A Curtain wall is a non-structural cladding system for the exterior walls of the building. It is a thin aluminium framed wall containing infills of glass, metal panels or thin stones. It separates the interior from the exterior, supporting only their own weight and transfers rest of the load (wind and gravity) back to the primary structure of the building. Post and beam and balloon framed timber structures effectively had an early version of curtain walls, as their frames supported loads that allowed the walls themselves to serve other functions, such as keeping weather out and allowing light in. Some of the first curtain walls were made with steel mullions, and the polished plate glass was attached to the mullions with asbestos- or fiberglass-modified glazing compound. Eventually silicone sealants or glazing tape were substituted for the glazing compound.
Curtain walls are used to resist air and water infiltration, and to also resist the sway induced by wind and seismic forces acting upon the building. It possesses structural importance equal to the other elements of the construction. 
Curtain walls perform two prominent functions – 
•    Acts as a weather barrier 
•    Allows light to enter the interiors
Due to being exposed to exterior atmosphere, the maintenance and installation process should be adequately done to ensure proper functioning. 
COMPONENTS OF A CURTAIN WALL SYSTEM
•    Transom
•    Mullion
•    Vision glass 
•    Anchor

 TYPES OF CURTAIN WALL SYSTEM
 Stick curtain wall system –
    In this type the components are required to be assembled piece by piece on the building. 
    It is mainly used as installation for low rise buildings. The vast majority of ground to floor walls are installed as sticks here.
    The benefits of this system is lower shipping costs and flexibility in making possible adjustments on site.
  Unitized curtain wall system – 
    It involves assembling by the means of interlocking units that are bought from the factory. 
    The components are bought together as a single until from the factory to the site. 
    The completed units are installed on the structure to form enclosure.
    The size of the unitized curtain walls is dependent on floor to floor height.
    They are popularly used in high rise buildings, don’t need extra support such as crane or scaffolding.
    One of the drawback is increased shipping charges due to need to provide protection during transportation.

CATEGORIES OF CURTAIN WALL SYSTEM:

SPIDER curtain wall – Provides maximum daylight into the interiors due to use of huge transparent glass, a widely accepted trend for commercial structures.

RUBBER curtain wall – They are mainly rubber strip on the walls, that can be shaped and designed into customized form and pattern.

FIBERGLASS curtain wall – They expand usable areas and have excellent thermal performance providing comfortable space.

PHOTOVALTIC curtain wall – Generated electricity with the help of solar energy and provides energy efficiency

GLASS curtain wall – they are comparatively light weighted than other available options and need less cleaning maintenance for long period of time. Aluminium frame walls and metal panels are used to attach this glass to the structure.

TIMBER curtain wall – It is widely used in high end residential, hospitality complexes in conjunction with hardwood. 

PVC curtain wall – One of the lesser expensive and easy to install options available in the market. Provides a longer life shelf as it does not break easily. 

Curtain walls balance conditions along the envelope to control thermal expansion, movement, cooling and lighting. It is important to consider the support of curtain walls and how they transfer loads to floor structure and framing. The following projects are examples that illustrate different framing and installation systems

Kent State Center for Architecture and Environmental Design by WEISS / MANFREDI, Kent, OH, United States
Created with a continuous gallery that anchors the building’s main public level, the new Kent State Center opens up to its surroundings while elevating space for design. Continuous sightlines combine with large curtain walls that encourage interdisciplinary discourse and enhance a sense of peripheral vision for students and faculty.

 

Vol Walker Hall and the Steven L. Anderson Design Center by Marlon Blackwell Architect,
The project features more than 17 different glass make-ups in a wide array of system types, including: 6,000 square feet of the Kawneer 1600 System 2 veneer structurally glazed curtain wall with 140 vertical glass fins made with Viracon V175 silkscreened glass.

 

 Davis-Harrington Welcome Center by Dake Wells Architecture, Springfield, Mo., United States
 The rear ground-floor spaces are wrapped behind limestone cladding; to the north, the envelope has greater transparency,  culminating in a tapering glass curtain wall that accentuates the building’s main entrance.