When would an architect choose a semi-unitized over a unitized curtain wall?

An architect would typically choose a semi-unitized curtain wall in scenarios that require a blend of the quality control found in fully unitized systems and the on-site flexibility offered by stick-built systems. A semi-unitized system is a hybrid approach. It involves pre-assembling some components in the factory—often mullions and transoms, or even small ladder-like frames—which are then shipped to the site. The final assembly, including the installation of glazing and panels, is completed on location. This method is particularly advantageous for projects with complex or varied facade designs that may not be suitable for the repetitive nature of a fully unitized system. For example, a building in Riyadh with intricate angles, custom facade features, or frequent changes in plane would benefit from this approach. The semi-unitized system allows architects more design freedom and the ability to make on-site adjustments, which is more difficult with fully fabricated unitized panels. It can also be a practical choice for mid-rise buildings where the full investment in unitized fabrication logistics may not be justified, but a higher quality than a standard stick-build is desired. It strikes a balance by moving some of the critical assembly work into a controlled factory setting to improve quality, while still allowing the flexibility to accommodate unique architectural details on site. It essentially serves as a middle ground, offering a step up in quality and speed from stick systems without the rigid modularity of fully unitized curtain walls, making it ideal for unique architectural visions across Saudi Arabia.