This prerequisite establishes a baseline for providing a minimum amount of outdoor air to buildings in order to maintain good indoor air quality and keep occupants comfortable and healthy. 

The referenced standard is ASHRAE 62.1-2016, which is a newer version than that referenced in LEED v4. ASHRAE 62.1-2016 is often more stringent than local building codes.

The prerequisite has different compliance paths for mechanically ventilated and naturally ventilated spaces, and you may need to follow both paths for the same building on a space-by-space basis. In fact, teams should beware that ASHRAE 62.1-2016 effectively prohibits natural ventilation via operable openings as a stand-alone strategy. This is because the standard requires spaces to be mechanically ventilated whenever the operable windows are closed. Multifamily residential buildings may be most impacted by this type of scenario.

What’s New in LEED v4.1

• The prerequisite now references ASHRAE Standard 62.1 version 2016.
• Outdoor air monitoring requirements are now more specific; this goes for both mechanically and naturally ventilated spaces.
• ISO requirements, instead of the CEN standard, are now allowed for demonstrating achievement—but this alternative applies to non-U.S. projects only.
• Specific sections of ASHRAE 62.1 that must be followed have been updated.
• The requirement for Healthcare has been updated to ASHRAE Standard 170-2017, Sections 6-10.
• Residential units must meet the requirements of two LEED v4.1 Multifamily prerequisites: EQ Prerequisite Combustion vending, and EQ Prerequisite Radon-resistant construction.

Should I upgrade?

The biggest change here is the update to the 2016 version of the ASHRAE, but the standard is not drastically different or more stringent than previous versions. Unless your project has a specific characteristic more suited to the 2010 version of ASHRAE, we recommend upgrading to reflect the more current standard for high-quality indoor environments.