post detail page top

Enhancing Aesthetics and Performance: The Significance of Exterior Cladding in Buildings

By:

The importance of cladding in buildings goes beyond functionality and serves as a crucial aspect of modern architecture. It not only protects the structure, from weather conditions but also contributes to its visual appeal. The selection of cladding material, design, and installation technique greatly impact the building’s energy efficiency, durability, and overall aesthetic impact. With a range of options architects, designers, and builders can now choose from various cladding options to seamlessly integrate structures with their surroundings while meeting sustainability and durability requirements.

In this cover story, we will delve into the role of cladding as it has the potential to transform buildings into visually stunning and environmentally responsive works of art. For this, we have interviewed a few industry experts to bring to you all the important aspects related to cladding. Here are the excerpts:

Types of Exterior Cladding Materials and Criteria of Selection

According to Mathieu Meur, Director, DP Façade PTE LTD., there are hundreds of options in the palette of materials available to designers. These range from translucent or transparent materials, in particular glass and its countless declinations, to solid materials which include several metals (steel, aluminium, zinc, copper, etc.), various essences of timber, earth-based materials (ceramic, terracotta, bricks), cement-based options (architectural precast, GRC/UHPC, fibre cement boards), to a wide variety of stones, and much more too long to list down. Ultimately, it is up to the façade designers to leverage this enormous range of design options instead of confining themselves to the ubiquitous glass and aluminium which we sadly see on so many buildings, even though so many alternatives are available.

There is a wide range of cladding materials out there indeed that are too many to list within the context of this interview, and the criteria for choosing a material may vary significantly from building to building depending on its context and complex configurations of different factors.

Avinash Kumar, Executive Director, Godwin Austen Johnson, says in terms of cladding, we are mainly using concrete, metal, stone, and glass panels. The selection is entirely based on the overall design intent. While weatherproofing forms the key factor for selection, aesthetics equally plays a major role. Right from fixing type to the performance it achieves, there are various factors for selection. Performance criteria are very important in terms of human comfort and the overall well-being of the users. FLS is one of the very stringent criteria which needs to be reviewed while selecting and fixing any cladding material.

Materials can be listed in the following main categories.

