855773644-LEED-v5-BD-C-Reference-Guide-Launch-Edition - Page 489

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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 Indoor Air Quality 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 environmental quality 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. This number reflects the thinking that ozone indoors is harmful and lower the concentration the better. Studies indicate that any safe threshold would exist at very low concentrations. [155]

FORMALDEHYDE

A design target of 20 µg/m³ (16 ppb) was selected based on the NIOSH recommended airborne exposure limit (REL) and FEMA goal for emergency housing [156] . Formaldehyde is a carcinogen that can irritate the skin and eyes. [157] Long-term exposure has been associated with increased allergic sensitivity and asthma. Many building products contain formaldehyde as addressed in the MRc3: Low-Emitting Materials .

155 “Emerging issue: Ozone and indoor air chemistry”, ASHRAE, (2011), https://www.ashrae.org/file%20library/communities/committees/standing%20committees/environmental%20health%20committee%2 0(ehc)/ehc_emerging_issue-ozoneandindoorairchemistry.pdf. 156 “Formaldehyde — A Common Air Pollutant”, Chemical Insights, (2021), https://chemicalinsights.org/wpcontent/uploads/FactSheet_Formaldehyde.pdf.

U.S. Green Building Council LEED v5 Reference Guide for Building Design and Construction, April 2025 Launch Edition 479