Glenn KatzThe building is in NYC and the site sunlight majorly comes from the southern side.
Winter months (Dec-Mar) show highest temperature of 48F and can go as low as 28F.
Summer months (Jun-Sep) show lowest temperature at 61F and can go as high as 85F.
For spring and fall the transitional temperature is in the moderate range.
Design Inspirations
My goal was to create an HVAC system that not only is simple and efficient but also compliments the architectural and structural designs.
I wish to incorporate the natural ventilation in living beings that can efficiently regulate temperature and airflow without overloading the system.
I will use smart cutting edge tech like smart thermostats, IoT sensors, building automation systems to optimize the energy usage and user comfort from the HVAC system and the whole building in general.
Variable Refrigerant Flow (VRF) systems: I plan to have variable cooling/heating in different zones/sub-zones of the building which offers flexibility and energy savings.
I will use the return air to precondition the incoming fresh air, which would help reducing energy consumption and improve the indoor air quality.
OVERALL HVAC DESIGN STRATEGY
Target for my HVAC system: optimal occupant comfort, energy efficiency and sustainability.
I have used the building orientation and site conditions to create passive measures to minimize the need for HVAC systems. I have used R-60 roof, R-38 exterior walls to provide excellent insulation. I have provided curtain wall with overhand that prevents direct sunlight in summer but allows in winters, which helps keep the building cold in summers and hot in winters. I have put 3 big skylight for my atriums that allow sufficient sunlight but prevents excess heat.
For my HVAC system I will use dynamic system that has adaptive cooling and heating setpoints for each zone that ensures flexibility with respect to varying weather conditions and increase energy efficiency.
I have divided my building into different zones and the HVAC system takes the solar exposure and intended use of rooms in the zones into account. Further, the different zones would have separate advanced measuring systems in place to minimize energy usage/loss.
Implementation Steps
Step 1: Assigning HVAC Zones
For each floor, I have divided the rooms into three HVAC zones based on combination of intended usage, solar exposure. Each floor has a separate utility (mechanical) room that has Air Handler Units placed in it for each zone on the floor.
Zone 1 - SE
This is the area that would have major solar exposure and will have frequently occupied spaces. It primarily consists of education spaces, conference rooms and offices. It also has one of the two cafe spaces that makes the building a vibrant and inviting space for everyone.
Zone 2 - Central
This is the core area of the building and serves as a central hub for the entire building. It mainly consists of the exhibition spaces, hallways, play room and the gift shop. It also has the other cafe space that overlooks an amazing space outside, which will be used to provide a thrilling dining experience.
Zone 3 - NW
This is the area that would have least solar exposure and will have least frequently occupied spaces. It primarily consists of restrooms, elevators and staircase.
Step 2: Heating and Cooling Strategy
Zone 1 - SE: Due to the low temperatures and excessive cold winds we need a higher heating air temperature (95F) and the heating setpoint is chosen to be 70F to provide comfortable environment.
Zone 2 - Central: As the core area that consists of mainly exhibition spaces and hallways, moderate heating air temperature of 85F is set and the heating setpoint is chosen to be 70F to balance the comfort in the building.
Zone 3 - NW: Due to the low temperatures and excessive cold winds we need a higher heating air temperature (90F) and the heating setpoint is chosen to be 70F to provide comfortable environment.
Zone 1 - SE: Due to high solar exposure we need a lower cooling air temperature (55F) and the cooling setpoint is chosen to be 75F to combat the increase in temperature.
Zone 2 - Central: As the core area that consists of mainly exhibition spaces and hallways, moderate cooling air temperature of 60F is set and the cooling setpoint is chosen to be 75F to balance the comfort in the building.
Zone 3 - NW: Due to the moderate solar exposure we need cooling air temperature as 58F and the cooling setpoint is chosen to be 75F to provide comfortable environment.
In Summary: To provide maximum comfort the cooling and heating setpoint are the same throughout the building.
Zone 1 - SE:
- Cooling Air Temperature (Supply Air): 55°F.
- Cooling Setpoint: 75°F.
- Heating Air Temperature (Supply Air): 95°F.
- Heating Setpoint: 70°F.
Zone 2 - Central:
- Cooling Air Temperature (Supply Air): 60°F.
- Cooling Setpoint: 75°F.
- Heating Air Temperature (Supply Air): 85°F.
- Heating Setpoint: 70°F.
Zone 3 - NW:
- Cooling Air Temperature (Supply Air): 58°F.
- Cooling Setpoint: 75°F.
- Heating Air Temperature (Supply Air): 90°F.
