4) Classification of shielding systems
To understand the most suitable shielding system, first of all we need to understand the type of radiation that will affect the surface of that building.
A shielding system can be installed on single windows or on the facade of the whole building. Effective shielding must guarantee maximum thermal gain during the winter season and control of solar radiation during the summer. Of course one of the functions to be performed is also to ensure visual and acoustic comfort inside the structure.
Nowadays, shielding systems are often a requirement in the design of buildings with high energy efficiency and low consumption. Technological developments in recent years have led to an ever-increasing range of products available, also thanks to the integration of the screens themselves into the components of the facade of the building in question. In fact, their use is no longer considered only as functional but has acquired a new value also from an aesthetic point of view.
Numerous considerations must be made when designing a shielding system:
- the climatic conditions of the place, to understand how much solar radiation will affect the building;
- the orientation of the building;
- users, type and intended use;
- the height of the building;
- the construction system of the building;
- the characteristics of the materials of the shielding panels;
- the energy flow that affects and therefore the reflection coefficient of the flow obtained by the ratio between the intensity of the reflected radiation and the intensity of the incident radiation;
- the type of shielding.
The types of solar shading on the market are manifold. The legislation shows two categories in particular, but first of all a classification can be made taking into account whether these systems are part of the building or not: that is, if the shielding has the sole task of protecting from the sun or if the function is also the one aesthetic, facade cladding.
A first subdivision of the shielding is given by UNI 8369-4, according to which the systems are divided as follows:
- roller shutter
- Venetian blind
- panel blackout closure
- sun screen
- mosquito net
It can be traced back to four categories of shielding, despite the type of product used: based on the morphology or the shape of the devices, which can be with horizontal or vertical slats, with panels or with a grid, with the position with respect to the closure (internal, external or intermediate), to the fixed or mobile movement, and to the lying plane with respect to the closure (horizontal, vertical parallel to the facade, vertical orthogonal to the facade, inclined).
The most used of all these types are essentially i panels with slat elements, since they don't need complex support structures and their production is not so elaborate and difficult.
These panels are a versatile and adaptable solution, both thanks to the easy design by experts, and thanks to the fact that they can also be an aesthetic element of the facade.
The panels also belong to this category of panels curtains, subject of many studies and research especially in recent years, especially with regard to their fabrics, handling and exterior appearance. In fact the curtains can be manufactured in different materials, such as fiberglass, pvc, polyester, polyvinyl, all treated in such a way as to obtain the appropriate resistance characteristics.
Today, the use of expanded metal, gratings, nets and wire cloths: these materials have often been considered poor and have never been very exploited, in fact they were used mostly to hide secondary parts of the buildings, but they have become pieces to show and exhibit, to complete and to adorn the appearance of the building itself.
As for the shields divided according to their position with respect to the closure, with respect to the outside, inside and in an intermediate position, the external location is the most used, since it is more performing, since it protects from radiation and therefore from overheating : this in fact identifies the solar radiation before it passes the glass and enters internally in the form of heat.
The internal position is definitely not recommended, since it tends to block the radiation when it has already entered. The intermediate location provides solar shading in the interspace between an outermost and an inner glazed panel, and can be considered an ideal solution, because in this way the system is not exposed to atmospheric agents, but at the same time prohibits diffusion of the heat inside.
Let's move on to fixed and mobile shielding; fixed screens cannot change their position after installation, while mobile screens can tilt at different angles, to prevent the entry of solar radiation, both during the year and during the day. The movement of these screens can be rotating or sliding, horizontal and vertical.
Finally, the last category provides the panels based on the lying plane with respect to the closure; therefore there are horizontal or vertical systems, parallel or orthogonal to the closure, and inclined systems. The horizontal or vertical position depends more on the angle of incidence of solar radiation on the facade: facades facing south are preferable to horizontal shields, while vertical and east shields are recommended in the east and west.
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