What Is a Curtain Wall in Construction?

February 13, 2024

Using a range of glazing, panel and texture options curtain walls allow architects to achieve dramatic designs while providing long term commercial benefits including a high degree of environmental sustainability. Their lightweight construction allows for a large proportion of floor area to be occupied by glass and helps to greatly improve the thermal performance of a building.

Typical curtain wall systems use aluminum frames. They require careful design for thermal performance as aluminum has a relatively high thermal conductivity. To mitigate this problem the frames are typically fitted with a low-conductivity thermal break of a material such as PVC, Neoprene rubber, polyurethane or polyester reinforced nylon. The thermal breaks must be properly positioned relative to the frame system/insulation in order to avoid exposing the aluminum frames inboard of the thermal break to cold air ("short circuiting" the thermal break).

Curtain walls are designed to transfer back to floor or intermediate framing their own dead load and any live loads that may be applied. These might include wind loads on large horizontal areas, snow loads, seismic loads and maintenance loads. These loads must be transferred to the curtain wall connections with sufficient strength for the load and differential movement induced by thermal changes and wind.

Curtain wall systems often incorporate "pressure bars" fastened to the mullions that function as a pressure bearing member and help to retain the glass. These systems also utilize gaskets between the pressure bar and the mullions to provide additional insulation and acoustic isolation. The system must be carefully designed to ensure continuity of the gaskets at horizontal and vertical transitions in order to prevent water infiltration through the cladding/frame interface. In addition, care must be taken to not over apply sealant as too much can plug weep holes and mask leaks requiring difficult troubleshooting.

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