# Modeling a full height atrium

Hi everyone,

I have a unique problem related to geometry and zoning that I'd appreciate some input on. I have a core and shell renovation of a mid-rise building (15-20 stories) which consists of offices with a full-height circular rotunda in the center. The rotunda is about 210 feet tall with a footprint on the ground floor of about 20,000 sqft, and is capped by a skylight which covers the entire projected area. I want to determine a zoning approach that will reasonably approximate the rotunda's thermal loads. Right now, the rotunda has no artificial lighting - outside of daylight hours, lighting will come from carryover from fixtures in the spaces around the perimeter. The building is in climate zone 5A.

Currently I've thought of two approaches: one is to model the rotunda as a single shell with a single floor. The ceiling would be the full height of the rotunda. The second approach would be to break up the rotunda into two or three vertical segments, each one a separate space and thermal zone. Which one of these approaches would most accurately capture the thermal loads on the rotunda (or is there a different approach I haven't thought of)? There's a few unique things to consider:

• The only exterior surface in the rotunda is the skylight at the top. The skylight looks closer to the transparent side of translucent, so I anticipate a fairly substantial amount of solar radiation entering the rotunda on sunny days. How far down would solar radiation "penetrate"? In other words, would the ground floor feel solar heat gain, or would the gain be concentrated in the upper levels?

• Given the height of the atrium, I also anticipate a lot of thermal stratification. Is that going significantly affect heat transfer to and from the adjacent office spaces (which will be maintained at standard temperature setpoints and have ceiling heights of about 11-12 feet)?

I'm using eQuest v3.64, but I'm sure this question is relevant to other software as well. (Side question: does DOE-2 explicitly model stratification effects, or does it assume a uniform temperature in a zone?

Thanks as always,

Drew Morrison

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