HVAC Systems

Some descriptions/characteristics of my HVAC system:

• I started with creating spaces in my building and assigning one space per HVAC zone. There are 27 spaces/zones in total, ranging from very small ones such as mechanical rooms to very large ones such as entire exhibition halls/lobbies combined open spaces.
• Next, I created a space schedule and adjusted the number of people in each space using the area per person property for each space type.
• I then made an HVAC loads report to better understand what loads are most significant in each zone.
• I tried making the annual building energy report, but it was taking too much time, so I used the provided formula to find approximate required supply airflow for each space/zone.
• Based on that airflow, I added a number of supply air terminals (supply diffuser 24x24 face 12x12 connection) in each space to match (or slightly exceed) the CFM requirements. These were placed at the same height as ceilings.
• I used air-based systems for ventilation, heating, and cooling. First I installed an air handling unit (vertical packaged DX 6 tons 4000 CFM) in mechanical rooms on each floor. I realize now that these mechanical rooms are too small to host these units so something I would need to change in my architectural model is the size of these rooms. I would like to keep air handlers within these rooms on the inside of the building.
• I then added all the supply ducts, and connected them to the air handlers and terminals. At this stage, my simplified model does not include return ducts or return air terminals, but I would model them in the same way as the supply ones, making sure I avoid any conflicts between the two types of ducts.
• I used rectangular ducts with radius elbows/tees. I started with the same size for all ducts (12”x12”) and then I used automatic sizing to change the size of the ducts. This worked mostly fine but there were some parts of the duct system that could not be automatically sized. Revit gave several warnings. In some cases there was not enough space to increase duct size, and sometimes connections between ducts were not working. In those cases, I at least tried to size subsets of ducts covering related zones. I restricted duct size to 24”x24” to make sure they can fit in the space above ceilings. I also used many flex round ducts to connect ducts and terminals.
• Ducts are placed above ceilings and below floors above, as can be seen in my architectural model. There are no major clashes with structural elements, except for structural walls as ducts go through them. There is still some work left in the architectural model regarding editing this above-ceiling space to make sure it’s not visible from the outside. I adjusted the height of the interior walls to avoid clashing with ducts.
• Finally, I added VAV units (single duct 12”) between ducts and air terminals in each zone. This lets people control temperature separately in each zone, and increases occupant comfort.
• I tried to add louvers/grilles to the exterior walls of mechanical rooms but I had trouble finding them in Revit. Another thing to be added in a more detailed model.
• I am aware of the many limitations and simplifications of this model, but I certainly learned a lot and I am confident in the work I’ve done so far. The remaining aspects would be added in a similar way, making sure that sizing and location of all HVAC system elements are fine.