Ventilated facade: typical stratigraphy, characteristics, and thicknesses

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.

Among the most innovative and effective solutions to optimize these parameters is the ventilated facade, a construction system that is now widespread and highly appreciated for its aesthetic quality, durability, low maintenance, and the great climate comfort it offers. If designed correctly, it can prove to be a valuable ally not only for energy savings and acoustic insulation but also for the protection of the building envelope and architectural enhancement.

But how does a ventilated facade actually work? What materials should be chosen? And above all, how do you design an efficient stratigraphy and correctly size the air gap, a key element to ensure effective convective movements and high performance in all seasons?

In this article, we will explore in detail the functioning and benefits of the ventilated facade, highlighting the key characteristics that make it an increasingly appreciated element in the design of contemporary buildings.

Modular Ventilated Facade

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.

Ventilated wall: typical stratigraphy

Let’s take a closer look at all the layers present in a ventilated wall:

• perimeter wall that serves as the vertical closure of the building and as a load-bearing structure to anchor the supports of the cladding. It can be assembled traditionally (bricks, hollow bricks, etc.) or with dry systems (gypsum board, etc.);
• insulation installed in adherence to the outer perimeter wall, just like in the “thermal coat” system. It can be chosen from different materials such as EPS, wood fibers, etc.;
• air gap, is the layer of air that forms between the insulating layer and the outer cladding;
• external cladding made with various opaque materials (ceramic, stone, aluminum, etc.) or transparent materials like glass.

These 4 layers are structurally connected to each other by:

• metal structure (usually made of aluminum, steel, or other lightweight alloys) that supports the external cladding and anchors it to the outer perimeter wall;
• anchoring system consisting of brackets, profiles, dowels, chemical anchors, screws, bolts, rivets, and brackets, necessary to fix the cladding to the structure and the structure to the outer wall.

Ventilated wall

How to size the ventilated facade: thickness of the air layer

Correctly sizing the air gap is essential to trigger upward convective motions, true air flows that move from the bottom to the top of the facade surface. The air heated by the sun rises through the gap, generating an airflow that helps reduce heat and noise transmission to the interior spaces, as the gap acts as a buffer zone between the outside and the inside of the building.

To determine the sizing of the aeration layer of the ventilated facade, there are several calculation methods. The most commonly used is certainly the method described in Appendix B of UNI EN ISO 6946:2018.

This European technical standard provides specific guidelines for calculating the thickness of the air gap, including the assessment of natural air flows and the analysis of the chimney effect to determine the height of the gap and the optimal dimensions to promote convective motion. This helps ensure that the gap can effectively reduce heat transfer and guarantee effective thermal insulation of the building.

To identify the stratigraphy of the ventilated wall and size the air layer, it is first necessary to establish whether one wants to design a facade:

• weakly ventilated, when the gaps are characterized by limited air passage, coming from the external environment through openings with the following characteristics:
  • ranging from 500 mm² to 1500 mm² per meter of length for vertical air gaps;
  • ranging from 500 mm² to 1500 mm² per square meter of surface for horizontal air gaps;

• strongly ventilated, when ventilation occurs through openings greater than:
  • 1500 mm² per meter of length for vertical air gaps;
  • 1500 mm² per square meter of surface (wall) for horizontal air gaps.

The ratio between the aeration surface and the height of the wall must comply with certain numerical parameters to ensure proper ventilation.

For example, if one wants to achieve a weakly ventilated facade, the ratio must be less than 0.002 m²/m.

For a strongly ventilated facade, it must be greater than 0.05 m²/m.

For medium ventilation, it is sufficient to remain within a range between 0.002 m²/m and 0.05 m²/m.

To calculate the area of the ventilation opening, one must sum all the air entry openings, both the upper and the lower ones.

In general, as an example, under conditions of medium thermal insulation, temperature = approximately 20 °C, maximum relative humidity of the air of 60%, and a facade length not exceeding 15 m, a gap of 2 cm may already be sufficient. The gap usually has a width between 3 and 5 cm, without internal obstacles that could impede the airflow. Special ventilation grids are positioned at the base and the top of the facade to prevent the settlement of small animals and the accumulation of hard-to-remove materials.

It is advisable to avoid gaps greater than 10 cm, unless the ventilated facade has a length greater than 15 m. In these cases, the airflow may no longer behave laminar and may become turbulent, rendering ventilation ineffective.

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.

Operation and Material Layering of a Ventilated Facade

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

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“
• “Natural Ventilation: Everything You Need to Know for an Efficient Design”

Mechanical Ventilation

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.

Ventilated facade vs Rainscreen: what is the difference?

A ventilated facade and a rainscreen are systems used for better moisture management and energy efficiency. They differ because:

• the ventilated wall is characterized by the creation of a moving air chamber between the wall and the external cladding, improving the thermal and hygrometric performance of the building;
• the rainscreen, literally “rain screen,” represents a barrier that protects the building from rainwater, preventing it from penetrating and damaging the building structure, but without necessarily creating an air gap.

Choosing a ventilation system for the facade based on climate and building use

Ventilated facades have the ability to adapt to different climatic conditions and can play a significant role in improving the energy performance of buildings in various regions.

In cold climates, double-skin facades act as highly effective thermal insulators. The gap between the two skins creates an insulating air layer that reduces heat transfer from the inside of the building to the outside, minimizing the temperature difference between the inner and intermediate layers, thereby reducing heating needs.

In hot and dry climates, these facades act as natural sunshades, preventing direct sunlight from penetrating the building and reducing its cooling load. Additionally, the empty space between the two skins acts as an air channel, allowing for natural ventilation of the building and reducing the relative temperature of the intermediate layer.

