a Rater-verified dwelling unit compartmentalization rate ≤ 0.30 CFM50 per sq. ft. of Enclosure Area if multiple dwelling units are present in the building. ‘Enclosure Area’ is defined as the area of the surfaces that bound the volume being pressurized / depressurized during the test.

    Footnote 52) All intermittent kitchen exhaust fans must be capable of exhausting at least 100 CFM. In addition, if the fan is not part of a vented range hood or appliance-range hood combination (i.e., if the fan is not integrated with the range), then it must also be capable of exhausting ≥ 5 ACH, based on the kitchen volume.

    Please see the ENERGY STAR Certified Homes Implementation Timeline for the program version and revision currently applicable in in your state.

     

    DOE Zero Energy Ready Home (Revision 07)

    Exhibit 1 Mandatory Requirements.
    Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program

     

    2009 International Energy Conservation Code (IECC)

    This topic is not specifically addressed in the 2009 IECC.

    2012 IECC

    Section R403.5.1 Whole-house mechanical ventilation system fan efficacy. Mechanical ventilation system fans shall meet the efficacy requirements of Table R403.5.1  

    2015 and 2018 IECC

    Section R403.6.1 Whole-house mechanical ventilation system fan efficacy. Mechanical ventilation system fans shall meet the efficacy requirements of Table R403.6.1.  

    2021 IECC

    Section R403.6.2 Whole-house mechanical ventilation system fan efficacy. Mechanical ventilation system fans shall meet the efficacy requirements of Table 403.6.2 at one or more rating points.  Fans shall be tested in accordance with HVI 916 and listed and the airflow shall be reported in the product listing or on the label. Fan efficacy for fully ducted HRV, ERC, balanced, and in-line fans shall be determined at a static pressure of not less than 0.2 inch w.c. (49.85Pa). Fan efficacy for ducted range hoods, bathroom and utility room fans shall be determined at a static pressure of not less than 0.1 inch w.c. (24.91Pa).

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IECC

    Section R101.4.3 (in 2009 and 2012). Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with this code. (See code for additional requirements and exceptions.)

    Chapter 5 (in 2015, 2018, 2021). The provisions of this chapter shall control the alteration, repair, addition, and change of occupancy of existing buildings and structures.

     

    2009 International Residential Code (IRC)

    This topic is not specifically addressed in the 2009 IRC.

    2012, 2015, 2018,  and 2021 IRC

    Section N1103.6 (N1103.5 in 2012 IRC) Mechanical ventilation. Buildings and dwelling units shall be provided with mechanical ventilation that complies with the requirements of Section M1505 or with other approved means of ventilation. Outdoor air intakes and exhausts shall have automatic or gravity dampers that close when the ventilation system is not operating. Fans shall meet the efficacy requirements of Table N1103.6.2 2021 (N1103.6.1 2018 and 2015 IRC and N1103.5.1 in 2012 IRC).

    Retrofit:  2009, 2012, 2015, 2018,  and 2021 IRC

    Section R102.7.1 Additions, alterations, or repairs. Additions, alterations, renovations, or repairs shall conform to the provisions of this code, without requiring the unaltered portions of the existing building to comply with the requirements of this code, unless otherwise stated. (See code for additional requirements and exceptions.)

    Appendix J regulates the repair, renovation, alteration, and reconstruction of existing buildings and is intended to encourage their continued safe use.

     

    American National Standards Institute (ANSI)/American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) Standard 62.2.-2010

    Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings.  The standard applies to spaces intended for human occupancy in single-family homes and multifamily homes that are three stories or less, including manufactured and modular homes.  The standard provides minimum acceptable requirements for mechanical and natural ventilation in these spaces. 

    More Info.

    Access to some references may require purchase from the publisher. While we continually update our database, links may have changed since posting. Please contact our webmaster if you find broken links.

    References and Resources*
    Author(s)
    Department of Energy,
    U.S. Environmental Protection Agency
    Organization(s)
    DOE,
    EPA
    Publication Date
    Description
    Information sheet about the benefits of purchasing and installing ENERGY STAR rated fans and ventilation products.
    *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.

    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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