Yes, in locations where the local code does not require vestibules or revolving doors the project team may choose one of the two options below. Additionally, all projects using this method must provide a narrative explaining how infiltration and exfiltration of air through building entries is addressed in the design.
1. Manual subtraction of the energy cost savings associated with vestibules as conservatively estimated by PNNL-20026 “Energy Saving Impact of ASHRAE 90.1 Vestibule Requirements: Modeling of Air Infiltration through Door Openings”. Refer to the Related Resource “Default Deduction for Vestibules” for the specific percentage subtraction required based on project type and climate zone.
2. Provide detailed exceptional calculation method calculations with each step of the calculation clearly described and in alignment with the analysis performed in PNNL-20026, but specific to the project building. Document the additional energy consumption of the project building associated with removing the vestibules from the project. No credit will be given for the use of air curtains when using this approach. A sensitivity analysis related to the number of occupants entering on an hourly basis would need to be justified. The narrative would also need to justify that the simulation software is capable of addressing the conditions required for the calculation. (Software with a well-mixed air assumption would not be able to apply this modeling approach).
***Update 11/9/20: This ruling is now applicable to LEED v4.1 BD+C and ID+C projects.