Continuously Operating Ventilation and Exhaust Fans
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 Certified 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.
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.
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.
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ENERGY STAR Certified Homes (Version 3/3.1, Revision 08), Rater Field Checklist
7. Whole-House Mechanical Ventilation System
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 standalone wall switch, but not for a switch that’s on the ventilation equipment).
ENERGY STAR Revision 08 requirements are required for homes permitted starting 07/01/2016.
Exhibit 1: Mandatory Requirements. Certified under ENERGY STAR Qualified Homes Version 3.
Continuously operating ventilation and exhaust fan controls are not specifically addressed in the 2009 IECC.
Continuously operating ventilation and exhaust fan controls are not specifically addressed in the 2009 IRC.
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.
Continuously operating ventilation and exhaust fan controls are not specifically addressed in the 2012 IRC.
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High-Efficiency Fans = High-Efficiency Fans