Curtain Wall systems are defined as thin materials with aluminum frames and contain in-fills of delicate stones, sheet metals, and glass. The mainframe is bonded to the base structure, and it does not carry the load of the building’s roof or floor. The curtain wall supporters transfer the force caused by wind, gravity, and other environmental factors to the construction’s floor line. Curtain walls were created for military purposes. However, after the growth of technology, construction builders began utilizing them for residential and commercial purposes.

Fundamentals

Curtain walls bring many benefits and advantages such as thermal performance, moisture protection, aesthetic, etc. However, they are also classified by their fundamental properties. Knowing these properties can help the building owner in utilizing the most efficient wall system for the facility.

Forms of Curtain Walls

There are three main curtain walls available in the form of rain-screens, face-sealed, water managed and pressure-equalized. The pressure-equalized product is generally the ideal type of curtain wall, which provides higher weathering, air and water infiltration resistance with their unique water-managed systems.

The pressure-equalized wall systems prevent water infiltration across the barrier with their functionality, blocking almost every force that can cause the liquid penetration. PE screen systems are utilized to design the inside surface of the curtain walls, glass or pocket. The airtight barrier of these products is generally created from a wet sealant or an interconnecting gasket

The most effective portion of curtain walls that work as a rain-screen is the exterior glazing materials, outside face of glass, and the frames outer exposed surface, which is made from aluminum plates. Manufacturers form a PE chamber between the interior air barrier and the exterior raining screen in the glazing pocket. This portion reduces the water infiltration by equalizing or eliminating the pressure difference across the panels that tend to push the water inside the buildings structure or the curtain system. However, it is very typical to witness a minor amount of water to penetrate the system, typically wiped to the exterior without causing any damage.

The Water-managed system is almost similar to the PE system at first glance. This system incorporates weeps and drains from glazing pockets. However, there is no effort made to place an air barrier on each glass or spandrel unit. Thus, a more considerable amount of water will infiltrate the aluminum curtain wall system, which should be wiped away. The pressure difference, which is strong enough to force the water to reach a higher position vertically than the internal gaskets, is due to the absence of air barriers resulting in higher leakage. Pockets and holes in this system have high functionality in draining the water that infiltrates the structure.

In contrast, in PE systems, holes function as vents for allowing air movement between the glazing pocket and the exterior wall. The best way to recognize the PE system is to determine that if the pocket around each unit of glass isolated airtight or not. This characteristic can be detected by finding plugs or seals at the gap between screw splines at joint intersections

Some industrial manufacturers prefer to design aluminum curtain walls in face-sealed systems. Their functionality depends on the quality of sealing between the glass units and the aluminum frame or all frames members perform in the application. The long-term usage and reliability of these seals are not safe, and avoiding utilizing them is recommended.

Support of Curtain Walls

They are two types of supporting curtain walls available in the market: stick-framed and unitized systems.

Vertical mullions run pas two floors in the stick-framed systems, usually combined with gravity anchors on the same floor. In some cases, a lateral anchor is used on another floor to increase the support. The splice which exists in between the vertical mullions is designed to provide lateral resistance and vertical movement. In larger scales of this type of support, split vertical mullions are used periodically to provide thermal activity. The glass movement, which takes place within the frame, and the anchors’ involuntary movement tend to persuade additional stresses into the stick-framed method.

Unitized curtain wall systems incorporate the differential movement between the frame’s thermal movement at the joints of each curtain wall and the structure. Due to these products’ customizable characteristics, the amount of action needs to be engineered very precisely. Anchoring and attaching unitized systems involves a proper assembly with three-way dimensional adjustability. There is an existing stack joint in curtain systems that are designed to increase the lateral load resistance, while the two-floor anchors are both utilized for lateral and gravity resistance improvement.

Fire Safety

Curtain walls contain gaps between the floor edges and the back of their structure for slowing down the passage of combustion gases and fire between different levels and floors. For ensuring fire safety, the product must be approved by being tested in fire-rated assemblies. The PFCS needs to be equal to or more significant than the flooring rate. Firefighters who try to extinguish the flame require venting and emergency access, which the curtain walls provide. This specific characteristic is known as a knockout panel. It can be identified by a non-removable reflective dot, which is generally located in the lower corner of the opaque or glass.

Maintenance Access

Curtain walls are designed in a way to provide accessibility for maintenance purposes. Maintaining buildings with low latitude is more comfortable due to the accessibility of equipment that has articulated arms. On the other hand, high-rise buildings need to be designed for swing stage access for general maintenance, repairing, and window cleaning.