Note on Stage 1 Part 2 — Custom H_Twist_Mass Rotation Limitation: During this stage, I went to office hours with Steffi to troubleshoot rotation issues with the custom H_Twist_Mass conceptual mass family. The H profile would not rotate parametrically with the template's twist parameter because the custom H geometry was not bound to the template's reference planes — a known limitation when pasting a non-template profile shape into the Twisting Tower family. The conclusion from office hours was to move forward with the limitation noted, which informed the decision to rebuild the form in Grasshopper for Stages 2 and 3, where the twist could be applied parametrically without the Revit family editor binding constraints.
Point to Ponder — What's the advantage of exporting the values to Excel?
Exporting metric values to Excel allows direct comparison across multiple parametric test cases in a single table, which Grasshopper and Revit don't display efficiently on their own. Excel also enables sorting, filtering, and quick visual scanning to identify which cases best meet program targets — for example, sorting by GFA to find which configurations land within the 2.5–3.0M SF compliant range, or comparing envelope efficiency ratios side by side. Beyond ranking, Excel is the natural place to layer in calculated values (cost estimates, insolation proxies, compliance flags) that don't live in the parametric model. For a developer audience, the spreadsheet is also the standard deliverable format for design alternatives evaluation.
Point to Ponder — Which pair of input values gives the most desirable result? Which building form would you recommend to the developer and why?
Case 4 (50 floors, taperRatio = 0.8) is the recommended alternative. It is the shortest compliant building at 200m, minimizing construction cost relative to taller compliant alternatives, while still achieving the full 3.00M SF program target. It has the highest envelope efficiency among compliant cases (GFA/Surface = 3.09), which reduces both initial construction cost and ongoing cooling load in Dubai's hot-arid climate. The 0.8 taper preserves enough upper-floor plate to remain leasable as premium units rather than narrowing into small inefficient corner offices. Together these characteristics deliver maximum program with minimum envelope and minimum height — the strongest combination for a premium-luxury developer in Business Bay.
Point to Ponder — Which input tested has the biggest effect on creating a desirable building form?
taperRatio has the larger effect on the desirability of the form. Each 0.1 step in taperRatio shifts GFA by roughly 200,000–300,000 SF and shifts envelope efficiency (GFA/Surface) by approximately 0.13–0.14, which is enough to flip cases between non-compliant (under-program) and compliant within a single parameter step. numFloors has a meaningful effect on GFA as well but operates more linearly and within tighter bounds — three increments of 3 floors each shift GFA by smaller amounts than a single 0.1 step in taperRatio. Because taperRatio simultaneously affects floor area, envelope area, and envelope efficiency, it is the dominant lever for adjusting the form's compliance and economic performance.
Revit conceptual mass family from the CEE 120C/220C Shared Library, placed in a Dubai-located project file with 50 levels at 13 ft floor-to-floor (650 ft total height). Mass floors assigned to all 50 levels for GFA calculation.
Fixed parameters: Twist 45°, Top Depth 50', Base Width 200', Base Depth 100', Building Height 650'
Variable input flexed: Building Top Width
Test Results
Case | Top Width | GFA (SF) | Surface (SF) | Volume (CF) | GFA/Surface |
1 | 200' | 682,561 | 370,713 | 8,798,097 | 1.84 |
2 | 175' | 647,717 | 354,009 | 8,335,756 | 1.83 |
3 | 150' | 612,543 | 337,437 | 7,873,414 | 1.81 |
4 | 125' | 578,030 | 321,024 | 7,411,073 | 1.80 |
5 | 100' | 543,186 | 304,807 | 6,948,731 | 1.78 |
6 | 75' | 508,342 | 288,842 | 6,486,389 | 1.76 |
Observations: Each 25 ft reduction in top width drops GFA by ~35,000 SF, surface area by ~16,000 SF, and volume by ~462,000 CF. The GFA-to-surface ratio decreases slightly with increased taper (1.84 → 1.76), indicating a uniform tower form is marginally more envelope-efficient than a strongly tapered one.
Stage 1 Part 2 — Custom H_Twist_Mass Conceptual Mass Family
Custom Revit conceptual mass authored by pasting an H-shaped profile into the provided Twisting Tower template, then lofting between H profiles at base and top reference levels. Building height: 595 ft (~45 functional floors at 13 ft floor-to-floor).
Form concept: Twin-tower with mid-height sky bridge — two parallel masses connected by a 22m-thick crossbar.
Fixed parameters: Top Rotation 90°, Base Rotation 10°, Top Width 50', Top Depth 20', Top Height 100', Base Width 300', Base Depth 200'
Variable input flexed: Number of office floors (study: how does reallocating floors to non-office uses affect total office GFA?)
Test Results
Case | Office Floors | Non-Office Floors | % Non-Office | Office GFA (SF) | Surface (SF) | Volume (CF) | Compliant (2.5–3M SF)? |
1 | 38 | 7 | 16% | 2,410,112 | 933,881 | 38,543,110 | No - under |
2 | 40 | 5 | 11% | 2,536,960 | 933,881 | 38,543,110 | Yes |
3 | 42 | 3 | 7% | 2,663,808 | 933,881 | 38,543,110 | Yes |
4 | 44 | 1 | 2% | 2,790,656 | 933,881 | 38,543,110 | Yes |
5 | 46 | 0 (over capacity) | — | 2,917,504 | 933,881 | 38,543,110 | Yes |
6 | 48 | 0 (over capacity) | — | 2,980,928 | 933,881 | 38,543,110 | Yes |
Observations: Each pair of floors reallocated from office to non-office use reduces office GFA by ~126,848 SF. Gross Surface Area and Gross Volume remain constant — they describe the form's fixed exterior envelope. Recommended program: Case 3 (42 office floors, 3 non-office floors) — delivering 2.66M SF of office space while reserving floors for ground-floor lobby/retail, mid-height sky lobby/amenity, and one mechanical floor.
