The global construction industry is going through a massive undertaking in both emerging markets and established one. According to the Global Construction 2025 report, the volume of construction output will grow by more than 70% and will reach an annual worth of $15 trillion worldwide by 2025. It is estimated that there will be 2 billion additional inhabitants, which will increase urbanization.

This has invariably increased the need for sustainable infrastructure and many governments in the Middle East are eager to promote ecological sustainability in the construction industry. Green building regulations have grown in impact over the last few years and fortunately, major construction companies operating in the GCC have already begun to demonstrate their commitments to both international and local sustainable building practices. This includes sustainable building façades.

The UAE has been especially making moves to switch to more sustainable and healthy buildings and among the practices adopted, the most widely used has been the use of facades. This feature in buildings is already a staple of the region’s traditions as it has served to protect against the desert heat.

Today’s building façades are more efficient because they include the installation of thermal insulation on windows and switching from fluorescent to LED lighting. This switch is an energy-conservation solution in green building concepts to reduce power consumption.

What are the different types of facades?

The building façade is the barrier between the interior and exterior environments. While the concern is to maintain a healthy and comfortable interior space and livable environment, the focus will be driven towards providing indoor thermal comfort. The solution is not only bound by air conditioning or heating systems when we have a sustainable option but also plays a vital role in reducing energy consumption and enhancing indoor thermal comfort.

Here we are going to focus on two main types of façade systems, one that serves as a second skin to protect the inner wall called the ‘double skin facade’ and the other that regulates the temperatures based on the materials used in the building, this is called ‘glass façade’. Both façade systems have resistance properties to improve the building occupant’s comfort and interaction with the exterior.

How does a building facade improve building performance?

Aesthetic Appeal

The façade is quite literally the face of the building. It creates an identity and is often what the public would use to describe a specific development; in short, the way it looks matters. Other than the overall shape of the envelope, which co-relates to the internal planning and layouts, the design of the façade should consider qualities such as modulations, texture, color, reflectivity, gloss level, as well as the possibility to incorporate patterns on the surface for daylighting or natural ventilation.

Structural System

Consideration of the structural aspects of the façade design is also vital. It needs to be able to withstand wind, live load, self-weight, seismic loads, as well as building movements under various conditions. All of the above must be accommodated for the full lifespan of the building envelope by understanding the size of the building envelope framing members, including the type of system, material strength, testing, design code, modulations, loading, and floor-to-floor height, amongst others.

Durability and Stability

The building envelope should be designed using materials and systems that are durable. As the outermost protection of the building, the façade of a building is susceptible to sun, rain, and other temperature variations. The maintenance of the façade is also something that needs to be taken into consideration when choosing materials as cladding materials may fade, crack, chip, chalk, debond, warp, or become scratched.

Weather Performance

One of the main functions of the building façade is to shield the occupants from the weather. This includes a proper thermal performance by limiting air infiltration and exfiltration, minimizing the risk of condensation and mold as well as preventing water penetration.

Acoustical Performance

Beyond limiting air infiltration, the building envelope should be designed to sufficiently limit external noise, in particular, traffic and mechanical equipment. The façade should also prevent self-generated noises, such as those that can occur due to the friction of metal on metal parts.

Thermal Performance

Each region has a different effect on building envelopes and therefore there is great importance on the contribution of heat load. In commercial buildings, heating and cooling systems can contribute up to 50% of the total energy bill so improving the thermal performance of the facade contributes to reducing the size of HVAC (Heating, Ventilation and Air Conditioning) systems, and lowering the energy cost of the building while in operation.

What is a sustainable facade?

When we say “sustainable façades” we expect exterior enclosures that utilize the least conceivable amount of energy to retain a comfortable indoor climate, enhancing efficiency to certain materials, which have a less negative impact on the environment. In other words, a green building façade. Sustainable façades can greatly reduce the building’s energy consumption and protect against weather and moisture.

A variety of additional measures can be taken to ensure sustainability such as including sourcing sustainable materials such as the use of recycled or recyclable materials, limiting or altogether avoiding the selection of components with high VOC (volatile organic compounds) content, ensuring that the materials chosen for the façade elements have been produced in ISO14001-certified factories, and incorporating building envelope components that can generate energy (from solar, wind or other renewable sources), etc.

