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855773520-LEED-v5-ID-C-Reference-Guide-Launch-Edition-1 - Page 321

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INCREASED VENTILATION THRESHOLDS

Projects must demonstrate a 15% increase in outdoor airflow rates over the minimum requirements of ASHRAE Standard 62.1-2022 . Most large HVAC systems can accommodate a 15% increase with minimal impacts to the design and to energy consumption. An alternative threshold of 30% is available through exemplary performance.

REGULARLY OCCUPIED SPACES REQUIREMENT

At least 95% of all regularly occupied spaces must have increased ventilation. This provides flexibility for projects that cannot meet the higher thresholds in every space.

DETERMINING THE INCREASED VENTILATION REQUIREMENT

The following VRP calculations determine the increased ventilation requirement:

  • Single-zone or 100% outdoor air system . Multiply the calculated minimum outdoor air flow for the system (Vot) by 1.15.

  • Multiple-zone recirculating system . Multiply the uncorrected outdoor air flow for the system (Vou) by 1.15. Multiply the breathing zone outdoor airflow for the critical zone (Vbz for critical zone) by 1.15. Calculate the new system ventilation efficiency (Ev) using the updated values for Vou and the critical zone Vbz and recalculate the required outdoor air intake flow for the system (Vot) using these values.

Option 2. Enhanced IAQ Design

The option requires using more stringent design limits for ozone, formaldehyde and PM2.5 to achieve enhanced levels of IAQ beyond EQp2: Fundamental Air Quality. This credit uses LEEDspecific design targets, selected by the LEED indoor EQ technical advisory group, with the following basis:

OZONE

A design target of 10 ppb was selected as referenced in the Environmental Health Committee (EHC) Emerging Issue Report [117] . This number reflects the thinking that ozone indoors is harmful and the lower the concentration, the better. Studies indicate that any “safe” threshold would exist at very low concentrations.

117 “Emerging issue: Ozone and indoor air chemistry”, ASHRAE, (2011), accessed March 31, 2025, https://ashrae.org/file%20library/communities/committees/standing%20committees/environmental%20health%20committee%20(ehc )/ehc_emerging_issue-ozoneandindoorairchemistry.pdf.

U.S. Green Building Council LEED v5 Reference Guide for Interior Design and Construction, April 2025 Launch Edition 310

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