Continuously Operating Ventilation and Exhaust Fans

    Scope Images
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    Continuously-operating ventilation & exhaust fans include readily accessible override controls
    Continuously-operating ventilation & exhaust fans include readily accessible override controls
    Scope

    Install readily accessible override controls for ventilation fans and exhaust fans that are set for continuous operation to meet ventilation code requirements.

    • Locate the controls in one of three places:
      • near the thermostat 
      • on the electrical panel 
      • on the switch plate or on or near the air handler.
    • Identify the override control switch with a label and provide instructions for its use.

    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 Single-Family New Homes, and Indoor airPLUS.

    Description

    To meet ASHRAE 62.2 ventilation requirements, the HVAC designer may specify that an exhaust fan should be set for continuous operation. In homes with continuously operating ventilation and exhaust fans, it is important for HVAC contractors and electricians to select fans that have override controls and that they locate the override controls in a location easily accessible to the homeowner. It is also important to properly label these controls. If controls are not properly labeled, fans may be mistakenly turned off.

    For more on continuously operating exhaust fans and ASHRAE 62.2 requirements, see Obvious Ventilation Controls, Bathroom Exhaust Fans, Continuous Supply/Exhaust Fan Ratings, and Bathroom Fan Ratings.

    How to Locate the Override Controls

    The installer has three options for locating the override controls:

    1. Locate the labeled control switch on a wall next to the thermostat. This creates a control center for the homeowner, allowing the homeowner to access the majority of the HVAC system controls in one place. This setup is ideal for ventilation systems, such as ERVs and HRVs that may be located in inaccessible places.
      The ventilation controller is next to the thermostat and has a manual override button.
      Figure 1. The ventilation controller is located next to the thermostat creating a control center for the homeowner. The ventilation controller has a manual override button.
    2. Locate a switch on the electrical panel with a label. In a house with multiple continuously running exhaust fans, all of the fans can be wired to one switch on the electrical panel. Because the switch is out of sight, although easily accessible, this option can help prevent the fans from being accidentally turned off.
      All of the exhaust fans are wired to one labeled switch at the electrical panel.
      Figure 2. In a home with several exhaust fans, all of the fans can be wired to one labeled switch at the electrical panel.
    3. Exhaust fan models that have an internal override system, either on the electrical switch plate or as defined in the manufacturer’s manual, can meet the requirement as long as the override is accessible. Figure 3 shows a ventilation controller for a central air handler fan. Figure 4 shows a bath exhaust fan ventilation controller that is installed in the outlet box under the switch plate. It can be set by the HVAC technician for continuous operation, delayed shut off, or a set amount of minutes each hour. The fan will run continuously or automatically come on once per hour for the set ventilation time. The occupant moves the toggle switch up to turn on the fan and light and down to turn the light off. The fan will run continuously or for a set delay time to meet the required ventilation amount. Any manual fan operation and delay operation will be subtracted from the ventilation time for that hour. To override or cancel the delay time, the occupants can move the toggle up again for at least 1 second then down again. The fan will shut off, canceling the set delay time.
      A ventilation controller with a manual override is located on a central air handler fan that is located in an accessible location.
      Figure 3. This ventilation controller, which has an obvious override switch, is located on a central air handler fan that is located in an accessible location.
      Bath exhaust fan ventilation control can be set by the HVAC technician for continuous operation, delayed shut off, or a set amount of minutes each hour.
      Figure 4. This bath exhaust fan ventilation control can be set by the HVAC technician for continuous operation, delayed shut off, or a set amount of minutes each hour. To override the delay time, move toggle up again for at least 1 second then down again, to shut off the fan, canceling the set delay time.

     

    Ensuring Success

    In homes with continuously operating ventilation and exhaust fans, the HERS rater should inspect to ensure that the fans include readily accessible override controls.

    Climate

    No climate specific information applies.

    Right and Wrong Images
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    Override control switches centrally located near thermostat for ease of access
    Override control switches centrally located near thermostat for ease of access
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    Right – An ERV provides filtered fresh air to this small home.
    Right – An ERV provides filtered fresh air to this small home.
    Image
    Right – This bath fan runs continuously at low speed and is activated by a motion sensor to operate a higher speeds.
    Right – This bath fan runs continuously at low speed and is activated by a motion sensor to operate a higher speeds.
    Image
    Right – This energy recovery ventilator provides fresh air and exhausts stale air through a heat exchanger that recovers heat from the outgoing air in winter and reduces heat from incoming air in the summer to provide ventilation without wasting energy.
    Right – This energy recovery ventilator provides fresh air and exhausts stale air through a heat exchanger that recovers heat from the outgoing air in winter and reduces heat from incoming air in the summer to provide ventilation without wasting energy.

    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 Single-Family New Homes, Version 3/3.1 (Rev. 11)

    National Rater Field Checklist

    HVAC System.
    7. Dwelling Unit Mechanical Ventilation Systems (“Vent System”) 45 & Inlets In Return Duct 46
    7.2 A readily-accessible ventilation override control installed and also labeled if its function is not obvious (e.g., a label is required for a toggle wall switch, but not for a switch that’s on the ventilation equipment).48

    Footnote 45) As defined by ANSI / RESNET / ICC Std. 301-2019, a Dwelling Unit Mechanical Ventilation System is a ventilation system consisting of powered ventilation equipment such as motor-driven fans and blowers and related mechanical components such as ducts, inlets, dampers, filters and associated control devices that provides dwelling-unit ventilation at a known or measured airflow rate.

    Footnote 46) Item 7.3 applies to any outdoor air inlet connected to a ducted return of the dwelling unit HVAC system, regardless of its intended purpose (e.g., for ventilation air, make-up air, combustion air). This Item does not apply to HVAC systems without a ducted return.

    Footnote 48) For an attached dwelling unit, excluding units in dwellings (i.e., duplex) and townhomes, the override control is not required to be readily accessible to the occupant. However, in such cases, EPA recommends but does not require that the control be readily accessible to others (e.g., building maintenance staff) in lieu of the occupant.

    Please see the ENERGY STAR Single-Family New 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)

    Continuously operating ventilation and exhaust fan controls are not specifically addressed in the 2009 IECC.

    201220152018, and 2021 IECC

    Section R403.6 (R403.5 in 2012 IRC) Mechanical ventilation (Mandatory).  Building ventilation must meet the requirements of the International Residential Code or International Mechanical Code, as applicable, or have another approved means of ventilation. 

    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, 2012, 20152018, and 2021 International Residential Code (IRC)

    Continuously operating ventilation and exhaust fan controls are not specifically addressed in the IRC.

    Existing Homes

    SCOPE

    If any exhaust fans currently exhaust into the attic, crawlspace, between floors, or into any other part of the home, replace the duct with one that exhausts to the outside. If the project will involve working in the attic, see the assessment guide, Pre-Retrofit Assessment of Attics, Ceilings, and Roofs.

    For more on exhaust fan ventilation, see the U.S. Department of Energy’s Standard Work Specifications.

    See the Scope tab for additional job specifications.

    DESCRIPTION

    If the home currently has no whole-house ventilation system, such as a heat recovery ventilator (HRV), energy recovery ventilator (ERV), or fresh air intake ducted to the central air handler fan, then code-required ventilation can be provided with an exhaust fan that is set to run either continuously or for timered intervals. If a new exhaust fan is installed and set for continuous operation, or if an existing fan is set for continuous operation, the override controls to turn off the exhaust fan if necessary should be clearly marked, as described in the Description tab.

    COMPLIANCE

    See Compliance tab. 

    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*
    *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

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    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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