Architecture is a continually evolving form of human expression influenced by cultural and contextual factors. While many of the problems we face today aren't directly linked to architecture, it has the ability to provide or facilitate solutions to these challenges. This has been evident throughout history, as societal issues have played a significant role in shaping our built environments. For instance, during the Victorian era, the infamous "Great Stink" led to the modernization of London's drainage system and urban layout. Similarly, the 2008 recession gave rise to the sharing economy and coworking spaces. Nowadays, the climate crisis is transforming the way we conceive architecture, seeking to reduce the carbon footprint of buildings and cities to achieve the Paris Agreement objectives. Given this backdrop, what challenges should we expect in the future?
In the upcoming years, some of the most significant obstacles we will face are related to establishing sustainable and enduring well-being in the built environment across all dimensions, including social and environmental aspects. To tackle these challenges, initiatives like the European Green Deal propose measures such as using more durable and reusable building materials, renovating existing structures, and improving energy efficiency.
The most sustainable building is the one that is already built. -Carl Elefante
As we face major architectural challenges, such as urban gentrification, the scarcity of adequate housing, the rapid obsolescence of buildings, and the imperative to improve their energy efficiency, some specific project typologies have emerged and gained prominence. These can be grouped into four categories: renovation, adaptive reuse, extension, and restoration of buildings. In this context, energetic retrofitting –the process of making improvements to an existing building or structure with the aim of reducing energy consumption– is now essential to upgrade existing buildings and enhance their energy efficiency by modifying their systems, including HVAC, lighting, insulation, facade elements, doors and windows. Among the numerous innovations present in the world of construction today, Sto and its range of materials and systems provide the foundation for energy-efficient improvements, while simultaneously enhancing the appearance and value of buildings. To showcase the value of energetic retrofitting, four typologies are presented and explained through projects that highlight the Sto products used.
Renovation
Architectural renovation is the process of updating an existing building or structure to improve its functionality, appearance, and value. This can involve small or large updates such as replacing the facade, roof, or windows. A common practice in architecture, it helps to extend the useful life of outdated or historic structures, revitalizing urban centers.
A prime example of this is the ShowPass project in Barcelona, where the interior and exterior of a 20th-century building were renovated to enhance the architectural value of the building through energy improvement while preserving the architectural and cultural heritage of the city. This renovation makes the building more resilient to future environmental challenges. During the renovation, a variety of low-impact materials were used to minimize environmental impact.
Specifically, the exterior of the building features facade coatings made with intelligent technology finishes that incorporate photocatalytic air-cleaning properties. Work was also done on the thermal envelope and the first floor and level of the building to improve energy efficiency. Overall, the ShowPass building strategies achieved a 77% reduction in greenhouse gas emissions. In addition, users enjoy near-zero energy consumption with high levels of comfort in the center of the city, protecting the facade against outdoor conditions, including the growth of fungi, and thermal control.
Another outstanding example of renovation can be found in Frankfurt’s Alt-Sachsenhausen, a neighborhood in urgent need of change, as its local businesses and attractions had fallen into disuse. Kleine Rittergasse 11 is a project involving an existing building that was commissioned to be renovated into housing and a studio, but saving the dilapidated building proved prohibitively expensive and structurally challenging.
As an alternative solution to renovating the area, the architects chose to recreate the gable roof and the basic shape of the houses in the area, simplifying it by removing some architectural elements. For the exterior design, 3D facade elements were used to create an afterimage effect, which mimics the phenomenon of seeing a blurred or distorted image after staring at it for a while and then closing your eyes. To achieve this effect, the panels were milled on a CNC machine. The architects chose to utilize perlite-based panels, carefully blending the joints to achieve a seamless appearance. This deliberate approach prevents the panel joints from detracting from the lines that convey the lingering presence of the old structure. Enhancing the facade overall impact is its monochromatic finish, which imbues the afterimage with a subtle quality.
Adaptive reuse
Adaptive reuse is the process of transforming existing buildings or structures that no longer serve their original purpose, by giving them a new use while retaining as much of their historic features and character as possible. Rather than demolishing them and building new structures from scratch, this approach seeks to adapt buildings to current needs and reuse them for new functions. The possibilities for adaptive reuse projects are varied, from converting warehouses into art galleries, to transforming government buildings into cultural centers, and many more.
This typology is often considered a sustainable alternative to new construction because it preserves existing resources and reduces waste and environmental impact. The Gabriela Mistral Cultural Center in Santiago de Chile is an example of how this approach can preserve a building and change its historical perception while improving its energy efficiency. This building, formerly used as a government headquarters, and now a space dedicated to arts and culture used two essential materials in its design: corten steel as the building's overall skin and an external wall insulation system.
The combination of these materials alternates in the facade design, with the corten steel creating a decorative composition of transparency and lightness in counterweight to the building's heavy historical and structural load, while the insulation system functions to keep the building thermally comfortable for its inhabitants, as it houses libraries, rehearsal rooms, a museum, and exhibition halls. In addition to improving the building's energy efficiency, this insulation system, like steel, provides high resistance to weathering and microorganisms, making it durable enough to accommodate its new use and extend the useful life of a building that was inaugurated in 1972.
