Continuously Operating Ventilation and Exhaust Fans

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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. 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, Continuous Supply/Exhaust Fan Ratings, and Bathroom Ran 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.  Reference

  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.  Reference

  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.  Reference

    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.  Reference

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.

Scope

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

Ventilation Controls

Continuously operating ventilation and exhaust fans include readily accessible override controls:

  1. Install continuously operating ventilation and exhaust fans that have override control accessories.
  2. Install override controls for all fans in an easily accessible location.

Notes:

Override Control Location

It is important for HVAC contractors and electricians to locate the override controls for continuously operating ventilation and exhaust fans 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.

Override Control Location Recommendations:

Locate the labeled control near the thermostat, creating a control center for the homeowner. This allows 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.

Locate a switch on the electrical panel with a label. This prevents accidental turn off of fans and also provides one switch for all fans. This setup is ideal for a house that has multiple continuously running exhaust fans.

Some bath exhaust fans have internal override systems, either on the electrical switch plate or defined in the manufacturer’s manual. These exhaust fans meet the requirement as long as the override is accessible.

Training

Right and Wrong Images

Presentations

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Compliance

ENERGY STAR Version 3, (Rev. 07)

HVAC System Quality Checklist, Controls. Continuously-operating ventilation and exhaust fans include readily accessible override controls.

DOE Challenge Home

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

2009 IECC

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

2009 IRC

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

2012 IECC

Section R403.5 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. 

2012 IRC

Continuously operating ventilation and exhaust fan controls are not specifically addressed in the 2012 IRC.

More Info.

Case Studies

None Available

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).

Last Updated: 08/15/2013

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