Dear,
there is indeed a difference, there are actually a lot of differences ...
- wind load is different as function of height, thus are convective heat losses
-
transmission losses depend on external surface area, so the lowest and highest flat will have different values there
Besides that, a cooling load is strongly determined by internal heat gains and solar radiation. So, in case the solar exposure between south and west (at building and float level) differs, as do the internal gains, you have to subdivide into multiple zones. Furthermore, comfort temperatures are zone dependent... so you will probably want to make a difference on that as well.
The question on how to model the elevator is more difficult to answer. It depends on what you need to know from it. If the common areas are not cooled, it might be OK to treat them as a single zone. Check whether a temperature difference of a few degrees in the common areas makes a difference on the cooling load within the flats or not ...
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