Unitized Curtain Wall Calculator

Stack Joint Size takes the largest of three movement sources -- floor slab deflection (L/360), aluminum thermal expansion, and seismic inter-story drift -- applies a 1.5x safety factor, then clamps the result between a 20 mm floor and a 75 mm ceiling. Raising Seismic Drift Ratio never narrows the joint (it only ever holds steady or widens it, once seismic drift becomes the governing term), but the 75 mm cap means an aggressive drift ratio near the top of the 0.001-0.02 declared range stops moving the joint size well before the ratio itself maxes out.

One thing only: Floor-to-floor Height, copied straight across as Panel Height in millimetres -- there's no averaging, adjustment, or code check involved, because a unitized system's defining feature is that the factory ships one panel per story. Compare that to Panels Per Floor, which DOES get computed (Facade Width divided by Target Panel Width, rounded up) -- the vertical dimension of a unitized panel is fixed by definition, while the horizontal dimension is the one actual design variable the panel-sizing math solves for. That asymmetry is why changing Facade Width, Number of Stories, Target Panel Width, or Seismic Drift Ratio reshuffles how a facade divides horizontally but can never touch the one number that was never really a calculation in the first place.

No -- Total Facade Area always comes out to the same number, Facade Width times Facade Height (Number of Stories times Floor-to-floor Height), no matter where Target Panel Width sits in its 0.6-4 m range. Slicing the facade into more, narrower panels changes Panels Per Floor and Actual Panel Width, but the sum of all those panel areas is still the same fixed rectangle -- the target width only decides how finely that rectangle gets divided, never how big it is.

Panels Per Floor is Facade Width divided by Target Panel Width, rounded UP to a whole panel -- rounding up (rather than down) means the facade's width always gets covered by whole panels, but it also means each panel usually ends up slightly narrower than requested so the panels split the facade width evenly with no leftover sliver bay.

Number of Stories is purely a repetition count -- each additional floor adds one more ring of Panels Per Floor panels, stacked identically on the one below, which is why Total Panels and Total Weight scale directly with it. Panel Weight, Stack Joint Size, and Seismic Drift, though, are each computed from a single floor's geometry and movement (Floor-to-floor Height, Seismic Drift Ratio, Facade Width, Target Panel Width) -- properties of one repeated unit, not of how many times that unit gets repeated. A 5-story and a 50-story building with identical floor plans and drift ratios get exactly the same Panel Weight and Stack Joint Size; only the totals climb.