Note: The custom H profile geometry was not parametrically bound to the template's dimensional reference planes. Template parameters (Top Width, Base Width, etc.) display in Properties but do not actively drive the H profile shape — a known Revit family editor limitation when introducing non-template profile shapes.
Stage 2 & 3 — Parametric H Tower in Grasshopper (Final Recommended Form)
Custom H-shaped profile authored as a Grasshopper cluster, lofted into a tapering, 90° twisting tower. The 12-point H polyline is parametrically defined by W (overall width), H (overall depth), L (leg width), and B (crossbar thickness).
Form concept: Twin-tower with mid-height sky bridge, twisted 90° from base to crown, tapering from base to top.
Fixed parameters: W = 121m, H = 60m, L = 55m, B = 22m, floor height = 4m, twist total = 90°
Variable inputs flexed (12 cases): numFloors (50, 53, 56) × taperRatio (0.5, 0.6, 0.7, 0.8)
Stage 2 Test Results
Case | numFloors | taperRatio | Footprint (m²) | GFA (m²) | GFA (SF) | Surface (m²) | GFA/Surface |
1 | 50 | 0.5 | 6,842 | 199,849 | 2,151,193 | 74,291 | 2.69 |
2 | 50 | 0.6 | 6,842 | 223,692 | 2,407,927 | 79,410 | 2.82 |
3 | 50 | 0.7 | 6,842 | 249,838 | 2,689,389 | 84,710 | 2.95 |
4 | 50 | 0.8 | 6,842 | 278,288 | 2,995,591 | 90,198 | 3.09 |
5 | 53 | 0.5 | 6,842 | 211,822 | 2,280,019 | 78,158 | 2.71 |
6 | 53 | 0.6 | 6,842 | 237,102 | 2,552,141 | 83,536 | 2.84 |
7 | 53 | 0.7 | 6,842 | 264,822 | 2,850,464 | 89,092 | 2.97 |
8 | 53 | 0.8 | 6,842 | 294,982 | 3,175,025 | 94,834 | 3.11 |
9 | 56 | 0.5 | 6,842 | 223,796 | 2,409,046 | 82,033 | 2.73 |
10 | 56 | 0.6 | 6,842 | 250,512 | 2,696,646 | 87,670 | 2.86 |
11 | 56 | 0.7 | 6,842 | 279,805 | 3,011,915 | 93,483 | 2.99 |
12 | 56 | 0.8 | 6,842 | 311,677 | 3,355,084 | 99,479 | 3.13 |
Stage 3 Performance & Economic Analysis
Case | nF | TR | GFA (SF) | GFA/Surf | Avg $/SF | Total Cost | Insolation (MWh/yr) | Compliant? |
1 | 50 | 0.5 | 2.15M | 2.69 | $719 | $1.55B | 111,437 | No - under |
2 | 50 | 0.6 | 2.41M | 2.82 | $719 | $1.73B | 119,115 | No - under |
3 | 50 | 0.7 | 2.69M | 2.95 | $719 | $1.93B | 127,065 | Yes |
4 | 50 | 0.8 | 3.00M | 3.09 | $719 | $2.15B | 135,297 | Yes |
5 | 53 | 0.5 | 2.28M | 2.71 | $732 | $1.67B | 117,237 | No - under |
6 | 53 | 0.6 | 2.55M | 2.84 | $732 | $1.87B | 125,304 | Yes |
7 | 53 | 0.7 | 2.85M | 2.97 | $732 | $2.09B | 133,638 | Yes |
8 | 53 | 0.8 | 3.18M | 3.11 | $732 | $2.32B | 142,251 | No - over |
9 | 56 | 0.5 | 2.41M | 2.73 | $745 | $1.79B | 123,050 | No - under |
10 | 56 | 0.6 | 2.70M | 2.86 | $745 | $2.01B | 131,505 | Yes |
11 | 56 | 0.7 | 3.01M | 2.99 | $745 | $2.24B | 140,225 | No - over |
12 | 56 | 0.8 | 3.36M | 3.13 | $745 | $2.50B | 149,219 | No - over |
Best in each category (compliant cases only — 3, 4, 6, 7, 10):
- Best envelope efficiency: Case 4 (GFA/Surface = 3.09)
- Highest insolation potential: Case 7 (133,638 MWh/yr)
- Lowest construction cost: Case 3 ($1.93B)
- Highest GFA achieved: Case 4 (3.00M SF)
Final Recommendation: Case 4 — 50 floors, taperRatio = 0.8, 200m height, 3.00M SF, $2.15B construction cost. Highest envelope efficiency among compliant cases (3.09), shortest compliant building height (minimizing construction cost), full program fulfillment at the 3M SF ceiling, and architecturally distinctive form appropriate for Business Bay's high-profile site adjacent to the Burj Khalifa.