What Is a Curtain Wall vs. Window Wall?
A curtain wall hangs from the building's floor slabs as a continuous non-structural facade outside the slab edge; a window wall sits between floor slabs, spanning floor-to-floor within the structural frame. Curtain walls suit towers and high-performance envelopes; window walls suit mid-rise residential where cost matters. The structural engineering differs: curtain walls need anchor design for cladding loads, window walls need deflection compatibility with the frame.
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Structural behavior
Curtain wall anchors carry the facade's dead load and wind load back to the slab edge — the structural engineer designs the embeds and verifies slab edge capacity for the anchor forces. Window walls bear on the slab at each floor and span vertically between, so the frame's interstory drift directly loads the glazing — the engineer sets drift limits the facade can tolerate. Both systems move with the building; the detailing must let them.
Performance and cost
Curtain walls offer superior air/water/thermal performance (unitized systems are factory-glazed and tested) at $80-$150+ per square foot installed. Window walls run $50-$90/sf with more field-assembled joints and more leak risk at the slab interfaces. Energy code compliance is easier with curtain wall thermal breaks; window wall slab-edge thermal bridging needs careful detailing.
Coordination essentials
The facade consultant and structural engineer coordinate anchor locations, loads, and installation tolerances early — curtain wall anchors cast into the slab edge cannot move after the pour. Deflection criteria for the supporting structure come from the facade's limits, not the code minimums. Mock-up testing (AAMA 501) for custom systems is specified when performance is critical.
The bottom line
Curtain wall hangs outside the slab (towers, high performance); window wall spans floor-to-floor (mid-rise, lower cost). Coordinate anchors before the pour and design structure to the facade's deflection limits.
Torch Engineering PLLC · (480) 490-0064 · info@torchengineering.com — PE stamping backed by Apex Grid Engineering.