• Wood: This material can be used as a structural and weathertight load-bearing exterior wall as well as an external facia (rainscreen) attached to a weathertight wall. It can also be used as a solar screen be it in the form of louvers or Mashrabiya-like lattice. Wood is normally considered a lightweight construction material, whereas certain types, like Bamboo, are heavy-duty and highly durable indeed, especially in hot humid environments, while having excellent thermal insulation qualities. The affordability of wood may vary depending on its source and application, especially when considering treatment against fire, pests, solar rays, and humidity. Depending on the wood type, its articulation, and treatment, it can vary in its application on façades to offer casual/cozy/friendly to high-end/luxury/elegant look and feel indeed, and therefore can be used on various building types from simple huts to luxury palaces. Wood cannot be recycled per se (like metal) due to its organic nature, but it can be re-used in similar or different applications, and where certain types (like Bamboo) can grow much faster than others (like Cedars).
• Stone: A heavy material that is normally used to project more permeance and monumentality (palaces, museums, memorials, etc.) as well as luxury and prestige (high-end residences and offices), as the material is considered heavy-duty (highly durable), fire-resistant, and relatively expensive compared to other streamline solid materials like render or precast concrete. Stone can be used for load-bearing walls (structural) and/or as an exterior cladding material (rainscreen). Stone cannot be recycled per se (like metal) due to its organic nature, but it can be re-used in similar or different applications. Stone cannot naturally be replaced within the lifecycle of any building as it takes a long time to form naturally, and therefore it should be used with a lot of careful planning to be re-used again, as our ancestors did that very well in the past.
• Clay-based: Like Bricks, Terracotta, Ceramics, etc. that undergo a relatively low-tech process (like baking) before they can be used for loadbearing and/or rain screen applications. Clay based products are relatively affordable while offering a variety of looks and feel (shiny/polished or matt/rough, of all textures and colours) for all kinds of applications (from heavy-duty tiles to decorative portraits). They are very durable and fire-resistant and are both recyclable and reusable in different applications.
• Render: This is one of the oldest and most established and affordable types of façade applications, which is mainly comprised of cementitious plaster and paint that are applied to a weathertight wall. Render can be articulated to form all kinds of patterns, textures, and colours, and can be applied to almost any geometrically complex surface. However, due to its manual application, render is always prone to poor workmanship, site conditions, and surface cracking, especially if other components are present behind it like insulation, or if applied at the interface between different building components like a slab and wall. Therefore, it is important to apply joints where higher building movements are expected. Furthermore, render is also available as more industrialised/standardised insulated products, otherwise known as Exterior Insulation Finishing Systems (EIFS) that can be applied to simple and geometrically complex surfaces while reducing (not eliminating) requirements for site workmanship. However, all EIFS components must be compatible otherwise the quality could be severely compromised.
• Precast Concrete: A very heavy and heavy-duty material and affordable indeed, that can take many shapes and sizes (units can reach up to 18m long), with fair-faced (raw look) or treated/ pigmented/painted finished surface. It is used on all types of building applications but generally tends to be avoided on high-rise buildings due to its heaviness which adds substantial dead-load to the main structure of the building. Precast Concrete is generally used for mid-end commercial applications like low-rise residential units and high-end fortified buildings like ministries and embassies. Precast Concrete cannot be recycled but can be reused in different applications.
• Glass: Due to advancements in glass technology over the past few decades, there are thousands of glass products out there that vary in colour and level of transparency and reflectivity. From lowiron (over 90% transparency) to mirrored glass (less than 10% transparency), glass can be used for all kinds of applications and building types. Like metal, however, while it can project slick high-tech/ sophisticated looks, too much of it can also create a sterile look and feel. Too much glass on a building façade can also compromise the comfort and privacy of occupants, in addition to compromising the energy performance of the building due to high heat gain/loss (whether applied in a hot or cold environment). Glass can come in single, double, or triple glazed units to improve thermal and acoustic performance. Glass can be flat, single or doubly-curved either by applying cold-bending (for relaxed curvatures – relatively cheap process) or warm-bending (for tighter curvatures – very expensive process as it requires special three-dimensional molds). Only certain types of non-coated glass applications can be recycled, otherwise, glass can mostly be re-used in different applications.
• Metal: Like Aluminium, Steel, Bronze, etc. metals are usually considered lightweight cladding materials (thin sheets) when compared to heavier applications like pre-cast concrete and even some composite materials like Glass Fibre Reinforced Cement (GFRC). Apart from commercial coated/painted applications like composite aluminium panels, metal cladding can offer unique and stylish looks like polished or brushed stainless steel, rusty bronze, or even rippled titanium. Metal can be moulded and shaped to create geometrically complex surfaces and can be relatively easily perforated due to its strong homogeneous nature. However, metal can also be relatively expensive to fabricate and supply, and difficult to maintain. While metal cladding can project slick high-tech/sophisticated looks, too much of it can also create an industrial/sterile look and feel, which may alienate people. While metal is one of the most recyclable building materials, it requires a lot of energy to do so. As they are generally considered lightweight cladding materials, both metal and glass are widely used on high-rise buildings.
• Composites: Like Glass Fibre Reinforced Cement (GFRC), Glass Fibre Reinforced Plastic (GFRP), and Carbon Fibre. While GFRC is the heaviest of the 3 applications, it is still considerably lighter than precast concrete while almost equally durable but significantly more expensive, and can be molded into various shapes and geometric surfaces, including complex doubly-curved or perforated ones. While less fire-resistant and durable than GFRC, GFRP can be manufactured into much larger pieces (units can reach up to 20 meters long), however, due to its high reliance on its fibres for its structural integrity, it likes relatively smooth and large surfaces and does not like perforations, like a boat hull or wind turbine blade. Both GFRC and GFRP are mostly used as non-load-bearing rain-screen cladding. Carbon Fibre is similar to GFRP albeit much stronger (3 times the strength of steel while 12 times lighter), however, both are prone to fire (can melt at relatively low temperatures) while Carbon Fibre is significantly more expensive than GFRP. Therefore, Carbon Fibre is only really recommended for niche and geometrically complex structural cladding features, like special canopies, signages, or exceptionally large cladding units. Being lightweight, relatively durable, and easy to mould and shape, composites are suitable for buildings that are geometrically complex and/or high-rise. Contrary to claims made by many suppliers, composites are not exactly recyclable but can be reused in different applications.
• Membranes & Meshes: Membranes are ultra-lightweight weathertight skins, like PVC or PTFEcoated Fibre Glass closed-weave mesh, or transparent/printed ETFE that come as flat or air-inflated units that look like large nylon cushions. Such materials can cover very large spans indeed, like stadia and shopping mall roofs, and are also increasingly being used as vertical façades. They are however prone to vandalism and sharp objects, and should therefore only be used in parts of the buildings that are out of reach of people. Open-weave meshes tend to allow water and air through, like PVC or PTFE-coated Fibre Glass open-weave mesh, or metal meshes that are mostly made of stainless steel or powder-coated aluminium, and mostly used as shading screens, decorative screens, or fences.

