I am modelling a small classroom that utilizes a double skin facade that preheats the outdoor air which then moves into the plenum(above suspended ceiling) and the inlet air is supplied to the room via diffuse ceiling ventilation. There is an exhaust inside the room so the whole ventilation principle is mechanically driven.

We want to calculate the energy balance in Energyplus but we are having issues with defining how the zones interact - and how the air moves from the cavity to the plenum and on to the occupied zone.

We have made mech. zone ventilation in the occupied zone as an exhaust, and natural zone ventilation in the cavity. We have also made zone mixing between cavity+plenum cavity, plenum cavity+plenum, and plenum+occ zone.

Does anyone have any advice on how to model the air flow path between the zones? And maybe any advice on how to model the diffuse ceiling?