A curtain wall is a non-load-bearing exterior wall system attached to the outside of a building’s structural frame, designed to keep out weather while allowing natural light to enter. Unlike traditional masonry walls, a curtain wall carries only its own weight and the forces of wind, transferring these loads back to the primary structure at each floor level.
Applications
Curtain walls became a defining feature of modern architecture in the 20th century, enabled by the development of steel and reinforced concrete frame construction. When the structural frame of a building carries all gravity loads, the exterior wall no longer needs to be massive or load-bearing. This freed architects to design lightweight, transparent facades using glass and metal.
The most common type of curtain wall consists of an aluminum frame (mullions and transoms) fitted with glass panels, though panels of stone, metal, or composite materials can also be used. There are two primary installation methods: stick-built systems, where individual frame components are assembled on-site piece by piece, and unitized systems, where pre-assembled panels are manufactured in a factory and installed as complete units. Unitized systems are faster to install and offer better quality control, making them the preferred choice for tall buildings.
Performance is a critical consideration in curtain wall design. The system must resist wind loads, manage thermal expansion and contraction, prevent water infiltration, and provide adequate insulation. Modern curtain walls incorporate thermal breaks, sealed glazing units, drainage channels, and pressure-equalized cavities to meet these demands.
Energy efficiency has become an increasingly important aspect of curtain wall design. High-performance glazing with low-emissivity coatings, insulated spandrel panels, and integrated shading devices help reduce heat gain and loss, contributing to a building’s overall energy performance.
Iconic examples of curtain wall architecture include the Lever House and the Seagram Building in New York City, both of which helped establish the glass-and-steel aesthetic of mid-20th-century modernism.
Related terms
- Facade engineering
- Mullion
- Glazing
- Cladding
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