• 

  Vegetation: Plants can be used as an integral part of the external façade, which can serve as decoration, a shading screen, a privacy screen, like climbers, and help in creating a cozier micro-climate for occupants indeed. Depending on the type of vegetation used in a particular context, requirements for maintenance like applying pesticides, trimming, watering, etc. may vary significantly. Vegetation may also offer occupants customisation options when allowed to choose their plants to grow. Using vegetation as a façade element is growing in popularity, however, more education is needed to apply it correctly. For example, certain climbers may require a lot of watering and may also contribute to growing certain types of dangerous mold that can infect the inner parts of the façade causing serious health issues. Other types may attract a lot of undesirable insects and birds like mosquitos and craws respectively. Another way for using vegetation in building façades is by creating pockets or pop-out boxes within the building form to accommodate sky gardens or winter gardens, where plants can be grown and maintained in a more controlled environment.

Abdulmajid Karanouh, International Director – Head of Interdisciplinary Design & Research, Drees & Sommer

Impact of Environmental Factors on the Choice of Exterior Cladding Materials

Many factors come into play when selecting façade materials or systems. These include aesthetics, cost, performance, and more. When it comes to environmental considerations, it is essential to assess the durability of the materials through experience and testing. Beyond that, designers need to consider the thermal performance of the material and how this impacts the heat transfer between the inside and outside of the building. In many instances, it comes down more to the type of finish that is applied to the material than the base material itself, believes Mathieu.

Cladding is a “cover” to the building façade and hence this cover does protect the users inside and hence it must achieve the right thermal performance. It’s the right insulation and the thermal break properties that any cladding has to achieve to keep the external temperature away from the inner leaf of the building, says Avinash.

Environmental Factors that are Critical in Terms of Driving the Selection of Cladding Systems & Associated Materials

