Dears,
We are designing an enclosed Shopping Mall in Brazil, but have come to a halt when faced with the occupancy rates required by ASHRAE 62.1-2009. The mechanical team has considered four (5) separate AHU systems to each distinct area; retail stores, administration, bathrooms, cafeteria/fast food, and mall common areas.
For the last two areas, the occupant density required by ASHRAE is much higher than the rates demanded by the Brazilian norm for ventilation procedures NBR 16401.
To confirm the occupant density at cafeteria/ fast food areas, our team has gone to the extent of surveying a couple of existing malls at different times of the day and the final understanding was true to the local norm requirements.
At the Mall areas ASHRAE takes in consideration an occupant rate of 2,5 people per square meter (40 people / 100 m2) while our local norm dictates 8 people per square meter (12,5 p/ 100 m2). However, our local requirement for minimum air rate (cfm per person) is much higher!
If we simulate the final ventilation rate for 100m2 for instance, taking into consideration our occupant rates and raising air rates, we see that the volume of air per square meter can be met while still maintaining our local occupant rate norm:
Project in Brazil with minimum requirements
Mall – 17cfm x 12,50 person/ m2 (8m2/ person)= 100,29 L/s
Project in Brazil with raised air rate
Mall – 29cfm x 12,50 person/ m2 (8m2/ person)= 171,08 L/s
ASHRAE
Mall – 9cfm x 40 person/m2 (40m2/person)=169,90 L/s
Do you think by raising the air rate to meet the overall air volume per area will meet the intention of this credit?
Roger Chang
Principal, Energy and Engineering LeaderDLR Group | Westlake Reed Leskosky
LEEDuser Expert
398 thumbs up
January 11, 2011 - 1:11 pm
The default occupancies for ASHRAE 62.1 are good practice in the absence of more detailed data. I recommend also looking at ASHRAE 62.1-2007 and performing a calculation based on the sum of the people (5 cfm/sf min) and area based factors (0.06 cfm/sf min).