Design, Environmental Compatibility, Emphasis On Structure
The external cladding of buildings plays a crucial role in contemporary architecture and in the qualifi cation of the urban landscape, as well as having the important function of protection against weathering. The design of urban spaces therefore requires reconciling aesthetic requirements with needs related to the durability of the different elements, environmental compatibility and economic sustainability in relation to the entire lifespan of the space designed. In particular, the exterior surfaces of buildings are subject to numerous types of stress: mechanical, chemical, thermal, and hygrometric, stress related to human activity, the quality of the air, and weathering. These surfaces play an important role in both the aesthetic impact of the building and its integration into the surrounding landscape, and the materials must match the need for protecting the environment and for sustainable development.
With a state-of-the-art production of high-tech materials for fl oors and walls, Ariostea offers its experience in the design and production of claddings for large exterior surfaces. Ariostea technical staff can develop both traditional and complex construction systems for claddings, giving designers and architects the greatest freedom in the creation of enclosures that both protect the building and enhance the architectural structure. With their rich array of colours and surfaces, Ariostea high-tech marble and stone offer enormous design fl exibility, guaranteeing superior aesthetic results and excellent technical features in terms of durability, easy installation, and reduced maintenance.
The ventilated facade system is currently the most complete synthesis of the characteristics that exterior walls must have in order to ensure well-being inside a building. The primary function of the system is indeed to protect the building from weathering and particularly from the infi ltration of rainwater into the building walls, which is the main cause of deterioration. Spacing out the cladding slabs from the wall also creates a ventilated air gap which, combined with the action of an insulating layer applied on the building walls, considerably improves the building’s thermal effi ciency. Further important advantages of the system include the dispersion of water vapour through the walls, the improvement of soundproofi ng as well as the reduction of maintenance operations and the possibility to punt some fi ttings outside the building. The fl exibility of the system lends itself to both new building construction and the renovation of old buildings. This system is an excellent means for the latter, as it helps improving the quality of the existing building. Also in terms of composition, the ventilated facade offers new expressive possibilities by mixing and matching of different
The Construction System
The ventilated wall is a complex construction system developed in accordance with industrial design criteria. Every detail must be examined and defi ned in advance to avoid the need for substantial modifi cations while the works are already in progress. The system is anchored to the building walls, which act as the support, and involves "superimposed" layers comprising:
- the insulating blanket
- the load-bearing steel construction structure
- the facing elements
Between the insulation and the facing, an air gap is thus created which, by means of a "chimney effect", sets up effective natural ventilation, ensuring signifi cant benefi ts related to the removal of heat and moisture.
The perimeter wall of a building must ensure suitable anchoring of the load-bearing structure of the ventilated facade, and must be made of materials (masonry, reinforced concrete, blocks) and systems that ensure suitable resistance to the wind loads allowed for in the design project. A suitable choice of the thickness and type of support material, along with the advantages offered by the ventilated wall in terms of thermal performance, eliminates the need for the traditional inner counterwall made of hollow bricks, thus providing useful surface for housing. Attention must always be given, however, when positioning wiring and cabling in the walls, so that these do not interfere with the anchoring of the facade covering. To reduce any irregularities in the underlying wall, it is advisable to spread a layer of mortar uniformly over the external surface of the support.
The insulating blanket is composed of thermal insulating material of variable thickness depending on the material used and the thermal requirements of the design project. It is anchored directly to walls using mechanical bolts. Mechanical anchoring of the blanket is particularly indicated for facade repairs, as adhesives may not be able to guarantee perfect adhesion on surfaces that are irregular and have deteriorated due to exposure to weathering. The insulating blanket must be composed of semi-rigid or rigid panels in mineral fi bres or cellular materials. The choice of the insulating material depends on the following performance requirements:
- thermal insulation capacity
- waterproofi ng
- non-fl ammability
- colouring of the surface layer (in some cases the size of the joints between the facing elements might expose the insulating layer).
Ventilated Air Gap
The air gap between the insulation and the external facing must be suitably sized to guarantee good air circulation and, above all, to set up the "chimney effect" (upward draught of warm air). It is usually between 30 and 80 mm thick. The functionality of this gap depends on its internal air circulation conditions, so it should be kept free of any impediments that might limit the fl ow (bottlenecks caused by the presence of structural or anchoring elements, surface irregularities of the insulating layer or facing material, etc.). To enable the upward movement of the air inside the gap, ventilation openings of adequate size must be put at the bottom and the top, where necessary with protective grates to prevent the entry of foreign bodies. The presence of a ventilated air gap means:
- the evacuation of water vapour coming from inside the building
- the heat removal by the upward motion of the air
- reduction of the heat fl ow from the outside to the inside of the building.
The load-bearing structure consists of integrated metal elements, generally extruded aluminium profi les, including brackets, uprights, crosspieces, and anchoring devices, which are assembled in such a way as to obtain the necessary modularity of the facade. The small metal accessories for anchoring the facing slabs, with gaskets to separate the elements and prevent vibrations, are either inserted into the extruded aluminium profi les or riveted to them. The load-bearing structure works as follows:
- the uprights of the facade are anchored to the building structure by brackets and suitable bolts;
- any crosspieces (used only in certain systems) are anchored to the uprights through slotted holes;
- the facing slabs are anchored to the uprights using special metal accessories.
The connections between the anchoring brackets and the uprights, as well as those between the uprights and the crosspieces, are made using rivets, transmitting the weight of each element and related facing slab to the building structure. The brackets also transmit wind loads and other stresses that the structure has to bear. The anchoring system is designed to compensate for the dimensional differences of the building structure in the three orthogonal directions. By modifying the design of the anchoring system, where necessary the facade system can be designed with higher tolerance absorption than the building structures. The connection between the various elements is designed to permit the expansion of each component. Components with different expansion coeffi cients are separated and connected using slot anchors that allow the respective movements. These joints are sized so as to absorb the movements without any damage to the structure, and the gaskets reduce the friction between the elements.