- Heating Setpoint: 70°F.
Step 3: HVAC Zones and Load Reports
HVAC Zones with Peak loads and Airflow
Default Spaces:
Zone Name | Peak Cooling Load (Btu/h) | Peak Cooling Airflow (CFM) | Peak Heating Load (Btu/h) | Peak Heating Airflow (CFM) | Peak Ventilation Airflow (CFM) |
Default | 39,208 | 1,069 | 23,309 | 391 | 185 |
Central Zones:
Zone Name | Peak Cooling Load (Btu/h) | Peak Cooling Airflow (CFM) | Peak Heating Load (Btu/h) | Peak Heating Airflow (CFM) | Peak Ventilation Airflow (CFM) |
Level 1 - Central | 163,294 | 4,520 | 94,915 | 1,435 | 1,435 |
Level 2 - Central | 106,194 | 4,100 | 46,818 | 572 | 572 |
Level 3 - Central | 106,517 | 4,038 | 47,551 | 590 | 590 |
Level 4 - Central | 137,168 | 4,475 | 78,440 | 1,162 | 1,057 |
NW Zones:
Zone Name | Peak Cooling Load (Btu/h) | Peak Cooling Airflow (CFM) | Peak Heating Load (Btu/h) | Peak Heating Airflow (CFM) | Peak Ventilation Airflow (CFM) |
Level 1 - NW | 32,154 | 793 | 20,427 | 384 | 179 |
Level 2 - NW | 19,185 | 526 | 6,642 | 79 | 75 |
Level 3 - NW | 19,185 | 526 | 6,642 | 79 | 75 |
Level 4 - NW | 12,940 | 388 | 6,929 | 83 | 80 |
SE Zones:
Zone Name | Peak Cooling Load (Btu/h) | Peak Cooling Airflow (CFM) | Peak Heating Load (Btu/h) | Peak Heating Airflow (CFM) | Peak Ventilation Airflow (CFM) |
Level 1 - SE | 86,675 | 1,363 | 68,094 | 978 | 978 |
Level 2 - SE | 147,504 | 5,222 | 59,192 | 776 | 691 |
Level 3 - SE | 124,616 | 4,882 | 37,199 | 549 | 358 |
Level 4 - SE | 145,208 | 5,148 | 57,956 | 743 | 672 |
Summary
Zone Name | Minimum Volume of Downstream Air Required | Air Handling unit Employed | Required Cross-Section Area | Selected Rectangular Duct Cross-Sections |
Level 1 - Central | 4,520 | 5,000 CFM | 5 SF | 24x24 |
Level 2 - Central | 4,100 | 5,000 CFM | 5 SF | 24x24 |
Level 3 - Central | 4,038 | 5,000 CFM | 5 SF | 24x24 |
Level 4 - Central | 4,475 | 5,000 CFM | 5 SF | 24x24 |
Level 1 - NW | 793 | 1,000 CFM | 1 SF | 12x12 |
Level 2 - NW | 526 | 1,000 CFM | 1 SF | 12x12 |
Level 3 - NW | 526 | 1,000 CFM | 1 SF | 12x12 |
Level 4 - NW | 388 | 500 CFM | 0.5 SF | 9x9 |
Level 1 - SE | 1,363 | 2,000 CFM | 2 SF | 12x24 |
Level 2 - SE | 5,222 | 6,000 CFM | 6 SF | 24x36 |
Level 3 - SE | 4,882 | 5,000 CFM | 5 SF | 24x24 |
Level 4 - SE | 5,148 | 6,000 CFM | 6 SF | 24x24 |
Step 4: Design Ducts, Air Terminals, Air Handlers
Elevation Views:
Level 1:
Level 2:
Level 3:
Level 4:
3D View:
Step 5: Model Coordination in ACC
HVAC Challenges
My first challenge was dividing the building into zones. I have used the solar analysis and room/space usage to divide the building into 3 zones per floor.
One of the biggest challenges I faced was making sure that supply and return ducts do not clash with each other or with structural system. Working in Revit, I have tried to adjust the ducts as much as possible. I have started with measuring the distance between floor and beams and used that to adjust the top level of ducts.
Another challenge I faced was for some rooms/spaces I needed many dispensers (due to exceptionally high airflow requirement) but did not have the space, for those spaces I plan to adjust the envelop to reduce the airflow requirements. For now i have tried to solve it by increasing the airflow of each dispenser. I believe the cause is the big curtain wall that allows large quantity of heat intake.
I have not adjusted the duct sizes due to improper connection between ducts and air terminals at some places due to which duct sizes are not very accurate.
