/facade-computation

title: Facade Computation
description: Panelization strategies, surface rationalization, attractor-based patterning, double-skin facades, kinetic and responsive facades, environmental performance facades, and fabrication-aware facade design for AEC
version: 1.0.0
tags: [facade, panelization, rationalization, curtain-wall, kinetic, double-skin, shading, cladding, environmental-facade]
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invocation: /facade-computation

Facade Computation

1. Computational Facade Design Philosophy

The building facade is not a wrapper. It is the single most consequential architectural element — the mediator between interior environment and exterior climate, the primary determinant of energy consumption, the structural skin that must resist wind, seismic, and thermal loads, and the public expression of a building's identity. Computational facade design treats every square meter of this surface as a field of optimizable variables rather than a repeating module selected from a catalog.

Facade as Environmental Mediator

Every facade simultaneously manages five environmental flows:

| Flow | Inward | Outward | |------|--------|---------| | **Solar radiation** | Daylight, solar heat gain | Glare, overheating | | **Thermal energy** | Heat loss in winter | Heat gain in summer | | **Air** | Natural ventilation, infiltration | Exfiltration, stack effect | | **Moisture** | Rain penetration, condensation | Vapor diffusion | | **Sound** | Exterior noise intrusion | Interior noise escape |

A computationally-driven facade optimizes across all five flows simultaneously, varying panel geometry, material, porosity, and depth point-by-point across the surface based on orientation, local microclimate, interior program, and structural constraints.

Integration of Performance, Structure, and Aesthetics

Traditional practice separates these into different consultancies — the architect draws the pattern, the structural engineer sizes the mullions, the facade consultant specifies the glass, and the energy modeler checks compliance. Computational facade design collapses these into a single parametric model where every design decision is simultaneously evaluated against structural, thermal, daylight, acoustic, and aesthetic criteria. The parametric model is the single source of truth, and downstream deliverables — shop drawings, energy models, structural calculations, panel schedules — are all derived outputs.

The Shift from Standard Curtain Walls to Computationally-Derived Systems

Standard curtain wall systems (stick-built or unitized) impose a regular orthogonal grid with fixed mullion depths and standardized infill panels. This approach optimizes for fabrication simplicity and erection speed at the cost of environmental performance — every panel on the building receives the same glass, the same SHGC, the same U-value, regardless of whether it faces north or south, is at ground level or the 60th floor, or fronts an office or a server room.

Computational facade design replaces this uniformity with gradient variation:

• Glass type varies by orientation and floor level
• Mullion depth varies by wind pressure zone
• Shading device angle varies by solar exposure
• Panel porosity varies by ventilation requirement
• Panel size varies by structural span and visual rhythm

The result is a facade that performs 30-50% better than a uniform curtain wall while often using less material, because material is concentrated where loads demand it rather than uniformly distributed.

Facade as a Data-Driven Element

Modern computational facades are designed from data, not from intuition:

• **Solar radiation maps** (kWh/m²/year per panel) drive shading geometry
• **Wind pressure coefficients** (Cp values from CFD or wind tunnel) drive mullion sizing
• **View analysis** (percentage of sky visible, view direction quality) drives glazing transparency
• **Daylight autonomy targets** (sDA, ASE) drive aperture size and light redirection
• **Acoustic mapping** (dB levels from traffic, aircraft) drives acoustic performance requirements
• **Structural analysis** (gravity, wind, seismic, thermal movement) drives connection design
• **Cost models** ($/m² by panel type) drive rationalization strategies

Each of these data layers becomes an input field that the computational model reads and responds to, producing a facade that is locally optimized everywhere.

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2. Panelization Strategies

Panelization is the process of decomposing a continuous design surface into discrete, fabricable panels. The choice of panelization strategy determines fabrication cost, structural behavior, weatherproofing strategy, and visual character.

2.1 Planar Panelization

Planar panels are the most economical to fabricate because flat glass can be cut from stock sheets without any forming process.

Quad Panels from UV Subdivision

The simplest approach: subdivide the surface along its natural UV parameter lines to produce quadrilateral panels. On a planar or single-curved surface, these quads are inherently planar. On a double-curved surface, they will deviate from planarity.

**Planarity tolerance**: Industry standard is < 2mm deviation of the fourth corner from the plane defined by the other three corners. For structural silicone glazing, tolerances tighten to < 1mm. For mechanically captured glazing with gaskets, up to 3mm may be acceptable depending on gasket profile.

**PQ-mesh (Planar Quadrilateral Mesh) generation methods**: 1. **Conjugate curve network**: Identify two families of curves on the surface that intersect at consistent angles. If the curves follow conjugate directions (where the second fundamental form vanishes), the resulting quad mesh will have planar faces. On a surface of revolution, meridians and parallels are conjugate. On a translational surface, the two generating curve families are conjugate. 2. **Conical mesh construction**: A mesh where all vertices have the property that