Continuous Supply/Exhaust Fan Ratings

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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 sones.

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.  Reference

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.

Scope

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

Local Mechanical Exhaust

Continuous supply and exhaust fans rated at <= 1 sone by manufacturer

  1. Install fans rated by the manufacturer at 1 sones or less.

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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Presentations

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CAD Images

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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). 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.

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

None Available

References and Resources*

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

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

  2. 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).

  3. 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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