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A Brief Discussion on Double-skin Facade System

The concept of building design has evolved significantly over the years to meet the ever-changing demands for function, comfort, and energy efficiency.  This evolution has resulted in significant innovation in the design space, from integrating smarter design elements to using a new range of materials. Double-skin façade system is one such innovation. In most instances, these systems comprise of traditional façade systems combined with an additional outer layer that covers the building partially or completely.

As human beings, we stay warm during the winter by wearing multiple layers of clothing to insulate the body. Architects make use of the same principle to keep a building warm or cool. Here, the exterior wall of a building can be considered to be similar to the human skin.

A building’s exterior wall serves as the barrier between the interior and exterior of the building, and is referred to as a façade. A passive façade is the one that deals with the cooling and heating issues naturally. On the other hand, an active façade influences the interior climate of the building by integrating different digital and mechanical systems or devices.

Also known as DSF, double-skin façade is a building envelope comprised of two transparent skins separated by a corridor of air. This is a form of active façade as it employs solar sensors, fans, etc. DSF systems also integrate passive design strategies like daylighting, natural ventilation, and solar energy. Therefore, it can also be considered to be a hybrid that utilises both natural as well as mechanical energy.

Double-skin Facade System and Material:

A double-skin façade system can be created covering just a part of the façade or over the entire façade. Applicable to all types of buildings, it is possible to install DSFs to all existing buildings with very little adjustment.

An exterior wall, an interior wall, and a ventilated cavity are the three components of a DSF system. The exterior wall’s function is to protect the building against unfavorable weather conditions. In most instances, this wall is made of a single layer of laminated safety glass or heat-strengthened safety glass. High-reflective flint glass is also used sometimes for more transparency. It has also been observed that some architects prefer using spectrally-selective glazing because it prevents solar heat transmission while allowing the daylight.

Structurally speaking, the interior wall of a DSF system is a double or single pane glass with thermal insulation property. Low-emittance coatings are often used here for reducing radiative heat gain. This façade component may also have hopper windows, operable casement, or sliding glass doors.

The cavity in the DSF system is a divided or undivided buffer space with width ranging between five and fifty inches. Some DSF cavities have grills or metal floors at each level, allowing easy access for cleaning, maintenance, and fire escape. The function of this cavity is to insulate the building against temperature, sound, and wind.  The outside air is pulled in by the cavity, and is used for the controlled ventilation of the building’s interior areas. Within the cavity, the ventilation can be fan-assisted, mechanical, natural, or automated by a computer.

The intermediate space in the DSF system is also used for solar protection. Moreover, cavity is the place where we find shading devices such as roller shades, blinds, motorized openings, louvre systems, or fans. Louvres are mostly made of glass, but perforated sheets, aluminium profiles, or fabric coverings are also used.

Types of Double-skin Façade:

Double-skin facades can be divided into four categories as discussed below.

  • Buffer DSF System: These systems are designed to maintain sufficient daylight in the building while increasing the wall system’s insulating properties. They utilise two single glazing layers placed 250mm-900mm apart. Buffer DSF systems allow fresh air into the building interior in a controlled manner through a box type window or HVAC system.
  • Extract Air DSF System: These systems contain a second glazing layer at the interior of the main double glazing façade. As a result, the space within the two glazing layers becomes a part of the HVAC system. Fans are used to extract the heated used air from the space between the glazed layers. Heat-transmission loss is minimised by an outer layer of insulating glass. These systems are used mostly in areas with high wind, noise, and fumes and in places where natural ventilation is not possible.
  • Twin Faced DSF System: These systems comprise of conventional thermal mass or curtain wall system within a building skin with single glaze. Laminated, safety glass or insulating glass is used as the outer glass. An interior space of minimum 500mm-600mm is required for cleaning these systems. It differs from buffer and extract air systems due to the presence of an opening for natural ventilation.
  • Hybrid DSF System: Hybrid DSF systems are the combination of any two of the DSF systems discussed above. A hybrid system is used when none of the other three systems can be accommodated to a building system.

Advantages of Double-skin Facade System:

Improved Energy Efficiency: During the winter, DSF systems preheat the air in the cavity using solar rays. The heating demand is reduced significantly by thermal insulation, which is extremely useful in cold climates. It also provides protection from excessive sun during summer as the shading devices restrict the sunlight.

Natural ventilation: Double-skin facades have ventilation properties that can help significantly in keeping the interior of the building and the occupants cooler. This reduces the dependence of the occupants on air-conditioning units.

Acoustic insulation: Sound insulation efficiency of DSF units can be increased to a great extent by using perforated metals in the proper manner.

Occupant comfort: With excellent temperature control and superior ventilation, human comfort in undoubtedly one of the reasons behind the growing popularity of DSF systems.

If you have any further questions about double-skin facades, please contact us at CGS Façade Group. Our team has a wealth of experience in dealing with all the latest advances in the field of building envelope systems.