Curtain walls are non-structural exterior enclosures that hang from the building structure rather than bearing loads. But once the decision to use a curtain wall has been made in PPD, the PDD challenge begins: detailing the system so it actually performs.

Two construction approaches dominate. Stick-built systems arrive as individual components, with mullions, rails, and glazing assembled piece by piece on site. Unitized systems ship as pre-assembled, factory-glazed panels that interlock on the building face. Each method creates distinctly different detailing requirements for the architect.

Thermal bridging through aluminum mullions is the single biggest thermal performance concern in curtain wall design. Aluminum conducts heat roughly 1,500 times faster than insulating glass. Without thermal breaks, mullions become direct heat-transfer paths that can cause condensation, occupant discomfort, and energy waste. Detailing the thermal break, whether as a polyamide strip, polyurethane pour-and-debridge, or structural silicone joint, directly affects both thermal performance and structural capacity.

Mullion profile selection controls the wall's structural behavior under wind and seismic loads, its visual proportions, and its ability to accommodate glazing systems. Profile depth, width, and moment of inertia must satisfy deflection limits while the face dimension determines the wall's architectural expression.

Glazing methods range from dry-glazed systems using gaskets and pressure plates to structural silicone glazing that bonds glass directly to the frame. Each method carries distinct implications for water management, thermal performance, replacement access, and the documentation required in construction drawings.

The ARE tests your ability to evaluate these interrelated detailing decisions and judge how changes in one element cascade through the assembly.