• Live-loads: The first factor that is normally taken into consideration is structural integrity and safety, which becomes especially critical the larger the cladding units and the higher the building becomes, due to higher live-loads (wind pressures and building movements) applied to the cladding. This factor becomes more complex once security requirements like blast-proof are added to the equation. The higher live loads are applied to the cladding units, the stronger yet more flexible the selected building material needs to be.
• Shading & Thermal Insulation: Another major driver is energy performance and the ability of the building to reduce energy exchange between the internal and external environments of the building. This includes the ability of the façade system/materials to shade the building during intense sunny conditions and to insulate the building during extremely hot/cold temperatures. The latter especially requires materials that are low in thermal conductivity like wood and rockwool. Plastic-based materials are also low in thermal conductivity; however, they should be used with a lot of caution as they are prone to burning or emitting high amounts of smoke if exposed directly to fire. Introducing air gaps or inert gases into façade walls is also common practice, like Insulated Glass Units (IGUs), double walls, hollow blocks, etc. However, if not designed and ventilated properly, façades with cavities can cause condensation and grow mold.
• Lighting: Another major factor is the ability of the façade to optimise and balance the admission of natural sunlight; too much sunlight causes overheating and glare, and too little creates a dim and lifeless environment of very low energy indeed.
• Weather tightness: This is the ability of the façade to keep rainwater out of the building while controlling (not preventing) air infiltration. This also includes incorporating a proper ventilation mechanism while minimising thermal bridging that could cause condensation, especially during highly humid conditions. It is important to emphasize that no façade system can prevent water and air infiltration 100%. Good façade design entails creating a system that can channel water, that manages to breach or collect behind the first line of defence, out of the building again, while controlling the ability of the façade to breathe. The latter is especially critical when it comes to condensation; some forms of condensation can be avoided by avoiding thermal bridging (contact of cold components with humid air), while other forms of condensation are inevitable during highly humid conditions and high due-point temperatures, therefore, the ventilation of cavities is very critical in this case to avoid the collection of condensed water causing water penetration, rust, mold, and other serious issues.
• Acoustics: The façade needs to be able to reduce noise, especially if surrounded by major sources of noise like highways and airports, or if subjected to highly windy conditions. Acoustics can be very tricky and counterintuitive in many ways. For example, if opening areas in a façade screen reach about 10% of the total area of the screen, it becomes almost useless as an acoustic barrier. Similar to thermal conductivity, using materials that are low in acoustic conductivity is a good starting point to reduce noise. Metal for example is one of the worst materials in terms of sound insulation due to its high-density and conductive nature, while double walls and IGUs with incorporated air cavities/chambers tend to be most effective in reducing noise. Also, varying the external and internal wall layers in terms of material and thickness (like combining hollow blocks with bricks with a cavity in between, or by introducing a laminated lite in the IGU) can increase the sound insulation quality of façades.
• Durability & Maintenance: Façade materials need to resist several environmental elements that could cause components to deteriorate quickly like solar rays, humidity, salination, dust and sand, and other air particles. That said, façade materials should be able to embrace (and not defy) such environmental elements to minimise requirements nt for cleaning and maintenance, and extend the overall service life of the façade. For example, cladding an entire tower with glass in a hot desert environment is counterintuitive on every level; technical performance, user comfort, and last but least cleaning and maintenance. The latter is especially the case as glass façades easily attract dust and sand that stick to their surface, which in return require a lot of water (a scarcity in desert regions) to clean. Furthermore, over-exposure to solar rays accelerates the deterioration of critical curtain wall components like gaskets and IGU sealants. Therefore, a careful study of the building context and maximising the use of indigenous materials that have withstood the test of time in the building environment is a good starting point in that respect. Finally, bird dropping is another major challenge that we face in maintaining building façades, and while many solutions have been applied over the years like spikes, poison, falcons, light reflectors, ultra-sound devices, etc. none has been entirely effective in keeping birds away from building façades. Therefore, attention to geometric articulation should be given to avoid creating unreachable corners where birds can safely nest.

Abdulmajid Karanouh, International Director – Head of Interdisciplinary Design & Research, Drees & Sommer

Importance of Thermal Insulation for Selecting Exterior Cladding Materials to Provide Effective Energy Efficiency

There are multiple aspects to consider when assessing the need for thermal insulation. In particular, one must consider the typical temperature profile throughout the year for the project being designed. This informs the designer on whether insulation is needed or not, and if so, how much insulation is required. This also determines on which face of the wall (internal or external) it is most judicious to place the insulation to minimise the risk of interstitial condensation within the walls or façade. There are other considerations, such as the fire performance of the insulation, and whether the insulated layer can be exposed to elements externally or not, says Mathieu.