In other cases, the adaptive reuse of buildings involves preserving most of the original structural materials with minimal intervention. The Urania Cinema Transformation project is an example of adaptive reuse where a former 1939 cinema has been transformed into a mixed-use complex of public spaces for various cultural activities, offices, and a café.
The building's entire concrete structure was well-preserved, showcasing the first concrete structures with structural ribs of its time. To minimize heat loss through the exterior wall, an External Wall Insulation System was used, which is non-combustible and resistant to mechanical stress, cracking, and impact, making it ideal for installation and resilience against climate adversities. For the facade, a neutral color was chosen from 1,400 shades in the StoColor System to harmoniously coexist with the original materials and remain within the color palette of the surrounding buildings. Inside, original brick walls, rough plaster, concrete floors, and ceilings were mostly preserved with minimal intervention.
Extension
This typology refers to the addition of a new space or volume to an existing building or structure, either vertically or horizontally. Typically, this is done to expand the functional capacity of a building, such as adding more rooms to a house or increasing the capacity of a commercial building. The design of an extension must carefully consider how it integrates into the existing structure, ensuring that it blends with the aesthetics of the building while addressing issues of structural stability, accessibility, and environmental sustainability.
When done correctly, an extension can enhance the livability, functionality, and value of a building, as well as its architectural character and appeal. An excellent example of this is the Residential & Commercial Building Renovation project, where the conversion and extension of the neoclassical building were integrated into the historic context of the city of Tübingen, Germany while preserving the stylistic autonomy between the original and new elements. External wall insulation systems were used for the new element as part of the thermal upgrading of the new building, in addition to being highly weather-resistant. This system helps to minimize heat loss through the exterior wall and provides excellent technical characteristics such as resistance to mechanical stress, cracking, and impact, in addition to adverse weather conditions.
The extension element is differentiated from the old building through a modern architectural language but forms an integral and natural part of the existing topography. To create the distinction between the two elements, a custom facade plaster was used that is cement-free, water and weather-resistant, and allowed for a distinctive surface texture with functional benefits.
There are also examples of more ambitious and larger-scale applications, such as the Royal Opera House building. In addition to renovating the facade, new public areas were incorporated into the ground floor interior, including a café, new stores, and informal spaces for events and exhibitions. Furthermore, the reception lobby and street-level entrance were renovated.
To address the acoustic challenges caused by pedestrian traffic and the presence of reflective materials in the building's extension, an Acoustic Suspended Ceiling/Wall Lining was installed in the new entrance lobby and reception spaces. This lining is a type of acoustic plaster for walls and ceilings, designed to seamlessly cover large areas.
Restoration
Restoration refers to the process of preserving existing buildings or structures of historical, cultural, or architectural significance. The main objective of restoration is to prolong the life of a building or structure by preventing its deterioration, damage, or destruction. It involves the careful examination and evaluation of the building's materials, structure, and historical context to determine the most appropriate and sustainable ways to repair or restore it.
As ancient cities have grown and changed throughout hundreds of years –as is the case of Abu Dhabi– some buildings of high historical value have become immersed in the urban fabric. This is the case of the Qasr Al Hosn Fort, the oldest and most important building in the city, built in 1760 as a watchtower to protect the only freshwater well on Abu Dhabi Island and later expanded to become a palace.
As part of the Al Hosn master plan, this building coexists with the goal of reinstating the fort as the cultural heart of the city, combined with a new type of urban landscape with local roots. To preserve the Qasr Al Hosn, a highly flexible and crack-resistant synthetic plaster finish was used, which imitates the original aesthetic of the building and blends in with the materiality of the master plan so that it maintains its integrity by resisting weathering while being vapor-permeable.
In this context, energetic retrofitting goes beyond just ancestral buildings. An outstanding example is the University of Graz Library, which involves the restoration of a 19th-century building along with an innovative extension. The restoration effort preserves the historical charm of the library, while a remarkable two-storey glass-fronted platform gracefully protrudes from the top of the historic reading room. One of the most notable features of this two-story platform is its potential to provide cover for the people on the staircase and the historic façade below, thanks to the cantilever. Additionally, the sgraffito on the soffit enhances the visual impact of this element, serving as a connection between the past and the future. This integration of old and new elements showcases the library’s commitment to energy efficiency and modern architectural design.
The outcome of this project is a harmonious blend of contrasts, as the existing listed building seamlessly integrates with the new construction to form a cohesive unit. Regardless of the building typology, this library serves as an example of how historic structures can preserve their original facades. Through the implementation of hydrophobic claddings, facades can be protected from the elements, while customized plasters replicate the textures of the original finish. Furthermore, in the case of extensions like this project, the incorporation of panelized ventilated facade systems enables efficient thermal insulation, effectively combining the best features of each architectural typology. Therefore, let's reconsider the Carl Elefante phase. “The most sustainable building is the one that is already built”. However, why not enhance it on specific occasions using combined strategies?
Energetic retrofitting plays a crucial role in improving energy efficiency and creating sustainable buildings across different typologies. By utilizing a diverse range of materials and systems, this approach prioritizes building with a conscience and practical solutions that enhance the overall performance of buildings, whilst improving comfort. With the aim of creating more energy-efficient and sustainable buildings, this approach seeks to achieve the dual purpose of reducing energy consumption and minimizing environmental impact.
For more information about Sto, visit their website or browse our product catalog.
