One of my LEED v4 ID+C project getting below comments from LEED reviewer for Minimum Indoor Air Quality Performance Calculator (Project having AHU with VAV Boxes).
LEED Reviewer Comment:
Option 1: ASHRAE Standard 62.1-2010
1. For all the project spaces, the Ventilation Rate Procedure (VRP) calculation has been performed with values
for Zone Primary Air Fraction (Ep), however, the mechanical floor plan and schedules provided within Project
Information indicate that project spaces are served by VAV boxes (without secondary recirculation).
Therefore, for the project spaces, the Ep must not be considered in the VRP calculation.
Provide a narrative and update the VRP calcul ation as required. Additionally, note that in the Minimum IAQ
Performance Calculator, the zone discharge air flow (Vdz) and zone primary air flow (Vpz) for VAV boxes
without secondary recirculation are the same, and equal to the minimum airflow for the VAV box at the worst
case conditions. Ensure that all the parameters reported in the VRP calculation are actual and consistent with
the supporting documentation.
My Ques: We revise the Minimum Indoor Air Quality Performance Calculator as per below
Zone Discharge Airflow (Vdz),
Zone primary Airflow (Vpz) are same,
Zone Secondary Recirculation Fraction (Er) is 0 and Zone Primary Air Fraction (Ep) is 1
Is correct ? or Please Share other ways guys.
Dave Hubka
Practice Leader - SustainabilityEUA
LEEDuser Expert
525 thumbs up
September 19, 2023 - 8:26 am
for VAV boxes with no secondary recirculation:
Vdz = Vpz = lowest scheduled airflow at VAV box.
Er = 1.0
Ep is auto-calculated. (user does not select or enter value)
Nagaraj Sankar
1 thumbs up
September 19, 2023 - 11:53 pm
Thanks for your prompt response Mr. Dave Hubka.
Nagaraj Sankar
1 thumbs up
January 19, 2024 - 12:05 am
Hi @Davehubka ,
One of our another project having the same question as Preliminary review comment and clarification as well , I have attached Preliminary review comment and clarification raised by the reviewer team in below,
This Preliminary review comment comes in the project
It appears that the calculations may not have been performed for the worst-case conditions, as it is not clear if the cooling or heating condition calculations analyze the lowest supply airflow rate that can reasonably be expected to occur when each space is fully occupied. This lowest supply flow condition when occupied is anticipated to be the worst-case ventilation condition. For interior zones in cooling mode, this flowrate is expected to be somewhere in between the minimum flow setting and the design cooling flowrate. For the heating condition, this flowrate is generally expected to be the heating minimum flowrate.
This clarification occurs on the project after the preliminary review
1. (Preliminary Review Item #1) The response narrative provided indicates that the space was considered at worst-case conditions, but then states that sufficient documentation was not available and requests an exception. Confirm that the ventilation systems were considered at worst-case conditions and indicate the source of the system performance information utilized in the VRP calculations.
Please guide us to assist on this path, as well as guide as if we go to the case2 : System unable to meet the required airflows means what we need to submit
Dave Hubka
Practice Leader - SustainabilityEUA
LEEDuser Expert
525 thumbs up
January 19, 2024 - 7:48 am
If case 2 is pursued the team would need to complete an engineering assessment of the system's maximum outdoor air delivery rate AND demonstrate that the physical constraints of the existing ventilation system do not allow the system to meet the ASHRAE 62.1 ventilation rates during worst-case condition. Engineering Assessment / Physical Constraints can be difficult to demonstrate as acceptable to GBCI - in my past project experience. My recommendation is to continue to pursue Opt 1.
Without seeing your ventilation layout it is not possible to pinpoint the correct solution.
However, when coming across the GBCI comment provided above, the solution is typically "increase the scheduled supply air to the critical zone(s) until the system level can demonstrate compliance with 62.1".