Role of Exterior Cladding in Building’s Acoustics and Sound Insulation Properties

Mathieu believes that the building envelope has a substantial impact on the acoustic performance of the building, particularly in locations where high environmental noise is expected to occur, such as city centres or near airports. The façade designer must first understand what environmental noise contours will occur near the façade, then decide on acceptable noise levels within the building (this depends on the building typology), and finally carefully select the cladding materials and systems to meet these noise levels. It should be noted that any opening within the façade will cause severe deterioration of its acoustic properties, so these need to be avoided.

Finally, one must consider that different materials attenuate different sound frequencies more or less, so for more sensitive building typologies (such as performance venues), one needs to consider this in greater detail. According to Avinash, windows which are a must for any building must adhere to the right STC values to enable the acoustics performance. The absence of this would mean that the end-user will hear the external noise inside the space which can be annoying. Similarly, the overall external skin must be selected properly to keep the external ambient noise out of the building.

Ensuring Proper Water Penetration, Resistance, and Moisture Management

In many situations, the exterior cladding covers another sealed envelope located behind it, such as a concrete or brick wall. Water penetration is less of a concern in such situations. The most critical areas for water tightness are always openings (windows, curtain walls, etc.) and interfaces between different types of envelopes (for instance the junction between a curtain wall and a surrounding structure). The first and most important step is to properly design and engineer these façade systems. It is often also essential to fully test the systems, first in a laboratory to verify the design, and then again on-site to assess the workmanship. Extra attention must be paid to interfaces. Seals or flashings should be carefully detailed and verified at the site to ensure that the building envelope is fully watertight, opines Mathieu.

When it comes to external glazing, water infiltration details are very important to allow moisture and rainwater out of the building. We have observed that if the weatherproofing is not properly, it leads to water leakages inside the building during rains. So, it’s very important that the windows are properly weatherproofed to avoid water ingress, believes Avinash.

Concept of a Rain-Screen System and its Benefits in Exterior Cladding Design

Mathieu explains a rain-screen system consists of an exterior layer of cladding with open joints, and another layer behind it which is fully sealed to prevent air and water infiltration. This differs from the more traditional cladding designs, for which the external layer has sealed joints. The rain-screen approach is superior to this traditional sealed joint design, as the open joints allow the wind to pass through them, and to pressurise the cavity located between the cladding and back wall. Since the cavity is pressurised, rainwater does not get pushed (or sucked) through the joints by the wind. Therefore, although the joints are open, very little water, if any, is getting past the external cladding layer. Another advantage of this approach is that the absence of sealant in the joints greatly reduces maintenance requirements. Finally, since wind pressure is equalised between the two sides of the external cladding layer, the latter can be optimised structurally, resulting in savings in terms of the size or thickness of the cladding components.

A rain-screen is generally considered a lightweight external cladding layer that keeps most of the rainwater away from the weathertight line of the building. It does not contribute to the structural stability of the building as it is normally fixed to either a load-bearing wall or to a secondary structural system that translates the rain screen’s dead-load and live-load reactions back to the main frame of the building. A typical example of rainscreen cladding would be aluminium composite panels or EIFS render systems, says Abdulmajid.

Rain screen cladding is the cladding that covers the building from heat, window, and moisture, and the cavity can be ventilated or non-ventilated. The cavity has provisions where a limited water ingress can be controlled and it drains on its own. This cladding always helps in the aesthetics of a new building but it can be very effective in the case of renovating old buildings as well, believes Avinash.

