Ventilated walls

1. Technological aspects related to energy efficiency in ventilated walls.
1a. Climatic efficiency in the summer and winter
1b. External insulation and soundproofing
1.c A way to reduce the energetic and environmental costs of air conditioning.
2. Solutions to engineering problems that used to cause uneven results.
2a. The ceramic materials employed
2b. Testing and certifications
2c. Dealing with rain
2d. Project success based on the synergy between professional skills.

1.Technological aspects related to energy efficiency in ventilated walls.
Marazzi Engineering can now rely on over 15 years' experience in the field of ventilated walls: specifically, ventilated facades with an outer cladding of ceramic slabs.
This is a material that has long been suited to such applications, but which has considerably evolved in recent years in terms of both technology and tile sizes, with an increasingly broad, diverse range of styles and surfaces that has increased the available selection and greatly boosted the popularity of these curtain walls.
Enormous effort has been made to familiarize designers and potential clients not only with "lightweight" ventilated walls, but also with “light” versions faced in ceramic, which up to now was considered a material for interior use, suited at best to balconies and outdoor walkways, but not to major technological and architectural applications such as the outer cladding of buildings.
The fact that we can now analyze and compare the positive results of projects carried out in Siberia or in other cold countries, or in Africa - even in areas near deserts with famously inhospitable climates - makes it easy to grasp how well ventilated walls perform the tasks they are designed for, especially in terms of energy savings.
When we talk about ventilated walls, what we mean, first and foremost, is a thermal integration system composed of a continuous layer of insulation applied to the outside of the building's perimeter, and an external cladding supported by a metal structure.
The air gap between the insulation and the outer envelope creates a chimney effect, or at least an upward current of air.
The effectiveness of this system has been proven through concrete thermal transmission and energy parameter optimization tests performed on various types of external walls; the ventilated system outperforms traditional envelopes using the same materials by up to 20%. The air space definitely offers considerable advantages. The joints between cladding units are usually open, and there is particular ventilation in the space surrounding each slab.

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1a. Climatic efficiency in the summer and winter
The system's efficiency depends on various factors: the climate, the local wind load, the thermodynamic characteristics of the outer wall to which the structures are attached, and the building's height and shape, as well as the properties of the outer shell and its permeability to air.
During the summer, the heat reflected by the external shell or channeled away by the upward current of warm air in the air gap is definitely greater than what would enter the building through its outer walls.
During the winter, since the temperature outside is close to the temperature in the air gap, the flow of air is reduced and all the benefits of the external insulation remain.

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1b. External insulation and soundproofing
This is rounded out by the system's correct permeability to water vapor, since the outer walls are remarkably capable of expelling the moisture produced inside, removing all barriers to humidity and thus increasing permeability to its passage from the inside out.
The layer of insulation also increases the soundproofing effect, since it absorbs noise from outside. By comparing the ventilated wall system, where the insulation panel is placed outside the bearing walls, with an equivalent traditional outer wall made from a double layer of bricks and an insulating panel between the two layers, we can see the advantages of the curtain wall, since in this case the insulation is not interrupted by the floors or partition walls, thus eliminating the thermal bridge problem at the root. Layers of rigid insulation can also be placed under the ends of the supports for the metal substructure at the points where they are attached to the wall, to eliminate other thermal bridges.
The external position of the insulation layer plays a fundamental role in overcoming the problem of interstitial condensation, especially when accompanied by good ventilation.
The insulation is usually fiberglass or rockwool, and the thickness and density of the pads are a factor in the energy engineering of the curtain wall.
The considerations that regard heating also apply to air conditioning.

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1.c A way to reduce the energetic and environmental costs of air conditioning.
Air-conditioned buildings are becoming more and more common, entailing considerable use of energy; for example, in the United States, air conditioning accounts for approximately 16% of power consumption and is responsible for 43% of load peaks. Air conditioning needs are one of the primary factors in energy demand.
Global warming aside, one must acknowledge that Italy also seems to be heading in the same direction, and while a heating system is always included in the building design, the air conditioning system is often added later, when many parts of the design have already been established, and this can often conflict with other building engineering factors.
The architectural and technical benefits of ventilated walls can be helpful in this sense as well.

