Create Two New Evaluator Custom Nodes (2 units)
For this assignment, I created four custom nodes to evaluate the performance of the building form alternatives. These metrics help compare each building form not only by its geometric properties, but also by its cost, structural efficiency, envelope efficiency, and environmental performance.
Custom node 1: Estimation cost
The first custom node estimates the cost efficiency of each building form. This node is based on the example provided in the CEE 220C library, but I modified it by adding a calculation for cost per usable square foot. The node first calculates the total estimated cost of the building form. Then, it divides the total cost by the total floor area
This metric is useful for comparing different building forms from a developer’s perspective. A lower cost per square foot indicates a more cost-efficient design alternative.
Custom node 2: Slenderness ratio
The second custom node calculates the slenderness ratio of the tower. This metric is important because a taller and narrower building is generally more sensitive to lateral loads such as wind and earthquakes.
In Dynamo, I used Element.GetParameterValueByName to extract the tower height and the two base width values. Then, I used Math.Min to determine the smaller base width. Finally, I divided the tower height by the minimum base width
A higher slenderness ratio indicates a more slender building form, which may require a more efficient lateral force-resisting system and could lead to larger lateral drift.
Custom node 3: Surface to Volume ratio
The third custom node calculates the surface-to-volume ratio of the building form. This metric evaluates how compact the building form is. The node uses Element.GetParameterValueByName to extract the gross surface area and gross volume from the Revit mass. Then, the surface area is divided by the volume
A lower surface-to-volume ratio generally means the building is more compact. This can reduce heat loss, decrease facade material requirements, and improve energy efficiency. A higher ratio means that more envelope area is exposed per unit of building volume, which may increase facade cost and environmental loads.
Custom node 4: Solar radiation analysis
The fourth custom node evaluates the solar radiation received by the building surfaces. This node is based on the solar analysis custom node provided in the CEE 220C library.
The workflow sets the project location, sun settings, weather data, and the start and end date of the analysis period. Then, SolarAnalysis.Analyze is used to calculate the cumulative solar radiation on the building surfaces.
This metric helps evaluate how much solar exposure each building form receives. It is useful for understanding daylight potential, solar heat gain, and possible opportunities for photovoltaic panels or shading design.
Final results:
Point to Ponder: Do the new evaluation metrics that you’ve designed capture the meaningful differences between the building form alternatives?
Yes. The new evaluation metrics capture meaningful differences between the building form alternatives because they evaluate more than just basic geometry. The slenderness ratio helps compare the structural efficiency and lateral stability of each form, while the surface-to-volume ratio evaluates how compact and environmentally efficient each form is. These metrics show that two buildings with similar floor area or volume can still perform very differently depending on their height, base width, and envelope exposure.
The estimated cost metric also helps compare the alternatives from a developer’s perspective, while the solar radiation analysis provides information about daylight potential and solar exposure. Together, these metrics make it easier to understand the tradeoffs between cost, structure, energy performance, and environmental quality.
Develop a Single-Objective Optimization Scheme(3 units)
Point to Ponder: What overall strategy do you feel best captures the relationship between the evaluation metrics?
The overall strategy of this optimization scheme is to balance the tradeoffs between structural performance, environmental efficiency, construction cost, and solar performance rather than maximizing a single metric independently. Since the evaluation metrics have different units, scales, and performance directions, all metrics were first normalized into values between 0 and 1 so they could be fairly compared and combined into a unified evaluation framework. Metrics that represent more efficient performance with lower values, such as slenderness ratio, surface-to-volume ratio, and estimated cost, were inverted after normalization so that higher normalized values consistently represent better performance across all categories.
For metrics in which a lower value represents better performance, such as slenderness ratio, surface-to-volume ratio, and estimated cost, the normalized values were inverted so that a higher normalized score always indicates better performance. For the cumulative insolation metric, higher values were considered beneficial because they indicate greater daylight and solar energy potential.
After normalization, weighting factors were assigned to reflect the relative importance of each metric in the design decision. Estimated cost was given the highest weight because cost efficiency is one of the most important considerations from a developer’s perspective. Slenderness ratio was also heavily weighted because it relates to structural stability and lateral performance. Surface-to-volume ratio was weighted moderately because it affects environmental efficiency and facade material usage. Solar insolation was assigned a smaller weight because, although daylight access is valuable, excessive solar radiation may also increase cooling demand.
Result:
Based on the combined evaluation score, the top three recommended design alternatives are:
- Top Height = 1201, Tower Base Side = 200 Combined Score = 9.54
- Top Height = 1201, Tower Base Side = 150 Combined Score = 7.94
- Top Height = 1302, Tower Base Side = 200 Combined Score = 7.26
Among these alternatives, the building form with a top height of 1201 and a tower base side length of 200 is considered the best overall design option because it achieved the highest combined evaluation score. Compared to the taller tower configurations, this alternative maintained a relatively low slenderness ratio, indicating better structural stability and lower potential for excessive lateral drift. At the same time, it achieved one of the best surface-to-volume ratios, meaning the building form is more compact and environmentally efficient. The estimated cost also remained relatively efficient compared to the larger and taller tower forms. In addition, the design still maintained strong cumulative solar potential values, providing good daylight and solar exposure opportunities without significantly sacrificing the other performance metrics.
Point to Ponder: What propelled the recommended alternative to the top of the list? The recommended alternative was propelled to the top of the list because it achieved the best balance between all of the competing evaluation metrics rather than only excelling in a single category. Although some alternatives produced larger floor areas or higher solar exposure, they also introduced disadvantages such as higher slenderness ratios, increased façade exposure, or greater estimated construction cost.