Images
Building 1 3D HVAC Layout
Building 2 3D HVAC Layout
Building 3 3D HVAC Layout
Building 1 Floor 1 HVAC
Building 1 Floor 2 HVAC
Building 2 Floor 1 HVAC
Building 2 Floor 2 HVAC
Building 3 Floor 1HVAC
Building 3 Floor 2 HVAC
Building 1 AHU Closeup
Overall HVAC System Strategy
Temperature comfort and control have been a design consideration from the very start of the design. As you can see from the floor plans and 3D views, there is a Foyer at the main entrance, another one at the entrance to the second floor patio, and the hallways connecting each building have walls and doors to keep them enclosed. Each of these ingress and egress locations is carefully contained within itself. If someone walks into the main entry foyer, they are not exposing the large lobby to the exterior elements. If a family comes in from lunch on the patio, they are not letting the air conditioning leave the cafeteria into the summer sun. If a class comes in from an interactive experience in the natural environment between all three buildings, they are then housed in an intermediate hallway, rather than an exhibit or lobby, letting all the heat for the main spaces flow out the door. Each main entry and exit point that will be frequently used has this in order for the larger, more populated spaces, to use less energy frequently reheating or cooling a space.
The energy model doesn’t completely represent the system well, as I had a few different motives for separating the spaces to different AHUs. First and most importantly, the different buildings have different uses, as outlined in my bubble diagram from earlier planning, so the heating and cooling controls will likely need to be adjustable locally. Also, Buildings 2 and 3 (Southwest and southeast, respectively) are a bit “disconnected” from the main building (Building 1, the large, northernmost building). With this length of distance away from the main building and mechanical room, as well as the anticipated demand for each space, I decided to use different AHU’s for simpler coordination between the architecture and the structural design, as smaller ducts can be used with smaller zones to cover.
This can also come in handy if there is an “off-season” or if there is ever maintenance needed. If one exhibit space, or the meeting rooms won’t be used, those can be less temperature controlled for a time without impacting the other systems downstream. I had Building 2 (SW direction, with just the conference room and exhibit on each floor) in mind with this, as the office spaces and classrooms in Building 3 can be reached without going through 2, and the heating and cooling load for the entire property can be reduced if Building 2 is shut off or put in standby mode.
My strategy with the air system setup themselves was to use the natural density of air at different temperatures to maximize the effectiveness of the system required. As stated below with the Heating and Cooling strategy breakdowns, I used a lot of passive heating and cooling techniques for this space the ensure a massive air system would not be needed for temperature control. Air turnover and ventilation will be needed of course, though, and I used the Systems Analysis to see which load would require more help with an air handler. As shown in the peak load table, cooling with the air handling system will be required more in these buildings. With this in mind, and taking advantage of the greater density of cold air, my supply air terminals are placed on the top of the spaces, and my returns are at the floor level. This allowing the cold air to fall on all people in the space as it stratifies below the warmer air already present, and would require less work for the system in place.
Terminal sizing is based off the calculated CFM needed for each space, I chose the greater of the 2, which was usually cooling.
All spaces were provided with the proper amount of supply and return terminals, as shown in the table below.
As shown in the 3D images above, as well as with the lack of ductwork shown on the Floor 2 plans, all return air traveled through ducts at the ceiling level of the first floor. Most of the terminals (except for a select few where space would not allow) were mounted directly on the ducts right in the walls. This allowed for easier routing to the second floor, as I was able to connect to the original ductwork but just fish it up through a wall on the level above. As a general idea, my supply ducts are near the windows, while my returns are near the inside/middle of the rooms.
These images show the second floor Return Air vent (cross section and plan view):
Heating Strategy
From an overall building design perspective, there was a greater need for heating to provide comfort based on this location in New Jersey, as the psychrometric chart shows. To combat this, I used very well insulated walls, glazings, and floors to help retain heat. I used a lot of large windows on the south side of the building (below the roof overhang) to ensure the winter sunlight could get in and help heat the space naturally, and kept the windows on the back side of each building (the north side) smaller to allow for less heat to be lost there.
Cooling Strategy
To cool my building cluster passively, I mostly used my roof. First, all around the building has a 3’ overhang to block the summer sun from beaming too directly into the rooms. Certain windows also have shades on them, like the 96”x60”x14” Window-Bay-Casement windows used on the south side of Buildings 2 and 3. Also, the upper windows in Building 2 and the skylights in Building 1 are all operable, allowing hot air to rise and leave when needed, and shown in the picture below. For more effective cooling when the air system is used and the windows are closed, a similar premise is used, as described in the overall description above. My supply air terminals are placed on the top of the spaces, and my returns are at the floor level, allowing for the cold air to fall on all people in the space as it stratifies below the warmer air already present. Also, just with the presence of the green roof, the buildings will not absorb as much heat as a traditional roof, as the earth holds its temperature better. I originally chose this location because it is close to two ponds and could have used a system of extracting the coolth from that water, but they are both south of the site, opposite of the natural wind flow here and also on private properties.
Challenges
The HVAC system was a fun challenge to set up. At first, making sure my analytical spaces were closed was a bit frustrating, as my green roof, interior glazed ceiling, and other specialty items caused some issues with enclosing the spaces.
Also, some of my analytical spaces combined when creating the systems report, as there were openings to combine the conjoined spaces. This included my lobby and second floor overlooking hallway combining to my grand Stairway (highlights+blue star), as well as my first floor cafe area combining into my food prep space (highlight+red star). See images below of the combined called airflow plus the 3D view of the spaces.
Also, the actual implementation of the “within wall” terminals was extremely tedious with duct sizing and connecting, and fitting it within the walls (images above). I still think it’s worth it though for true quality air circulation. Fishing the HVAC around the beams was a little difficult at times but I did end up being successful in the end. Starting my levels 15’ apart was very helpful.
This image shows the supply line below the beam height:
Connecting to my AHU’s was a pain with all the duct sizing, and the space required for the connections was greater than anticipated. I definitely could have saved a lot of time if I was not so stubborn about keeping my AHU inside of building 1 and off the roof, as well using the easier flex duct for the returns as well. As a result of the HVAC installation, I will need to make a couple simple enclosures for my Buildings 2 and 3 AHU’s, as well as shift the Mechanical room wall a bit. Otherwise, I should be all set to move forward.