what is a curtain wall when you see a skyscraper with walls of glass glistening in the sunlight or luxurious floor-to-ceiling windows overlooking snowy mountains? Those are curtain walls, a non-loadbearing wall system that uses aluminium frames to support large glass panes and encourages natural light into the building.

As the outer skin of a building, curtain walls must resist air and water infiltration; wind and seismic forces that may act upon the building; and thermal expansion and contraction. They also must provide protection for occupants against corrosive elements and fire hazards.

The non-structural nature of curtain walls allows them to be constructed with much lighter materials than traditional load bearing walls, reducing the overall construction costs of a building. However, the walls transfer lateral wind loads to the main building structure through connections at floors and columns of the building. This limits the maximum height of a building that can be built with curtain walls and the size of the window openings.

Exploring the Concept: What Exactly is a Curtain Wall

In curtain walls, glazing infill is held within an extruded aluminium frame that can be joined to the rest of the building structure at floors and columns through joints or clips (mullions). Most systems use a stick system with long pieces (referred to as sticks) that are welded together or snapped along the lengths of the mullion to form larger units, which reduces construction time on site.

Curtain wall systems must be designed to ensure the insulating value of the glazed unit is maintained throughout its life, and the airtightness of the insulated glass is sufficient to prevent moisture infiltration, condensation and mould growth. The service life of the glazed unit and the metal framing can be extended by using a gasket material that can be replaced if it becomes damaged or contaminated over time.