HVAC Systems

Your Name
Sage Crosby
Linked Student
Journal Entry For
Module 9 - HVAC Systems
Mar 2, 2022 7:25 AM
Last Edited
Mar 4, 2022 4:51 PM

I began this module by setting up HVAC zones in a new mechanical model for my building based on the spaces I created in my architectural model. After setting the space type for each space, I played around with and changed some of the floor area per person assumptions set for each space type to achieve more accurate peak occupancy estimates. For the lobby I increased it from 7.18 to 20 sf/person, from 16.56 to 20 sf for the classrooms, and from 26.91 to 35 sf for the exhibition spaces. I had some trouble finding appropriate space types for some of my rooms like the kid zone, cafe seating area, and elevators, so I left these as the default <building> space type.

Using the HVAC zones, I ran the annual building energy and HVAC loads analyses. The space schedule pictured below contains some of the results of my estimates and results from the HVAC load and sizing analysis (i.e. the specified supply airflow for each zone). The supply airflow was used to determine the number and airflow capacity of the air terminals needed for each zone. One challenge indicating a potential modeling error is that the HVAC load analysis did not calculate a supply air flow for every zone.


I also created an analytical spaces schedule to summarize the results of the annual building energy report. In the schedule (below), I included the annual peak heating, peak cooling, lighting, power, and occupancy loads.


For my HVAC system, I decided to go with an air system for both heating and cooling. Since I made my floor height quite tall (13’), I have stacked the supply and return ducts on top of each other. I have chosen to put the air handling unit on the roof to avoid taking up more space on each floor.

This is the layout of the return/supply ducts and air terminals for the 3rd (top) floor of my building:


One challenge I am having is with the sizing of the ducts. I am getting an error about the connections being invalid due to the duct being modified to be in the opposite direction. Since I cannot run the duct sizing tool, I am unsure if I will need to provide more space between the supply and return air ducts, although I currently have them placed so that the top of the return ducts are 1 foot below the bottom of the supply ducts to account for significant resizing needs.