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2. Solutions to engineering problems that used to cause uneven results.
The solution, or at least the best path to resolving problems, is a serious approach to the design of the ventilated wall.
This is a winning strategy for companies who even offer turnkey packages that include the working design, the outer cladding material, the bearing structure, and erection of the curtain wall.
Turning once more to the ceramics sector, which has arrived in this field only recently but with flattering results, one can see that many leading firms have set up engineering divisions to engineer, produce, and put together the various stages of the project.

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2a. The ceramic materials employed
Nowadays, ceramic materials come with standard features already suited to ventilated wall applications: porcelain stoneware is at the top of this sector, due to its total frostproofing, low absorption, high modulus of rupture even in thin tiles, and excellent resistance to atmospheric pollution: its eco-compatibility can be immediately seen, but companies certify its quality by meeting specific quality and production standards.

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2b. Testing and certifications
However - and this is an important point - certifications go beyond those regarding only the ceramic material used in the external cladding. The systems of interface with the bearing structure are no longer the sloppy, makeshift systems that used to appear and pass out of vogue in a single season.
A primarily mechanical interface between the slab and the structure is now created with various methods of drilling, plugging, or milling, and the entire system is subjected to pull-off tests with omnidirectional forces, vibrations, and temperature shocks, as well as checking how the slab-anchor system functions when one or more attachments or anchors come loose for some reason.
In Germany, the country where ceramic ventilated walls were invented, and where they have recently seen considerable use in new projects and massive use in renovation projects (starting with East Berlin), the entire facade wall system has undergone years of testing: i.e., tests are performed on the cladding once it has been mounted on the specific structure and anchored to the masonry walls. After testing, the system receives a certification (Zulassung) that takes wind loads into consideration according to the standards set by German law, through static and dynamic tests, and this certification must be confirmed every year with an inspection performed by an external technical/scientific institution, checking the materials and the individual consignment and job lots.

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2c. Dealing with rain
There has always been the fear - often justified - that rain could penetrate to the building wall, causing problems with mould and decay; it used to be commonly believed that this was caused by the open joints of the cladding.
Once it became possible to open the shell easily, it would be discovered that poorly mounted insulation - often flaking or obstructing the air circulation channel - was carrying rain towards the wall, as well as losing its thermal characteristics once damp.
Or else the shape of the support beams channeled rain along the brackets attaching them to the external masonry wall.
The most delicate points, however, were at the windows and doors: Unless carefully designed and then properly installed at the construction site, the shape of the frame surrounds - often made of aluminium or ceramic - would cause rainwater to puddle inside them.
Another source of problems was the line of junction between two different types of facade: glass walls next to walls made of ceramic or metal, such as zinc-titanium sheeting or aluminium.
Similarly, the line of junction between a ceramic ventilated wall, running up the entire height of a building, and the wall of the ground floor - perhaps clad in ceramic, but laid with adhesive - would create major problems without a suitable waterproofing system to channel rainwater out of the ventilation grates.

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2d. Project success based on the synergy between professional skills.
Waterproofing, junction points: all simple yet fundamental matters that should not be dealt with on an ad-hoc basis in the construction yard, but rather in the details of the design. The design needs to be based on collaboration between the engineers of the different kinds of facades, along with the door and window specialist, a key figure in these projects.
These details do not complicate the facade, but rather give it a certain uniformity, and become essential during erection and maintenance. It is essential to know what part will be erected first and how it interfaces with the other systems, so that if one day the curtain wall needs to be opened for inspection, one can proceed on a sure footing, at a low cost and with a guaranteed outcome.

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For more technical information about ventilated walls.

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