Hello,
We are carrying out LEED certification of an office building. We have an atrium (similar to an indoor courtyard) in our building, which is mainly used as a corridor (passage) between adjacent buildings, although this atrium also serves as the entry and exit points of the offices in our building). We also have in the atrium a number of food court restaurants and a few stores. According to ASHRAE standard, if we assume this atrium as shopping center, the default number of occupants results in a very high number (since it assumes it’s a full scale shopping center), which in turn results in higher ventilation, cooling and heating requirements. Is it possible to reduce the number of people in this atrium space and make it exempt from ASHRAE standard’s default occupancy figures for retail spaces (maybe with a justified explanation by the designers)? After all, it’s not a shopping center and, therefore, it should not be designed as a shopping center.
Thanks in advance!
Jon Clifford
LEED-AP BD+CGREENSQUARE
LEEDuser Expert
327 thumbs up
November 2, 2014 - 2:05 pm
İlkyaz— I have been through this scenario before. ASHRAE 62.1-2007, Table 6-1, General Note 6, states, “If the occupancy category for a proposed space or zone is not listed, the requirements for the listed occupancy category that is most similar in terms of occupant density, activities and building construction shall be used.”
You have described an indoor atrium space that combines the functions of several Table-6.1 occupancies. It serves as a corridor between buildings, an office entry lobby or reception area, a public lobby, retail common area, and a cafeteria/fast food dining area. Our project had a similar, mixed-use, atrium/circulation space.
Since the food court area requires the highest ventilation (0.6 L/s/m2 & 3.8 L/s/person at 100 persons per 100m2), you may first have to justify NOT designing based on the most stringent requirement. Reviewers asked us to confirm that tenant agreements ensured that densely occupied dining areas could never expand beyond those shown on design drawings. They asked us to justify the lower occupancy rates assumed in non-dining, circulation areas and to defend our assumptions of peak usage patterns.
In our case, we found that “Retail Mall Common Area” WAS the most similar occupancy to our atrium. At 0.3 L/s/m2 & 3.8 L/s/person at 40 persons per 100m2, this category’s ventilation requirement lies about midway between those of “Fast Food Dining” and “Office Entry Lobbies.” Thus, it covers a range of uses, including circulation and dining, addressing broad fluctuations in traffic and activity. Unfortunately, it took us two appeals to justify our approach to the Review Team.
Your project may be able to justify even lower ventilation rates based on the Office Building “Reception Areas” or “Main Entry Lobbies,” but is it worth the risk? Minimum IAQ Performance is a Prerequisite. An unsuccessful justification could cost your project’s certification.
I would suggest outlining your justification in an inquiry to USGBC/GBCI. By asking for a formal, binding Interpretation in advance, you can design your systems appropriately from the onset.