Functional layers

Functional layers

The external cladding is the component that most enhances the building’s appearance, protects the structure against atmospheric agents and pollution and contributes to obtaining the required performance in terms of energy savings and comfort.

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Metal loadbearing structure and anchor systems

Components of Granitech ventilated facades’ metal structures fall within three categories: 

  • Fixing brackets and respective thermal spacers 
  •  Continuous components: uprights and cross pieces 
  •  Anchors 

From a structural point of view the components are as follows: 

  • The facade uprights are fixed to the building structure by means of brackets and appropriate anchors 
  •  Any cross pieces are fixed to the uprights by means of slotted holes 
  •  External face tiles are fixed to the structure by means of special mechanical or chemical anchor systems

On a ventilated facade the loadbearing structure enables porcelain tiles to be anchored to the building walls, and therefore has a purely static function. The structure framework consists of integrated metal components, installed to create a standardized facade. Ventilated facade structures are made of aluminum, with steel anchor systems. However, they may also be made entirely of steel, or include some wooden components. Aluminum is chosen mainly due to its excellent ductility, sufficiently high strength/weight ratio and good resistance to atmospheric agents. 

When designing these components, one of the fundamental factors to take into account is the size of the structure, which must be able to withstand any stress on the ventilated facade. The latter depends on the size and weight of the porcelain tiles and wind loading they are exposed to. Other important factors to take into consideration are the local climate conditions of the construction area, building’s characteristics, in particular height, location, exposure to strong wind and/or intense or frequent rainfall, environmental conditions and surrounding buildings.

Metal loadbearing structure and anchor systems

ANCHORING BRACKETS 

Anchoring brackets together with respective spacers are positioned directly on the wall of the building, and anchored to it by mechanical or chemical fixings (chosen depending on the type of masonry wall), to facilitate connection to continuous components. In addition, the brackets transmit wind load and other loads imposed on the facade to the structure. This component, with necessary adjustment systems, also makes it possible to compensate for any out of plumb wall differences. Appropriate plastic spacers are positioned between the wall and brackets in order to prevent potential corrosion caused by contact between metal and concrete, in addition to creating a break to prevent thermal bridging. The depth of the brackets mainly depends on the size of the air gap and construction requirements, while the shape, height and number are determined by incidental loads. 

CONTINUOUS COMPONENTS (UPRIGHTS AND CROSS PIECES) 

These components are different shapes depending on the loads they have to withstand and the intervals between fixing brackets. A necessary break should be provided every 3/6 meters in length, in order to permit movement of the structure due to thermal expansion, without creating additional stress as a result of prevented deformation which could cause sudden failure.

ANCHORS 

These components are used during assembly to anchor porcelain tiles to the continuous components. They are provided with separation and anti-vibration gaskets and are divided into those suitable for visible fixing systems (GHV) and those intended for concealed fixing systems (GHS). In installations with visible fixing, Granitech would normally use anchors painted to match the tile, to significantly reduce the visual impact of these components. On systems using concealed anchors, the tiles are anchored to the cross pieces by means of special clips which permit any necessary adjustment. These clips are fixed to the rear of the tiles, using controlled expansion mechanical inserts in special truncated-tapered holes carried out in the factory. Connection between the various components is designed to allow for expansion of each of the components, due to different expansion coefficients. Installed individually and interconnected, through slotted fixings, this allows linear movement without causing damage to the structure or external face. 

Ventilated air gap

In addition to protecting the wall itself and providing a chamber for rainfall, in a ventilated facade the air gap between the insulation and the external tiled face generates air circulation. Air enters at the base of the facade and exits at the top, following the rise in temperature. Solar radiation on the facade and heat coming from living areas heat the air, resulting in subsequent air circulation (chimney effect). Ventilation openings can be protected by grilles, in order to prevent the entry of foreign bodies. To ensure adequate ventilation and generate a chimney effect, the size of the air cavity is particularly important and may vary depending on different components. Functionality of this layer depends on internal air circulation, therefore it should be kept free of any obstacles which may limit this flow, including for example narrowing due to the presence of structural components. 

A ventilated air gap provides a series of benefits and advantages: 

  • Evaporation of any humidity present in the building wall 
  • Extraction of water vapor from internal rooms 
  • Removal of heat due to rising air 
  • Reduced heat flow from the outside to the inside of the building

Insulation layer

An insulating layer is installed to protect the wall and consists of rigid or semi-rigid panels made of vegetable or mineral fibers, or cellular plastic. These components are fixed directly to the supporting wall, by means of suitable fixings. Their thickness varies depending on the material used and the project’s thermal requirements. Installing an insulating layer (if it covers all the structural components) ensures a more even temperature over the entire wall and eliminates so-called “thermal bridges” which are often responsible for creating mold and condensation. 

In addition to specific design requirements, the choice of insulating panel depends in particular on the following performance requirements: 

  • Thermal insulation capacity 
  • Water repellency 
  • Fire resistance 
  • Breathability (to prevent condensation) 
  • Acoustic insulation 
  • Surface color (sometimes necessary to ensure a uniform appearance on ventilated facades with joints that may expose the insulating layer) 
  • Long term resistance to degradation and wear

Back-up wall

The supporting wall for a ventilated facade should be constructed in such a manner as to enable anchoring of the facade’s loadbearing structure and ensure appropriate resistance to wind loads transmitted through the structure. The external surface of the supporting wall, should generally be graded by applying an evenly distributed layer of plaster in order to reduce localized surface irregularities.

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