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.
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.
How to Locate the Override Controls
The installer has three options for locating the override controls:
- 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.
- 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.
- 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.
In homes with continuously operating ventilation and exhaust fans, the HERS rater should inspect to ensure that the fans include readily accessible override controls.
No climate specific information applies.
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.
National Rater Field Checklist
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.
Exhibit 1 Mandatory Requirements.
Exhibit 1, Item 1) Certified under the ENERGY STAR Qualified Homes Program or the ENERGY STAR Multifamily New Construction Program.
Continuously operating ventilation and exhaust fan controls are not specifically addressed in the 2009 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.
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.
Continuously operating ventilation and exhaust fan controls are not specifically addressed in the IRC.
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.
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.
See Compliance tab.
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