Here are two examples of the types of façade systems.

Double-skin Façades

This design incorporates two façade layers; an insulated wall and a second shading or sheltering layer that shields the inner wall from the weather. There are various studies and emerging technologies on breathing facades. One such example is the use of metal mesh to create a second skin.

This structure uses a translucent metal mesh externally that allows air movement, provides shade and reduces direct sun exposure while allowing natural light to pass inside the building. Some factors need to be taken into consideration while selecting the color, distance between the mesh and the façade, and the light reflecting factor.

Figure 1 Metal mesh skin, The Hague, Netherlands (source: ArchDaily)

A ventilated façade (also known as Rainscreen Cladding) can be constructed with a double layer opaque wall with an air gap in between. The insulation layer will be installed at the inner wall and the façade cladding at the exterior wall. Air vents would be provided at the top and bottom of the wall allowing air circulation throughout the day. These vents can be opened and closed according to season and time of the day.

The air moving through the wall cavity creates a way of natural ventilation of the façade that as a result decreases the heat of sun rays and enhances the indoor thermal comfort. In addition to its energy efficiency benefits; this technique also protects the building materials and structural elements from weather and rain, as well as reduces humidity and moisture which evaporates quickly within the air gap.

Figure 2 Breathable facade illustration (Source: ArchDaily)

These types of enclosure systems allow the outer surface to ventilate naturally; reducing the reliance on fans and air compressors which come at the cost of noise and potential discomfort from sensible air movement.

Sustainable Glass Façades

Fenestration components like windows, curtain walls, and skylights are important elements of façade design. They allow natural light to enter the building and provide a connection between the outside and inside of the building. They also affect the building’s overall energy consumption. Fenestration materials and their properties drive the amount of energy utilization as well as the heat loss or gain of the building. Furthermore, the quality standards support the selection of window components and identifies the aspects that can reduce solar gains.

One such feature is Dynamic Glazing. It is defined as any fenestration product that has the fully reversible ability to change its performance properties, including U-factor, solar heat gain coefficient (SHGC), or visible transmittance (VT).” 2015 IECC

In recent years, architects and consultants have been coming up with an array of designs for digitally controlled sunscreens that move in response to shifting environmental conditions. One such technology is a smart system that controls the color or tint of the glass and works according to weather and time of the day. When the sky is cloudy and sun is hidden the glass will be clear, on the other hand, as the sun radiates during day time, the glass will be tinted to reduce the solar impacts (heat gain, direct sunlight, and glare) either automatically using intelligent controls and sensors or manually by BMS integration, touch panel or mobile device.

The dynamic glass tints electronically allows building occupants to choose the best level of natural light for their comfort. This has opened the path for more flexible innovations to be made. One such example is available where the glass panel can be divided into zones and the tint works variably on each zone (Light Zone) or the shade can transform gradually along with the glass panel (Glass Harmony).

Based on occupant feedback and the testimonial given by different clients on this technology, this glazing solution has:

• Improved the health and wellbeing perceptions by 54%,
• People are 40% more productive,
• Increased the visual comfort by 56%
• Improved daylight by 82%
• Enhanced workplace satisfaction by 73%

The recent wave of concern about sustainability and reducing buildings’ carbon footprints has spurred interest among architects in such systems. Design strategies for sustainable, high-performance façades highly depend on the building’s location and climate. We can see that the technologies and innovations emerging every day are intriguing and we will have more products that can aid the sustainability, environmental, and wellness objectives to provide a healthy and comfortable living atmosphere for occupants and reduce the negative impacts on the environment and reduce carbon emissions resulting from the excessive use of mechanical systems.

The building enclosure is a fundamental factor for building efficiency and adaptability. Combining efficient opaque construction elements with the right selection of glazing systems would have a great impact on Sustainability in all aspects including energy efficiency, occupant comfort and wellbeing, thermal comfort, visual comfort, and carbon reduction. As energy and other natural resources continue to be depleted, it has become clear that technologies and strategies that allow us to maintain our satisfaction with the interior environment while consuming fewer of these resources are major objectives for contemporary facade designs.

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