Applying a single facade-wide pressure value to a curtain wall system understates pressure on the highest-risk spans, because mullion spans and glazing unit sizes vary significantly across the elevation in ways a single value cannot capture.
Why Curtain Wall Pressure Cannot Be a Single Number
Curtain wall systems distribute wind load through mullions and glazing units of varying spans and tributary areas across a single elevation. The effective wind area for a short-span mullion differs from that of a long-span mullion, and pressure coefficients scale with effective wind area — meaning a single facade-wide pressure value cannot correctly represent every span condition present on a real curtain wall elevation.
Where the Single-Value Simplification Breaks Down
Engineers applying one pressure value across an entire curtain wall system are effectively assuming uniform span conditions across the elevation — an assumption that rarely holds on facades with varying floor-to-floor heights, mixed glazing unit sizes, or transition zones between different curtain wall configurations. The spans that most diverge from the “typical” assumption are exactly where an undersized pressure value creates real risk.
Why This Matters Most at the Highest-Risk Spans
The mullion spans and glazing units most likely to experience the highest actual pressure — often at building corners, at unusually long spans, or at transitions between curtain wall types — are precisely the locations where a single averaged pressure value is most likely to understate the true design requirement.
Mapping Pressure to Specific Spans and Zones
After explaining why curtain wall pressure varies by mullion span and tributary area, the fix is calculating pressure values specific to each span and zone configuration present on the actual elevation, rather than applying one representative value across the whole system. Wind Master maps pressure values to the specific spans and zones the curtain wall system requires, ensuring the highest-risk spans receive pressure values calculated for their actual tributary area rather than a generalized facade-wide assumption.
Validate your curtain wall pressure inputs — Audit your span-specific zones.