4 units
Step 1 - Generative Design Framework
- Optimal design of office building
- Design Variables
- Height
- Width/Length
- Rotation
- Shape
- Building materials
- Evaluators
- Solar insolation potential
- Embodied carbon
- Material Cost
- Operation Cost
- Energy use
- Most Important Tradeoffs to Consider
- Maximizing solar potential will result in a flatter building with a greater floor area, but this will result in higher material and operation costs. A larger roof will provide more space for solar panels, but because construction costs increase with height, a larger roof will be more expensive.
- Structure of a truss bridge for car traffic
- Design variables
- Location
- Width (number of lanes)
- Number of bays
- Height above surface of water
- Truss design
- Evaluators
- Safety
- Cost
- Most Important Tradeoffs to Consider
- Higher safety will require more bays and more material (and therefore higher cost).
- Optimize windows for a building
- Design variables
- Locations
- Dimensions
- Number
- Glazing
- Evaluators
- Amount of sun entering building
- Cooling load from sun through windows
- Most Important Tradeoffs to Consider
- Maximizing natural light reduces lighting loads and is important for occupant wellness, but it also results in solar gains which increase cooling loads.
Step 2 - Generative Design Study
- Objective: What office building design with floor area between 1.2 million and 1.5 million sf will result in greatest sustainability and lowest cost?
- Model: Design a building form based on a shape, its size, and its rotation at three heights. Success can be measured through the cost of the building, solar potential, estimated energy use, and energy efficiency
- Design Variables: Base radius, top radius, top rotation, and height of the building
- Constants: Middle radius, middle rotation, floor to floor height, and costs at different heights of building.
- Evaluators: Surface area to volume ratio, building energy use, potential solar PV area, and construction cost
- Interpretation: To maximize potential solar panel area, many generations have a greater top radius than base radius. These options are less structurally stable and therefore not viable.
Step 3 - Generative Design Study Results
The scatterplot compares the construction cost (which we want to minimize) with the surface area to volume ratio (which we also want to minimize). The construction cost is based on the floor area at each level. The surface area to volume ratio is based on surface area and volume and can be used as a proxy for the energy efficiency of a building. A lower value correlates to higher efficiency. I would choose the design with a lower cost and relatively low ratio, prioritizing the cost more.
/w=3840,quality=80,fit=scale-down)
/w=3840,quality=80,fit=scale-down)
I decided to use the design decision for designing the building form. I initially attempted to use the building form I created in Revit for module 5 but was unable to get that to work for generative design. So, I used the 73B1-MatlCostVsPerformance example as a template and edited it. Here is my overall node logic:
The design variables are the base radius, top radius, top rotation, and height of the building. I set the middle rotation to a constant (half of the top rotation) and the middle radius to a constant (average of the top and bottom radii).
I also changed the number of sides to 6, the story height to 12 ft, and the value per sf to $500 at the bottom of the building and $1000 at the top of the building.
The variables I used were the surface area to volume ratio, building energy use, potential solar PV area, and construction cost. The surface to volume ratio was used to evaluate the energy efficiency, assuming that a lower value will result in fewer losses and higher efficiency. The energy use was based on the EUI. I used the site energy from the “U.S. Energy Use Intensity by Property Type” table from EnergyStar for offices (52.9 kBtu/ft2). The potential solar PV area was estimated at 80% of the roof area. The construction cost was estimated based on the floor area at each level, assuming $500/sf for the bottom floor and $1000/sf at the top floor.
