A 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 a 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. The curtain wall façade does not carry any dead load weight from the building other than its own dead load weight. The wall transfers horizontal wind loads that are incident upon it to the main building structure through connections at floors or columns of 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, although the first curtain walls were made of steel. The aluminium frame is typically infilled with glass, which provides an architecturally pleasing building, as well as benefits such as daylighting. However, parameters related to solar gain control such as thermal comfort and visual comfort are more difficult to control when using highly-glazed curtain walls. Other common infills include: stone veneer, metal panels, louvres, and operable windows or vents.
Aluminium cladding enables architects to incorporate visually desirable features into building design. On building exteriors, aluminium cladded sheets, shingles, and pre-fabricated panels can be cut, routed, sawed, filed, drilled, screwed, welded, and curved to form complex shapes. A variety of finishes and colors are available. For description of alumunium facade cladding systems, see: aluminium in architecture: wall cladding. 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, and lighting in the building.
Systems and Principles
The vast majority of curtain walls are installed long pieces (referred to as sticks) between floors vertically and between vertical members horizontally. Framing members may be fabricated in a shop, but all installation and glazing is typically performed at the jobsite.
Unitized curtain walls entail factory fabrication and assembly of panels and may include factory glazing. These completed units are hung on the building structure to form the building enclosure. Unitized curtain wall has the advantages of: speed; lower field installation costs; and quality control within an interior climate controlled environment. The economic benefits are typically realized on large projects or in areas of high field labor rates.
A common feature in curtain wall technology, the rainscreen principle theorizes that equilibrium of air pressure between the outside and inside of the "rainscreen" prevents water penetration into the building itself. For example the glass is captured between an inner and an outer gasket in a space called the glazing rebate. The glazing rebate is ventilated to the exterior so that the pressure on the inner and outer sides of the exterior gasket is the same. When the pressure is equal across this gasket water cannot be drawn through joints or defects in the gasket.
Aluminium Composite Panel (ACP) also Aluminium Composite Material, (ACM) is a type of flat panel that consists of two thin aluminium sheets binded to a non-aluminium core. ACPs are frequently used for external cladding of buildings (building facades), for insulation and for signage.
Aluminium sheets can be coated with PVDF or Polyester paint, making ACP very rigid and strong despite its light weight. Aluminium can be painted in any kind of colour, and ACPs are produced in a wide range of metallic and non-metallic colours as well as patterns that imitate other materials, such as wood or marble. The core is commonly low density Polyethylene, an insulating material no less than 10 cm thick when its use is refrigeration insulation, or a mix of low density polyethylene and mineral material to exhibit fire retardant properties.
ACP is mainly used for external and internal architectural cladding or partitions, false ceilings, signage, machine coverings, container construction etc. Applications of ACP are not limited to external building cladding, but can also be used in any form of cladding such as partitions, false ceilings etc. ACP is also widely used within the signage industry as an alternative to heavier, more expensive substrates.
ACP has been used as a light-weight but very sturdy material in construction, particularly for transient structures like trade show booths and similar temporary elements. It has recently also been adopted as a backing material for mounting fine art photography, often with an acrylic finish using processes like Diasec or other face-mounting techniques. ACP material has been used in famous structures as Spaceship Earth, VanDusen Botanical Garden, The Leipzig branch of the German National Library.
These structures made optimal use of ACP through its cost, durability and efficiency. Its flexibility, low weight and easy forming and processing allow for innovative design with increased rigidity and durability.
Many people use dibond or sandwich panel as a generic name (genericized trademark) for aluminum composite panels that are 0.3 mm thick aluminum sheets covering a solid polyethylene core with a total thickness of 3 mm, or similar panels from any manufacturer.
A variety of manufacturers sell aluminium composite panels under a wide variety of brand names, including (in no particular order)
Dibond from 3A Composites and Alcan, Max-Metal from Grimco, Reynobond from Alcoa, RedBond from RedBond Composites, Alucobond from 3A Composites, Plascore Board from Plascore, Alupanel from Multipanel UK, Hylite from 3A Composites, Etalbond from Elval Colour, Larson from Alucoil, etc.
Some people use sandwich panel for any structural sandwich (sandwich-structured composite) of a core bonded between two cover sheets, no matter what material(s) it is made of, and no matter if the core is solid, foam, flutes, or honeycomb.