Building envelope that is, almost literally what delimits a building or a structure and becomes a “mediator” between what is inside and what is outside. It separates and connects at the same time, or rather, depending on what is convenient, to the inhabitants or users of the building in question.
For building envelope means the set of all technological units and technical elements that appear as an internal / external limit, in a "morphological" but also "functional" sense. Usually we talk about dry building envelope, and thus it is understood that everything of which it is made up, technological units and technical elements, is held together by “dry” anchoring systems. To be clear: bolts, screws and welds. Or dry joints.
Building envelope and energy saving
Over time thebuilding envelope it has become increasingly the object of attention, especially for what it has been, is and will be its relations with the structural and plant systems.
In the past, the distant past, the idea was to stay in balance with nature by focusing on the recycling of materials, also recycling buildings for new purposes of use, but using as little new materials as possible. In the 70s humanity got the "anxiety" ofthermal insulation, realizing the consequent economic and environmental benefits, so we began to develop envelope insulation techniques.
Here then are new materials and above all a change of concept. L'building envelope from a simple protective barrier-element it began to be conceived and designed as a complex filter system. If well designed, it can also optimize interactions between exterior and interior.
Gradually, with the evolution of studies and our awareness of the importance ofbuilding envelope, we began to focus on varying its performance according to external environmental situations and, obviously, to the needs of those who live inside thebuilding envelope. With this step, various devices are therefore assembled therein, different from the elements seen so far and aimed at exploiting the natural resources to produce energy.
Sustainable building envelope
By intelligently interacting with the external environment, thebuilding envelope becomes sustainable. Active or passive. If passive, the building envelope limits itself to maximizing direct solar gain, showing the world, the sternum, the largest possible glass surfaces like a dazzling smile. In addition to these sun catchers, thepassive envelope it can also be equipped with greenhouses to capture solar energy in winter and with devices to let sunlight into the interior, also taking advantage of some natural ventilation. Quant is enough, as much as you wish.
The building envelope becomes active when it is enriched with systems for the collection and transformation of solar energy and for artificial ventilation from the outside. Obviously this second type is more efficient in energy terms, we can benefit more from it but not without having to make sacrifices. And in this case it is a sacrifice of architectural castration: thebuilding envelope active, in order to be active it places limits on the creativity of those who design it, who find themselves having to deal with often rigid modules and “rules” that make the internal distribution of the environments schematic and limited.
A good compromise in this situation can be reached with a active building envelope consisting of a ventilated glass wall: these are two transparent surfaces separated by a gap and artificially ventilated through air vents. Another idea is to integrate a photovoltaic system into the facade by making the cells appear here and there on the glass walls.
Innovative building envelope
Innovative, but to what extent convenient? It is the hybrid building envelope. The architects have developed it, some, with many expectations, convinced that they can obtain the optimal synthesis between passive and active. Yes, they wanted a building envelope that was both passive and active, that is to say capable of performing different functions above all of changing its performance from time to time looking “out the window” at the time ago. To date, this innovation requires very high costs, both for construction and maintenance
Energy efficiency of the building envelope
To understand if a building envelope it is energy efficient, it is necessary to evaluate its ability to react flexibly to changes in weather. To be a good building envelope, it must be able to minimize heat loss in the winter and limit spikes in summer heat. If so, everything goes for the benefit of the comfort of those who live inside the building envelope, but also for the benefit of the environment, because it feels good at home and no non-renewable energy sources have been used.
Building envelope: a complex design
It is not all in one piece, there'building envelope, although so far we have talked about it as a homogeneous entity. It is actually made up of elements and layers. There is the load-bearing element, and then the anchoring element that holds the coatings. Here the complexity of the choice is there: it is necessary to evaluate according to the type of surface, the accidental and permanent loads and the measures and distances as well as from global support structure. Finally, there is the infill and external covering layer.
Technologies and modern architecture allow a wide range of action, and allow us to indulge ourselves. The aim is to guess among the many combinations the one that exploits them with style potential synergies between different materials and integrates multiple building and housing systems. Two lines to say it, but to do it ...
Building envelope: types
As for the construction system, the types of building envelope dry are generally three. There are the structures made up of uprights and transoms, there is the evolved version of these - the structures made up of uprights, transoms and external screens - and then there are the cell or unit structure.
This is a schematic distinction that does not take into account how, with the evolution of the systems of building envelope, both the complexity and the quality of the structures designed and built have actually increased, also “playing” on different materials used for the coating layers. Let's see some examples of the facade. After all, if we are not architects, with respect to the rest of thebuilding envelope, but it is what we laymen catch the eye.
There curtain wall or curtain wall it is mainly made of metal, wood or PVC, showing vertical and horizontal structural elements connected together. The effect of the cladding is one of continuity of the envelope with respect to the load-bearing structure of the building, which remains entirely set back from the plane of the facade.
When the facade of thebuilding envelope it is ventilated, on the other hand, there is a screen in which the gap between the cladding and the wall is designed so that the air can flow due to the chimney effect according to seasonal needs. It is very clever as a facade and improves on overall thermo-energy performance of the building envelope. And everything about the building.
Less common but worthy of mention are the a structures Rain Screen Cladding, aimed at protecting from driving rain and damp infiltrations. And then the double skin façade: you can see a transparent container along the entire perimeter of the building formed by an external, fixed skin to protect the building from the elements, and then the internal one, often with fixtures to ventilate the internal rooms
Integrated building envelope
This is the case in which thebuilding envelope it starts to produce energy. Here then appear photovoltaic panels that transform solar radiation into electricity. Or solar shading, such as fixed, mobile and adjustable sunshades. L'interactive building envelopemoreover, it looks around and knows how to evaluate climatic variations through automatic control devices or through direct user intervention.
In this way it can then check the performance levels of thebuilding envelope acting on any closures and thus modifying the values of thermohygrometric and environmental parameters related to the internal microclimate.
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