Curtainwall: Not Just Another Pretty Façade

11/02/2006 |

Many factors affect the performance of curtainwall and can lead to deterioration and failure if not addressed

They’re unique, aesthetically pleasing, and provide a barrier to the elements: Curtainwall systems have not only evolved, they’ve grown increasingly popular in building construction. In a nutshell, a curtainwall literally hangs from a structure like curtains hang on a wall. A curtainwall system is any exterior wall that is attached to the building structure (but is not load-bearing).

A curtainwall is the façade element that forms the weather barrier for the building without supporting the structure. It can have many different appearances, but typically has narrowly spaced vertical and horizontal mullions with glass, stone, metal, or composite panels. When designed properly, it is beautiful and highly functional in keeping the elements out and the temperate environment in.

Curtainwall first appeared on the scene in 1918; by the mid-1930s, new technology paved the way for developments in metal curtainwall panels. After World War II, metal and glass curtainwall systems started appearing on commercial and institutional buildings. Large areas of glass became possible in the 1950s with the newly invented float process. Insulated glazing, air-conditioning, and insulation technology helped solve the heating and cooling issues that accompanied large areas of vision glass.

Different types of curtainwall include the stick system (pictured here), unit panel system, unit mullion system, column cover and spandrel systems, and point-loaded structural glazing systems.

Many factors affect the performance of curtainwall and can lead to deterioration and failure if not addressed in a proper and timely fashion. Weather (wind and rain) is a leading source of deterioration to the exterior components of a building. Gasket- and sealant-material selections are critical in preventing air and water infiltration; inferior quality can lead to early disintegration and failure. Proper panel installation is key.

Leaks in a curtainwall, in the forms of both air and water, can contribute to indoor air-quality problems by supplying liquid water and condensation moisture for mold growth. Water or condensation can often remain hidden within the wall system and not become evident until concealed wall components experience significant deterioration and mold growth, requiring costly repairs or replacement.

Preventing water penetration is critical when designing and constructing a curtainwall. Many curtainwall systems include condensation drainage provisions that collect and weep condensate from spandrel areas to the exterior.

Building-code requirements govern many aspects of curtainwall design, such as type and thickness of glass, maximum permitted glass area, design wind loads, and firestopping of wall cavities. Close cooperation between the architect and builder helps eliminate potentially hazardous conditions.

Routine inspections and evaluations help identify issues that can arise and compromise your curtainwall’s efficiency. Thoroughly check the system’s gaskets, seals, system joints, and thermal insulation capabilities of the vision and insulating panels.

There are a variety of assessments to measure how well your curtainwall system is performing. These tests include measuring air leakage, water resistance, water drainage, wind resistance, ability of the curtainwall to support its own weight, safety, and thermal performance.

Russell M. Sanders is executive vice president and director, technical services, at Hoffmann Architects Inc., specialists in the rehabilitation of building exteriors. Hoffmann Architects ( has offices in New York City; Washington, D.C.; and Hamden, CT.

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