Step 1 - Generative Design Framework
For this exercise, we have studied three different design decisions. The natural ventilation potential of the building, implementing green roofs, and the view quality of the building.
Maximising Natural Ventilation Potential
Design Variables
- Climate
- Building height
- Building volume
Evaluators
- Building height to volume ratio: evaluate the building’s height vs its volume. A tall and skinny building will help enhance natural ventilation by creating a convection chimney effect.
- Building’s energy consumption or site EUI: energy Use Intensity of the building (HVAC, lighting, etc.)
- Percentage of daylight in the building: having more daylight helps to enhance natural ventilation by creating natural “hot” spots which induce vertical convective heat transfer in the building.
- Window to wall height ratio: how much surface area do the windows account for the whole building
- Building’s solar insulation: how much solar energy does the building receive
- Building cost.
Most Important Tradeoffs to Consider
- Building height to volume ratio vs. percentage daylight: how the height to volume ratio will impact the percentage of daylight in the building and this its natural ventilation potential.
- Wtw ratio vs. percentage daylight: how much does the window sizing affects the percentage of daylight received in the building in strategic places and tradeoffs with cost + building insulation + site EUI (large energy losses with bigger windows).
- Building height to volume ratio vs. building’s solar insulation: how much does the height to volume ratio affects a building’s ability to receive solar energy.
- All evaluators vs. building cost: help assess how improving each parameter affects the overall construction cost of the building.
Green Roofs
Design Variables
- Garden size: width vs. length → total surface area
- Climate: directly impacts the quality of green roofs
- Project location
- Roof size
Evaluators
- Cost of materials: how much more $ is required to build x-ft of green roof
- Heating/cooling savings: how much does a green roof help reduce cooling and heating consumption per SF
- Water usage: how much extra water consumption for the building per SF of green roof
Most Important Tradeoffs to Consider
- Cost vs. energy savings: this tradeoff defines whether the additional cost of building the green roofs will results in greater energy savings for the whole building.
- Cost vs. water usage: idem, but here for water consumption. We should expect to consume more water, and therefore project location matters as water may be more scarce/expensive
- Energy savings vs. water usage: idem as previous tradeoffs, do the energy savings justify a greater water consumption?
City Views
Design Variables
- Exterior surface areas
- Building height
- Building shape
- Adjacent buildings
Evaluators
- Materials costs: how much $ is required to build the structure
- Unobstructed sights %: how many unobstructed point of views the building has
- % floor surface area above a certain height: what percentage of the building is located above 600-ft? 700-ft? The higher, the better view!
- Real estate value: building with more unobstructed sights will usually have greater real estate value
Most Important Tradeoffs to Consider
- Materials costs vs. unobstructed sights: what is the tradeoff between the extra $ spent and the number of unobstructed view sights in the building? Does spending more justifies a few more nicer views
- Materials costs vs. number of floors above a certain height: idem previous point.
- Material costs vs. real estate value: this time, however, real estate also symbolises return on investment; a larger real estate value means more revenues from exploiting the building. What is the relationship between the overall cost of the building, and how much return on investment it could bring in the future?
Step 2 - Generative Design Study
For this part of the assignment, we have decided to look at the natural ventilation potential of the building. Our goal is to design a building to maximise the building height to volume ratio, percentage of daylight, and solar insulation, as well as minimise the total cost of the building. For this, I created a simple tubular tower that can be adjusted at three different sections (bottom, middle, and top).
Design variables
- Midsection width
- Midsection lateral offset
- Top section width
- Top section lateral offset
- Building height
Constants
- Building location, climate, and time of the day
- Floor-to-floor height
- Bottom section width
- Construction costs inputs
Evaluators
- Height to volume ratio
- Percentage of daylight
- Cumulative solar insulation
- Building cost
The results obtained for this analysis are discussed in the following part.
Step 3 - Generative Design Study Results
For this example, we have chosen to compare the tradeoffs between the solar insulation and construction cost.
Figure 1. Scatter plot of our design choices
From the figure above, we can see that there’s a clear relationship between the building’s solar insulation and its construction cost. The most performant case is one where the bubble is the farthest to the left and up - ie low construction cost and high solar insulation. We can size that there is a relationship with the percentage of daylight and height to volume ratio. The scenario most to the left have shown the best results for these two metrics.
Figure 2. Best Design
The best design for this example is highlighted in figure 2 above. The design choice has an overall low construction cost, and a relatively high solar insulation. For designs with similar solar insulation, it is by far the cheapest design. It also has a relatively good percentage daylight and height to volume ratio, making it ideal for natural ventilation.
Figure 3. Alternative option
The alternative option shown above is by far more expensive. However, it yields a better solar insulation. Its percentage of daylight is decent, but it has a mediocre height to volume ratio. This design could be recommended for projects that do not value construction cost as a major criteria in their design, but look at a more performance-oriented building.
Figure 4. Dynamo Study Graph
The figure above shows the dynamo logic for this study. Groups to the left of the graph allow to build the structure, whereas groups to the right help calculate the different outputs for this study. The same logic from Module 6 was used to compute the building’s solar insulation, height to volume ratio, and percentage of daylight. For the building cost, we said that the SF price will grow linearly from $700 per SF at the ground level to $1500 per SF at 750’ above the ground. We added the cost of installing exterior panels by multiplying the exterior surface area of the building by a price $40 per panel.