In humid climates, these facades help improve thermal comfort conditions by controlling the relative humidity inside the building. The double-skin facade effectively reduces internal relative humidity by creating a barrier against moisture penetration from the outside to the inside of the building.

Ventilated facades and energy performance: choosing insulation

The inclusion of thermal insulation within a ventilated wall offers great opportunities in terms of energy performance.

When choosing the type of thermal insulation to use, it is important to consider characteristics such as sound insulation capacity, cost, conditions of the perimeter wall, and breathability.

The insulating materials used for ventilated facades are divided into:

• synthetic insulators, such as polystyrene and PUR;
• mineral insulators, such as rock wool and glass wool;
• organic insulators, such as cork and wood fiber.

Each of these materials will behave differently in relation to:

• thermal conductivity;
• thermal inertia;
• fire resistance;
• structural stability and durability;
• acoustic insulation;
• sustainability;
• cost;
• ease of processing.

Although none of the materials excels in all characteristics:

• synthetic insulators are low-cost and have high insulating capacity, but they do not have a long lifespan or high thermal inertia;
• mineral insulators have a medium-low cost and are made from recyclable and recycled natural raw materials. They have better sound insulation capacity than synthetic insulators, but lower thermal insulating capacity;
• organic insulators have excellent thermal inertia, breathability, and are sustainable. However, they tend to be very expensive.

The choice of thermal insulation is constrained by the need to ensure the creation of interventions that guarantee the energy improvement of a building.

Double ventilated facade: applications in tall and complex buildings

A double ventilated facade can be defined as a traditional single facade doubled inside or outside by a second facade, essentially glazed.

They are widely used in tall buildings because their use prevents energy losses in the building and helps reduce heating and cooling costs. Additionally, by controlling natural light and reducing the need for artificial lighting, they lead to energy savings. Consequently, buildings that use this type of facade have better energy performance.

Examples include 30 St Mary Axe and 1 Angel Square in London.

Operation of double wall facade

Cladding options for ventilated facades: from fiber cement to porcelain stoneware

Ventilated facades can be completed with customizable solutions based on needs: from glass surfaces, aluminum, natural stone, to finishes with photovoltaic panels on the facade.

Among the various cladding options, in recent years, fiber cement and porcelain stoneware facades have become increasingly popular.

Let’s analyze them in detail.

Ventilated facade in fiber cement: advantages for contemporary design

Fiber cement ventilated facades have gained significant momentum in recent years due to the need to combine aesthetic decor and energy savings.

Eco-friendly fiber cement defines the aesthetics of the building, helps protect it, and maximizes thermal and acoustic insulation.

The main characteristic of a fiber cement ventilated facade is the ability to create a flat surface, often devoid of any projecting architectural elements including sills and balconies.

This uniformity is sought after because it helps avoid temperature differences on its surface, thus eliminating the problem of thermal bridges.

Moreover, fiber cement can be customized in various ways: colors, appearance, assembly methods.

Ventilated facade in porcelain stoneware: aesthetic value and thermal performance

Porcelain stoneware is ideal for ventilated facades due to its numerous qualities, which perfectly meet the needs for resistance, aesthetics, and sustainability.

Ventilated facades in stoneware are very resistant to weather agents: rain, frost, or sun do not compromise the durability and aesthetics of the material.

Stoneware is very versatile, suitable for various types of buildings, from residential to commercial, from more traditional to more modern structures: large format slabs, wood effect, terracotta, and concrete are just some of the possible aesthetic characteristics.

Additionally, stoneware is sustainable and environmentally friendly, having a reduced environmental impact compared to other types of materials.

Benefits

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.

FAQ – Ventilated facade

What is a ventilated facade?

It is an external cladding system composed of multiple layers installed dry, including a continuous air gap that separates the cladding from the load-bearing wall. This configuration improves thermal, acoustic, and aesthetic performance and is suitable for both new constructions and renovation interventions.

What are the main layers of a ventilated wall?

The essential elements are: perimeter wall, insulating layer, air gap, and external cladding. All of this is connected through a metal structure and anchoring systems that support and space the cladding.

What is the purpose of the air gap?

The air gap allows for vertical air circulation, generating convective movements that improve thermal behavior both in summer and winter. It acts as a buffer zone against heat, humidity, and noise.

How can you distinguish between a weakly or strongly ventilated facade?

It depends on the size of the ventilation openings. Weakly ventilated facades have openings between 500 and 1500 mm²/m, while strongly ventilated ones exceed 1500 mm²/m. The ratio of ventilation surface to wall height helps define the level of ventilation.

How does the ventilated facade work in summer and winter?

In summer, the heating of the air in the air gap generates the chimney effect, which reduces the heat transmitted indoors. In winter, the air gap acts as an additional insulating layer, decreasing condensation and humidity.

What ventilation systems can be adopted?

There are two solutions: natural ventilation, based on the convective movements of air, and mechanical ventilation, which uses devices to ensure a controlled airflow.

How does the climate affect the choice of ventilated facade?

In cold climates, it acts as an effective thermal insulator; in hot climates, it reduces overheating by acting as a sunshade; in humid climates, it controls moisture penetration, improving indoor comfort.

What insulating materials can be used?

The choice can fall on synthetic, mineral, or organic insulators. Each has different characteristics in terms of conductivity, inertia, fire resistance, breathability, cost, and sustainability.

What is a double ventilated facade?

It is a double-skin system, often with a second glazed facade, used mainly in tall buildings to reduce heat loss, control natural light, and improve comfort.