Overall HVAC System Strategy:
Overall HVAC system design:
Three key points of my overall HVAC system design strategy:
- Load reduction: maximize the use of natural ventilation and passive heating/cooling strategies while making sure the air supply is adequate.
- Proper sizing: Proper size of the equipment and duct systems is another important factor in my HVAC design. Oversized systems may lead to inefficient operation.
- Zoning: Divide my building into different zones and provide individual control over heating and cooling in each zone through a VAV unit. This allows occupants to adjust the temperature to their liking, which can lead to energy savings and increased comfort.
To achieve this, multiple HVAC strategies are used and will explain below. Firstly, I set up space and HVAC zones in a new mechanical model for my building based on the rooms and space I created in my architectural model. After setting the space, I changed some of the floor areas per person assumptions set for each space type to achieve more accurate peak occupancy estimates. For example, I changed the area per person for the classroom to 50 SF. Also, for the two conference rooms, I changed one of them to be a large conference room which has an area per person of 60 SF (capacity of 15 people), and the other one has an area per person of 150 SF (capacity of 6 people). I set the condition type of mechanical rooms, stairs, and storage room to be unconditioned. Finally, I ran the HVAC Loads Analysis and Annual Building Energy Simulation,
The space schedule pictured below shows the results. I needed to make some adjustments because the Annual Building Energy Simulation combined certain zones in its analysis. To supplement this, I calculated an approximately required supply airflow using the formula provided to us (as seen in column J). The supply airflow was used to determine the number and airflow capacity of the air terminals needed for each zone.
Because my mechanical rooms are designed for one per level, I decided to have an air handler on each floor. I prefer having three smaller air handlers on each floor as opposed to one large air handler on the roof because I want to maximize the usable roof space for the solar panels and green roofs. My mechanical rooms are also all centrally located on their respective floors, which was done to minimize the distance the ducts needed to travel to reach each necessary space. The supply ducts have a middle elevation of 13’ and the return ducts are below the supply ducts and have a middle elevation of 11’6’’. Also, I designed my ducts to generally have wider than taller in order to minimize the amount of ceiling height that would be lost with taller ducts (but it changes my dimension when I used the auto-sizing feature).
Cross-section view:
Level 1:
Level 2:
Level 3:
The architectural, structural, and mechanical models were uploaded and merged together in the Autodesk Cloud.
Level 1 Exhibit:
Level 1 corridor:
Level 2 corridor:
Level 2 exhibit:
Level 3 exhibit:
Level 3 corridor:
Heating and Cooling Strategy
The analysis I ran on my building indicated that I would need to focus more on the cooling side rather than heating. Considering the purpose of a large building area like this, it's reasonable to expect that a large influx of people visiting exhibits, dining in the cafe, and using the offices and conference rooms would generate additional heat, in addition to the existing heat from the environment.
As ventilation via air transportation is likely necessary, I decided to utilize the same system for my heating and cooling needs to maintain simplicity in design and construction. I also used VAV units in my HVAC systems to control the temperature and airflow to different zones within a building to provide more precise temperature control and energy efficiency.
Apart from the air transport system, I incorporated passive solar strategies in the initial phases of my building's design to provide its heating and cooling. This entailed the use of suitable overhangs and light shelves for the curtain wall, which minimize solar heat gain during the hot summer months and maximize it during the colder winter months. Additionally, the high thermal mass values of the exterior walls, precast concrete floor slab, and green roofs will help regulate indoor temperatures.
Challenges:
One challenge I am having is with the sizing of the ducts. I am getting an error about some flow in the section is 0, but I am pretty sure the ducts are connected because I can see it changes the shape. I only did duct resizing for part of my HVAC system.