Intermittent Supply/Exhaust Fan Ratings

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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 (Image Courtesy of 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).

Scope

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

Local Mechanical Exhaust

Intermittent supply and exhaust fans rated at <= 3 sones by manufacturer, unless rated flow >= 400 CFM

  1. Install fans rated by the manufacturer at 3 sones or less.
  2. If the fan has a rated flow equal to or above 400 CFM, the requirement described in “A” does not apply.

ENERGY STAR Notes:

Fans exempted from this requirement include kitchen exhaust fans, HVAC air handler fans, and remote-mounted fans. 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.

Training

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Compliance

ENERGY STAR Version 3, (Rev. 07)

HVAC System Quality Checklist, Ventilation & Exhaust Fan Ratings (Exemptions for HVAC and Remote-Mounted Fans). Intermittent supply and exhaust fans rated at <= 3 sones by manufacturer when producing no less than the minimum airflow rate required by Section 8 of the checklist, unless rated flow >= 400 CFM. Fans exempted from this requirement include HVAC air handlers and remote-mounted fans. 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 feet of 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.

DOE Challenge Home

Exhibit 1: Mandatory Requirements. Certified under ENERGY STAR Qualified Homes Version 3.

ANSI/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. 

2009 IECC

This topic is not specifically addressed in the 2009 IECC.

2009 IRC

This topic is not specifically addressed in the 2009 IRC.

2012 IECC

This topic is not specifically addressed in the 2012 IECC. 

2012 IRC

This topic is not specifically addressed in the 2012 IRC.

More Info.

Case Studies

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References and Resources*

  1. Author(s): ASHRAE
    Organization(s): ASHRAE
    Publication Date: January 2013

    Standard defining 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.

  2. Author(s): DOE
    Organization(s): DOE
    Publication Date: June 2013

    Standard requirements for DOE's Challenge Home national program certification.

  3. Author(s): EPA
    Organization(s): EPA
    Publication Date: June 2013

    Standard document containing the rater checklists and national program requirements for ENERGY STAR Certified Homes, Version 3 (Rev. 7).

  4. Author(s): DOE, EPA
    Organization(s): DOE, EPA
    Publication Date: January 2013

    Information sheet about the benefits of purchasing and installing ENERGY STAR rated fans and ventilation products.

Last Updated: 08/15/2013

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