As it is well acknowledged, even a well-designed glazing system can be easily degraded by poor installation methods. Curtain walls are generally highly engineered and factory built with close tolerances. However, the placement of these precisely manufactured assemblies on a structure with much greater dimensional tolerances can lead to issues with the overall facade, such as air and water leakage as well as unanticipated repairs.
As a rule, curtain walls are typically installed from the outside, and the panels are lifted into place by a crane or a hoisting rig. If the anchors are not cast directly into the slab, field installation begins with the layout and installation of anchors on the slab edges. The panels are then fastened to the anchors. The curtain wall contractor will rely on the offset lines and elevation benchmarks set by the general contractor. Any error in setting these lines will impact the installation of the wall. All such marks should be set well in advance of the curtain wall construction so as to allow cross-checking and preparation by the curtain wall contractor. In addition, wind is a limiting factor during installation as the panels are heavy and have a large surface area that can be affected by wind and be difficult to place. Extreme cold and extreme heat are also problematic because these systems are designed to close tolerances, and the weather can impact both the worker and the materials being handled. On the other hand, the worse quality of curtain wall buildings can be affected by poor workmanship due to rushed installation, working in inclement weather, having multiple or untrained trades involved, and having complicated design details. Installation issues are not always attributable to the facade/cladding installation. Variations in the tolerances of the building frame elements can be a significant quality issue when installing curtain walls.
Curtain walls have an advantage for adapting to these variations than window walls since they are installed outside of the building and attach to the building at point anchors only. In the current market, transoms and mullions are regarded mostly used curtain wall frames, transferring the loads from the glass panels to the connections. The glazing panels should be designed to resist the wind loads at the specific height while having the required thermal insulation. Transoms and mullions are the structural frames holding these glasses and transferring the loads to the main structure through the connections.
