Step 1 - Generative Design Framework
Step 1
- Construction cost: variables that affect construction cost including labor costs, project location, complexity of design, size of design, and material selection. Construction cost is typically evaluated based on monetary value, but other cost evaluators could be operating versus capital costs.
- Sustainability: variables that affect sustainability include building materials, building design, and energy efficiency of building components (i.e. HVAC). Sustainability can be evaluated using metrics such as site EUI, source EUI, or LCAs and typically need to also consider costs.
- Energy efficiency: energy efficiency can be bundled into sustainability design decisions but can also be a decision on its own. Major variables are cost (both opex and capex) versus energy savings. Sometimes energy efficient designs can be aesthetically pleasing but can also have tradeoffs between what looks “normal” and what is energy efficient.
Step 2 - Generative Design Study
- Evaluators
- Cost to construct based on the number of floors
- Due to cost constraints, we want to minimize the cost to construct
- Assume higher floors cost more to construct
- Surface area to volume ratio (assuming the walls are mostly windows)
- Maximize surface area to maximize views and solar heat gain (assuming this building is located in an area where heating is the main energy requirement)
- Site EUI
- Minimize the Site EUI to reduce operation costs and environmental impact.
- For this building, assume an Office Space with an average Site EUI of 52.9 kBtu/sqft (per EnergyStar suggestions)
- Design Variables
- The building will be a created by lofting 3 circle shapes together
- The height will be set at 750ft (assuming the height is regulated by local codes and the building owner wants the building to be as tall as possible)
- The main design variable we will change is simply the radii of the 3 lofted circles. The radii changes the floor area, which affects the cost, surface area to volume ratio, and site EUI.
- Base Radius
- Mid Radius
- Top Radius
Step 3 - Generative Design Study Results
As mentioned above, the building is created by lofting 3 circles together. The height is a constant of 750 ft and the radii of the 3 circles are the design variables studied.
‘The surface area to volume ratio is found by simply dividing the surface area by the volume of the lofted building.
The building volume was intersected with floors which are 10 ft apart.
Once the floors are created, the area of the floors is calculated. For cost of construction, we assumed the lower levels are cheaper to construct than the upper levels. A linear function is used wherein the lowest level costs $500/sqft to construct and the topmost level costs $1500/sqft to construct.
Using the total floor area, we assumed site EUI is an average of 52.9 kBtu/sqft for an office building.
From the graph, we can see some building options which minimize construction cost and site EUI and maximize surface area to volume ratio. Since cost and site EUI are functions of floor area, we can see that the more expensive buildings also typically have higher site EUI. Also, as shown in the filtered view of the graph, the best performing building typically have a Base Radius in the around 60-80 ft and a Mid Radius of 10-40 ft, with more variability in the Top Radius. Using this info, we could narrow in on the Base and Mid Radius and explore more options in the Top Radius design.
