Although most buildings won’t have trouble meeting this prerequisite, there are some challenges that can sneak up unexpectedly if you don’t address it early.
The most important thing to confirm is that ventilation air is provided to all occupiable spaces in the building. This may seem obvious, but the prerequisite applies to areas that are sometimes overlooked, such as circulation, back of house spaces, and active storage rooms. Check out the EQ Overview section in the LEED v4 Reference Guide for a list of the space types that must be addressed.
Minimum Airflow Rates (for Mechanically Ventilated Spaces)
Teams can use the calculation provided in the O+M Guide to calculate the minimum amount of outdoor air that must be supplied. The calculation must be completed for each air handling unit (AHU) serving the project.
Alternatively, teams can determine minimum outdoor air rates using the Ventilation Rate Procedure outlined in Section 6.2 of ASHRAE 62.1 editions 2016, 2013, 2010, or 2007.
Once you’ve determined minimum outdoor air rates, you must take airflow measurements at each AHU to confirm that the minimum requirement is met. Remember to also verify that the results are within 10 percent of the rates outlined in your project’s Current Facilities Requirements and Operations and Maintenance Plan.
Goodbye, Case 2
A big change to this prerequisite is the removal of Case 2, which provided an alternative path to compliance for any system that could not meet required outdoor airflow rates due to physical or design constraints. Check out the guidance in the FAQs if your project is in this situation.
Natural Ventilation for Multifamily Residential
Multifamily projects can avoid the mechanical ventilation required by the ASHRAE standard by providing compliant operable windows in each residential unit bedroom.
Don’t Forget about Exhaust Systems
Teams must test and confirm that mechanical exhaust systems are operating properly. See the Documentation Toolkit for an example testing form that can be modified for your project.
What’s New in LEED v4.1
- Teams can calculate minimum outdoor air rates using the calculation provided in the O+M Guide.
- The referenced standard has been updated from ASHRAE 62.1-2010 to 62.1-2016 (however, note that the O+M Guide states that teams can choose to calculate minimum airflow rates using the Ventilation Rate Procedure outlined in Section 6.2 of ASHRAE 62.1 editions 2016, 2013, 2010, or 2007).
- Case 2 addressing systems that cannot meet required airflow rates has been removed.
- The minimum opening and size requirements for naturally ventilated spaces has been revised.
- The requirements for multifamily residential units have been clarified.
Should I upgrade?
LEED v4.1 gives teams more options for calculating minimum outdoor airflow rates than previous versions of LEED, which may be helpful to some projects.