Design and Engineering

Module 3: Design and Engineering

1. Structural Considerations

Cladding systems must withstand environmental forces while accommodating material movement to ensure long-term stability.

A. Wind Loading & Deflection:

• Wind Load Calculations:

• Determined by building height, location, and local wind maps (e.g., EN 1991-1-4 (Eurocode) or ASCE 7 (USA).

• Cladding panels and fixings must resist positive pressure (windward) and negative pressure (suction).

• Deflection Limits:

• Excessive panel bending can cause sealant failure or glass breakage.

• Standards (e.g., ASTM E1300 for glass) specify max deflection (typically L/60 to L/175).

B. Fixings & Support Systems:

• Mechanical Fixings (Bolts, Clips, Rails):

• Must resist pull-out, shear, and fatigue loads.

• Materials: Stainless steel (A2/A4 grade) for corrosion resistance.

• Adhesive Fixing (Silicone, Structural Glazing):

• Used in unitized curtain walls; requires rigorous peel-and-shear testing.

C. Movement Joints & Thermal Expansion:

• Thermal Movement:

• Metals (e.g., aluminum) expand ~24 mm per 10m at 50°C ΔT; joints must accommodate this.

• Movement Joint Design:

• Width: Calculated based on material CTE (Coefficient of Thermal Expansion).

• Location: At building corners, spandrels, and every 10–12m for metal panels.

2. Detailing for Weathertightness

Preventing water ingress is critical to avoid corrosion, mold, and insulation degradation.

A. Sealants & Gaskets:

• Sealant Types:

• Silicone: UV-resistant, flexible (ideal for glass/metal joints).

• Polyurethane: Durable but less elastic (used in panel seams).

• Gasket Systems (EPDM, Neoprene):

• Pre-compressed rubber strips for dry-glazed curtain walls.

B. Drainage Strategies:

• Rainscreen Principles:

• Pressure-equalized cavities with weep holes to channel water outward.

• Open-joint systems for passive drainage (e.g., terracotta rainscreens).

• Drip Edges & Flashings:

• Redirect water away from critical joints.

C. Air/Water/Vapor Barriers:

• Air Barriers:

• Reduce infiltration (e.g., self-adhesive membranes).

• Vapor Barriers:

• Prevent condensation (placed on the warm side of insulation).

• Testing:

• ASTM E1105 (water penetration) and ASTM E2178 (air leakage).

3. Digital Tools

Advanced software enhances precision in cladding design and performance analysis.

A. BIM Integration (Revit, ArchiCAD):

• 3D Modeling:

• Clash detection between cladding and MEP systems.

• Parametric Design:

• Automated panelization for complex geometries (e.g., curved façades).

B. Thermal Modeling (THERM, Flixo):

• Condensation Risk Analysis:

• Simulates temperature gradients and dew points.

• U-Value Calculations:

• Validates compliance with energy codes.

C. Structural Analysis (ANSYS, ETABS):

• Finite Element Analysis (FEA):

• Tests cladding under wind, seismic, and live loads.

Key Takeaways:

1. Structural integrity hinges on wind load resistance and proper joint design.

2. Weathertightness relies on layered sealing and drainage strategies.

3. Digital tools optimize design accuracy and regulatory compliance.

Next Steps:

• Explore case studies of cladding failures due to poor detailing?

• Dive deeper into BIM workflows for façade engineering?

• Concrete/metal substrates must be cured, clean, and free of contaminants (e.g., dust, oil).

• Primer application (e.g., epoxy-based for metal) enhances adhesion.

• Sequential Checks:

• Pre-installation: Verify panel dimensions, batch consistency.

• During Installation: Inspect sealant application, fastener torque.

• Post-installation: Water spray testing (e.g., AAMA 501.2) for leaks.

• Tolerance Management:

• Shim adjustments for misaligned substrates.