Hello, I have a site that has a shared OAD for two units. The duct is not large enough to supply the minimum OA, and one of the spaces have changed usage. Even with reduced CFM per occupant based on units that can't meet the minimum we are still short. Replacing the units and inlarging the ductwork is not an option. Will this cause the section to fail? Are there any suggestions on what can be done?
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Dave Hubka
Practice Leader - SustainabilityEUA
LEEDuser Expert
495 thumbs up
February 24, 2024 - 8:14 pm
The v4 language allows a path when 62.1 vent rates cannot be met..."If meeting the outdoor airflow rates in Case 1 is not feasible because of the physical constraints of the existing ventilation system, complete an engineering assessment of the system’s maximum outdoor air delivery rate. Supply the maximum possible to reach the minimum setpoint in Case 1 and not less than 10 cubic feet per minute (5 liters per second) of outdoor air per person."
The LEED v5 Existing Building reference guide draft states "Compliance with minimum outdoor rates is highly encouraged but not required for this prerequisite." I wonder if you could wait and submit this project through v5 once it becomes available?
Otherwise run the project through v4 if you can provide at least 10 cfm of outdoor air per person.
Hope this helps!