Original Building Form
Mid Star Rotation: 5 degrees
Tower Height: 300 feet
Recommended Building Form
Mid Star Rotation: 40 degrees
Tower Height: 100 feet
The purpose of this assignment was to build upon my work from module 5 and make a recommendation to the developers of the new high-rise building based on the building constraints and design brief.
To evaluate my building form instances I decided that the most important features from the design brief were that the construction cost was reduced, space and solar insolation efficiency. I used a range of values for the building height that stayed below the height limit of 750 feet. I also adjusted the radius of the encompassing circle of the base star to ensure that it stayed within the 300’ x 450’ in plan view limitation.
To evaluate the different building form options, I first calculated the solar insolation potential within the custom node I created in module 5 to create each of the building form instances. Below is the code block I used to achieve this.
I next calculated the total construction cost of the tower using a linear relationship between the height of each of the floor and their sizes. Below is the code block used to achieve this.
Finally I calculated the payback period of each building with the following code block. This code block incorporates the developers desire to minimize the construction cost. I used the average method to calculate the payback period in which payback period = Initial investment/ Yearly Cash Flow. In order to make this calculation I had to make some assumptions and simplifications. I assumed that the size of each apartment will be 740 square feet and the number of apartments in the entire building would be the total gross floor area divided by 740 feet. I also assumed that each tenant would equally pay $3230/month for rent. I found the yearly cash flow by multiplying the monthly rent by 12 months and multiplying it by the number of apartments. In the yearly cashflow I simplified the calculation by neglecting the maintenance fee the developers will likely have to pay annually for the building. The initial investment cost was set to be equal to the construction cost of the tower.
I believe this is a good evaluation metric because it takes a more holistic view of the tower cost. Some design alternatives may be more expensive but have more gross floor area which would allow them to have more apartments which would then reduce the amount of time it would take for developers to break even and vice versa. This node incorporates the trade offs of size and construction cost in an elegant way. Thus making all the building alternatives more fairly comparable.
To rank and make a choice between all the building alternatives I first found the maximum and minimum values of each of the columns which was all the outputs from the building form custom node for all the alternatives. This is shown in the below code block.
I then rescaled the column values and computed the combined score using the custom node shown below. In the custom node I used a weighted average method to rank all the options and I scaled the metrics by order of importance to me. I gave the payback period the highest scale value because I believe it is the most important because knowing that the payback period is lower will help the developers decide which option is the most desirable. Furthermore, shorter payback periods will encourage investors in the building because they know that they will have a return on investment sooner and start getting profits sooner. The next highest rank was the space efficiency. I chose this second because if space is more efficiently used then there is increased potential to further reduce the payback period. Perhaps the developers will be able to put even more apartments in the building. Next is the solar insolation potential, more solar insolation should cut down the cost of lighting the building. However, this in my opinion is a less efficient way of reducing costs. Finally the lowest rank is the construction cost, this is simply because the effects of the construction cost is already captured in the payback period.
The above image shows the maximum and minimum combined score building parameters. My optimization is inversely related to the payback period. Thus the maximum key here is actually the worst performing of the building instances I made and the minimum key is the best performing.
Results
The top three choices are the ones with the lowest combined score because there is an inverse relationship between the combined score and the payback period (my most important metric). The table shown below illustrates that the best option has a mid star rotation of 40 degrees and a height of 100 feet. However this option has the same payback period as the second best alternative. This one ranks higher because it has a slightly higher solar insolation than the next best one. The trade off of picking what I have deemed to be the best option is that it has a lower gross volume, surface area and floor area than some other alternatives.
In general the best alternative is a lot shorter and has more twist than the original building design. This makes intuitive sense because the more height there is the more it will cost to build and the longer the payback period. Additionally, more twist in the middle of the tower allows more surfaces to be hit by the sun as they are twisted away from the shade of higher floors.
