Façade or curtain wall is a building envelope creates pleasure aesthetic to the building exterior. These are aluminium framed, the non-load bearing system which are hanging from the floor slabs and columns. The curtain wall construction is classified as two as stick system and unitized system.
Stick System
This is mostly adopted in low rise and mid-rise buildings. In this system, most of the erection and fabrication are done at the site. In cases where the wall configuration seems as complex and having more corners and drastic changes in the plane, the stick system would be more economical.
Aluminium frame for the stick system is shown below.
Unitized System
Unitized systems are fabricated in a controlled environment and brought to the site for the installation. So, large-sized glazing shall be fabricated with high quality and low tolerance in dimensions. This is extremely beneficial to the site peoples as the speedy installation can be done within a short time period as no onsite glazing or fixing is required. Only one-third of the time is required compared to the stick system installation. So, in cases where a larger area to be covered with the curtain wall, this unitized system shall be chosen. And also, for high rise buildings where the wind loadings and aerodynamic effects are dominating, higher stability and better performance can be achieved by these regular unitized panels. More than that, unitized panels are more acoustic barrier as it is incorporated with a gasket layer which prevents the noise transfer from one floor to another.
Single modular unit before installation is shown in the below figure.
On the other hand, this installation requires extra transportation to bring the fabricated panels, and special equipment needed for the installation.
Stick System Vs Unitized System
Generally, the choice of the system depends on the following aspects
- location of the installation
- project size
- number of repetitions
- rate per labor
- space at the site
Structural Concept
Transoms and mullions are the structural aluminium frames which 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. Generally, these frames are hanging from the top floor and having lateral support at the below floor to resist the wind suction.
Connection configuration for the unitized curtain wall system is shown in the below figures.
