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Baseline for outdoor air ventilation

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 62.1-2010, which is a newer version than that referenced in LEED 2009. ASHRAE 62.1-2010 is often more stringent than local building codes, although it is not likely to entail any added costs.

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 62.1-2010 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

  • The prerequisite now references ASHRAE Standard 62.1 version 2010.
  • Window configuration and ceiling height are now considered in ASHRAE 62.1-2010 natural ventilation calculations.
  • Supplementary mechanical ventilation systems for naturally ventilated spaces are required by ASHRAE 62.1-2010 in some cases.
  • USGBC requires project teams to confirm the appropriate use of natural ventilation through the flow chart in CIBSE AM10, Figure 2.8.
  • CEN requirements, instead of ASHRAE 62.1-2010, are now allowed for demonstrating achievement.
  • EQc1: Outdoor Air Delivery Monitoring is now included in this prerequisite. Additionally, USGBC distinguishes between variable air volume and constant volume systems in its monitoring requirements.
  • LEED now includes specific requirements for residential projects for this prerequisite, which were largely taken from LEED for Homes EQc2, Combustion Venting.