Green BuildingIndexLEED Guides and AnalysisSustainability

Guide to ASHRAE 62.1-2007 and Natural Ventilation for LEED 2009


  • The following notes are based on:
    • LEED 2009
    • The ASHRAE 62.1-2007 Standard
    • Credit Interpretation Rulings from the USGBC
    • Review comments on previously reviewed LEED projects
    • Direct conversations with USGBC reviewers regarding projects pursuing LEED certification
  • The USGBC references ASHRAE 62.1-2007 for compliance with Indoor Environmental Quality Pre-requisite 1 (IEQ p1). In other words, demonstrating compliance with ASRHAE 62.1-2007 is a requirement.
  • It is the Engineer of Record’s responsibility to confirm and demonstrate compliance with ASHRAE 62.1-2007
  • There are two major sections in ASHRAE 62.1
    • Section 5: Natural Ventilation
    • Section 6: Mechanical Ventilation


  • Covered in Section 5 of ASHRAE 62.1-2007.
  • Applies to all occupiable spaces.
  • Entry vestibules and kitchen cabinets do not need to be included in the 25’.
  • Kitchens do need to demonstrate compliance with Natural Ventilation (or if not possible, mechanical ventilation).
  • Windows must have operable opening area of 4% of floor area or more.
  • Occupied areas need to be within 25’ of the operable windows.
  • Ventilation through an adjoining room is acceptable IF:
    • The opening is at least 8% of the room area and not less than 25 SF.
    • AND the adjoining room is within 25’ of the operable windows. This is a point that is often confused. The adjoining room cannot be further than 25’ from the windows.
  • There is an alternative compliance path where a local code official can approve an engineered natural ventilation system. However, this is only acceptable if local code is the same as or references ASHRAE 62.1-2007. Florida building codes does not do this, so this path is not applicable to Florida.
  • If the entire dwelling unit is not complying with Natural Ventilation under Section 5, then Section 6 needs to be applied.
  • If complying under Section 5, Natural Ventilation, then Section 6 is not applicable.


  • Note that kitchen exhaust is a requirement under Section 6. As noted above, if the unit is naturally ventilated, then only Section 5 applies. Therefore, a recirculating range hood with no additional kitchen exhaust is acceptable IF the unit can be shown to be meeting all of the criteria for Natural Ventilation.
  • If the unit is NOT complying with the Natural Ventilation criteria, then kitchen exhaust needs to be examined closely. If mechanical ventilation is being introduced, then the project may then fall under Section 6 of ASHRAE 62.1-2007 which has minimum criteria for kitchen exhaust.
  • Note that kitchen exhaust can be way to comply with ASRHAE 62.1 ventilation. In other words you may be able to introduce continuous kitchen exhaust, which would bring the kitchen space in compliance with ASHRAE 62.1.


  • If the project is pursuing mechanical ventilation, the requirements under Section 6 apply.
  • Per note above, this includes Exhaust requirements.


  • LEED Reference Guide
  • LEED User ( This is a forum based help website for LEED. There are great resources on here organized by credit. There are also numerous help / answer questions for each credit. There is a good chance someone has already asked a question you may have, and others have offered advice.
  • ASHRAE 62.1-2007 document
  • ASHRAE 62.1-2007 User’s Manual
  • USGBC Credit Interpretation Rulings Database (