Features, benefits and design criteria of the ventilated facade: the system that enhances the thermal comfort of buildings
The most characteristic element of a building’s exterior appearance is its facade. Beyond its decorative and connotative aspects, the facade also serves as a dynamic interface between the interior and exterior, a “skin” that regulates heat, air and light exchanges. Influencing the comfort of occupants and the energy efficiency of the entire architectural volume.
The use of ventilated facade is among the most innovative and effective solutions for managing these parameters. If designed with care and expertise, this system proves to be a valuable ally for energy savings, sound insulation, durability and aesthetic enhancement of the building. But what are the principles that govern the operation of ventilated facades? And what materials should be chosen to ensure excellent performance over time?
In this article, we will explore in detail the operation and benefits of the ventilated facade, highlighting the key features that make it an increasingly appreciated element in the design of contemporary buildings.
What is a Ventilated Facade?
The ventilated facade is an advanced system for the external cladding of buildings, made of different materials and installed dry. This innovative approach aims not only to improve thermal and energy performance but also to enhance the aesthetic value of the architectural envelope. Essential for both new constructions and redevelopment projects, a ventilated facade involves the creation of multiple layers, including an air gap that extends between the building’s perimeter wall and the externally mounted cladding on guides.
The technological package of a ventilated facade requires that the outermost finishing layer be slightly detached from the supporting structure to create an aerated cavity across the entire facade surface, allowing air to circulate from bottom to top. Another layer of thermal and acoustic insulation, adhering to the construction, completes the package.
How Does the Ventilated Facade Work?
As effective as it is, the operating principle of the ventilated facade is quite simple and relies on the air convection currents. In simple terms, convection is the movement of air generated in response to temperature variations within the cavity created between the external cladding and the main building envelope. In this case, the outermost finishing layer is positioned at a certain distance from the primary envelope, allowing cooler air to enter the cavity from below and naturally flow upward. An insulating layer is added inside the cavity to enhance its performance.
The finishing layer is independent of the main wall and anchored to it by specific anchoring and suspension systems, which can be visible or hidden. These devices aim to distance the finishing layer from the wall, creating the right size of the cavity and simultaneously supporting it.
Depending on the type of ventilated facade, vertical supports and horizontal crosspieces or brackets are used, generally made of steel, aluminum or other lightweight alloys. In some cases, especially in smaller buildings and in the field of green building, the anchoring system may be made of wood. The cavity usually has a width between 3 and 5 cm, without internal obstacles that could impede airflow. Ventilation grilles are positioned at the base and top of the facade to prevent the settlement of small animals and the deposition of hard-to-remove materials.
The operation of a ventilated facade is, therefore, based on the natural movement of air that develops within the cavity, exploiting a convective flow generated by the temperature difference between the interior and exterior of the cavity.
In the summer, the rise in air temperature inside the cavity, caused by solar radiation on the cladding, creates a “chimney effect” that moves the air upward. This process helps to expel heat, thereby reducing the temperature on the internal wall.
This natural air circulation, known as the “chimney effect,” helps regulate the internal temperature of the building while acting as a deterrent against humidity.
During the winter months, when solar radiation is less intense, the cavity serves as an additional insulation layer and maintains the internal temperature of the wall in balance, also reducing issues related to humidity and surface condensation. To optimize the winter behavior of the ventilated facade, it would be advisable to leave the ventilation grille at the bottom of the facade open, closing the airflow at the top. This way, the continuous air outflow would be interrupted, but the insulating properties of the cavity would increase significantly.
Ventilated facades are particularly effective due to these features. Which, combined with the architectural flexibility they offer, make this technology increasingly popular in contemporary architecture.
For the realization of ventilated facades, both natural and mechanical or controlled ventilation can be adopted. The choice between the two approaches depends on various factors, including the local climate, the size of the building and the available budget.
Natural ventilation, more common than controlled ventilation, rely solely on the physical behavior of air in passive conditions. It uses convective motions: warm, lighter air rises and exits through specific exhaust openings, while cold air enters from below. This approach is economical and requires less maintenance but may be less effective in certain climatic conditions.
If you are interested in this topic, you can also read “How does ventilated roofing work.”
Mechanical ventilation involves the use of forced ventilation devices that ensure a constant and controlled airflow. Although more expensive and requiring more frequent maintenance, it offers greater precision and efficiency.
Material Layering of a Ventilated Facade
The material layering of a ventilated facade is the determining factor in its effectiveness. It usually includes:
- Main vertical envelope (brick, concrete blocks, etc.);
- Supporting structure (aluminum, wood, steel, or other alloys);
- Thermal insulation layer;
- Ventilation space;
- External cladding (brick, ceramic, aluminum, etc.).
These layers, if integrated synergistically, can significantly improve the thermal and acoustic performance of the entire building.
Here are some tips to follow for sizing the various layers.
To function correctly, the air cavity of a ventilated wall should not have a thickness less than 2 cm.
Its sizing is based on a mathematical ratio between the width of the facade to be clad and the desired ventilation type (weak or strong). Also considering the thermal resistance of the cavity based on the airflow on the facade. The thickness of the cavity should be carefully evaluated based on the height of the facade. Ensuring the continuous airflow from bottom to top. Only the right proportion between thickness and height will ensure the chimney effect. And therefore, the facade’s ventilation.
The thickness of a finished package, including all components of the vertical envelope, can easily exceed 40 cm, depending on the external cladding, cavity, insulation, etc. When it is desired to make the void through which air circulates inspectable (to allow the passage of maintenance personnel), the final package can have significant thicknesses, even exceeding 90 cm.
To calculate the thickness of all layers of the ventilated facade so that the entire closure package complies with the values specified by regulations (transmittance, thermal resistance, etc.) for each climatic area, it is necessary to use energy analysis software. Only in this way can you be sure of the efficiency of the adopted design choices and compliance with all regulatory constraints.
The ventilated facade benefits range from energy savings to aesthetic improvements. Among the main advantages:
- Energy efficiency: reduced energy consumption thanks to thermal control and natural or mechanical ventilation;
- Sound insulation: the air cavity acts as an effective sound insulator, reducing sound transmission;
- Structural protection: the material layering contributes to protecting the building structure from moisture, weather conditions and climatic variations;
- Aesthetic enhancement: a wide range of materials and designs give the building a modern and distinctive appearance;
- Durability and cost savings on maintenance: there is no need to redo the facade, repaint, or restore the finishing layer. The cladding materials are much more durable than the common plaster used in traditional facades. This also leads to long-term cost savings as there are no significant maintenance expenses to consider over time.