Curtain Wall Glazing
A Structural Curtain Wall system is an outer covering of a building in which the outer walls are non-structural, but merely keep the weather out and the occupants in. As the curtain wall is non-structural it can be made of lightweight material, reducing construction costs. When glass is used as the curtain wall, a great advantage is that natural light can penetrate deeper within the building. A curtain wall is designed to resist air and water infiltration, sway induced by wind and seismic forces acting on the building, and its own dead load weight forces. Curtain wall systems are typically designed with extruded aluminum members. Curtain walls differ from store-front systems in that they are designed to span multiple floors, and take into consideration design requirements such as thermal expansion and contraction; building sway and movement; water diversion; and thermal efficiency for cost-effective heating, cooling.
Categories of Curtain Wall Fabrication
1. Unitized System
2. Semi Unitized System
3. Stick System
The unitized curtain wall is a façade maintenance system that the unitized panel assembled by various components of curtain wall (including glass panels, supporting frame, etc.) in factory, then delivered to site for hanging installation of which components are fixed to main structure by pre-embedded Connecting Parts.
For unitized curtain walling, about 30% of the work is done on-site, while 70% is carried out in the factory. The complete assembly of the units in the factory brings several benefits.
Improved quality control
Concurrent manufacture and site preparation - units can be assembled while the structural frame is being built.
The facade can also be completed a floor at a time, allowing parallel internal work
Quicker installation, requiring less manpower on site
This system is mainly used in high rise building. This does not require exterior supports like cranes or scaffolding. Only mini cranes or a temporary hoist can be held over the floor to keep it helpful during installation.
Can be installed from the interior of the building. This is ideal for high towers or building sites where there is a tight footprint
Less space is needed on site for layout
Semi Unitized System
Semi-unitized Curtain Wall has the combined features of stick curtain wall and unitized curtain wall. Semi unitized system vertical mullions and horizontal transoms are installed on brackets which are anchored to the columns/slabs. Glass is structurally glazed to the aluminum subframe by the structural sealant.
Advantages of Semi-Unitized Glazing
The vertical mullions in most semi-unitized glazing systems can span two floors with ease and as a result, provide greater structural efficiency.
Most semi-unitized glazing systems have shop-assembled or off-site assembled frames. This reduces the time and cost.
Reasonable selection and usage of material
Stick curtain walling systems are versatile and allow for the integration of other systems, such as sliding doors and windows. They tend to be less specialized and can be built by all types of fabricators as they are not dependent on having a large factory.
However, stick systems do require multiple steps to erect and seal the wall, which means more time is spent on-site – an approximate rule of thumb would be that 70% of the work is carried out on-site, with 30% in the factory. This incurs further costs, such as laborer's time.
Wide availability of system choice on the market at very competitive prices and short lead-in times
Suited for angular or complex facades
Sightlines are slimmer than Unitized Curtain Walling
Quicker production processes in the factory
Sequence of the building can be changed quickly