Cladding Materials Performance in Terms of Fire Resistance

This is a very complex topic that could justify a whole book being written on it! Different geographies have different ways of dealing with the fire performance of façade. Broadly speaking, when selecting façade materials, the fire authorities of most countries require them to be non-combustible and not promote the spread of flame over their surface. Other aspects that are sometimes taken into consideration may include whether the materials produce flaming droplets or toxic smoke. However, this all only looks at the performance of the cladding material itself. The overall behaviour of the assembled cladding system should also be considered. In particular, the cladding system should not promote the spread of flame vertically or horizontally across the building (chimney effect), and it should also not allow the fire to spread from floor to floor. This requires the designer to carefully consider both the cladding materials and overall system construction, as well as perform testing on both the materials and systems to verify their respective behaviour, suggests Mathieu.

According to Abdulmajid, a good starting point is to understand and appreciate that there is only so much that can be done to prevent fires from breaking out and reaching the building façade, simply because most interior finishes comprise combustible materials like fabric, wood, and plastics, that always tend to catch fire and reach the façade easily. It is also important to highlight that most fire-related fatalities are due to suffocation from toxic smoke, less so much from burns. Therefore, in addition to avoiding using combustible materials on façades, it is equally if not more important to make sure that façades are designed in a manner to compartmentalise each floor to minimise smoke spreading from one level to another. Last but not least, most internationally recognised fire tests are designed to keep the fire from spreading from one level to another long enough (around 45 minutes) for firefighters to reach the building site. However, during special events like New Year’s Eve, traffic congestion may delay the arrival of firefighters which may have catastrophic consequences as fire can quickly spread out of control. Therefore, avoiding using materials that can become fuel to fire or generate a lot of smoke is always the safest bet.

With the above said, brittle materials like stone, cementitious or clay-based applications tend to perform best in terms of fire resistance as they do not ‘burn’, melt/drip, or generate smoke when directly exposed to fire, and are therefore considered among the best choices in that respect. Both glass and metal cladding do not burn or generate smoke as such (if free of plastic components) but may break/melt if exposed directly to the fire. While fire-resistant glass products exist out there, comprising multi-laminated layers, they are mostly used for internal applications as opposed to exterior cladding. Wood, PVC, and other plastic based combustible materials need to be used with caution; they may be used as external shading devices but should be kept away from the main skin of the building, especially on high-rise buildings. PTFE-coated fabric and ETFE membranes simply evaporate and emit little to no smoke when exposed directly to the fire. Overall, the façade consultant needs to distinguish between different types of façade components and choose the right material accordingly; main structural components need to be more fire resistant than others, weather-tight skins need to avoid emitting smoke, and decorative materials need to avoid burning/dripping.

Avinash believes that it is the flame spread that defines the overall flame propagation. In normal cladding, the flame spread is controlled and also there are cavity barriers that contain the fire in specified zones or floors in the unfortunate case of a building fire. The whole idea is that the flame spread should be as per code and secondly the flame/fire should be always controlled in zones in case of fire so that the whole building is not affected.

Common Challenges Related to Exterior Cladding Maintenance and Strategies to Ensure Longevity and Durability

According to Mathieu, the most common challenge is that many building owners expect their façades to be maintenance-free in the literal sense! No façade is ever maintenance-free, but designers can certainly minimise maintenance issues through simple design considerations, such as selecting materials adequate for a specific geography and weather conditions, minimise the use of customised elements (to facilitate future replacement), managing the flow of rainwater within the design (slope horizontal surfaces away from the façade, including drip grooves/edges, etc.) and minimise or avoid the use of materials that could increase the level of maintenance required (e.g., certain types of sealant). Any building needs access to the façade for general maintenance. It can be cleaning or replacing the panels or system installed. For general BMU systems, we do have limited options which many times does clash with the building design, and architects try to avoid the same. We need more robotics, suggests Avinash.

Recent Advancements in Exterior Cladding Technologies to Improve Performance or Sustainability

Sustainability has been at the core of our designs for a very long time now, so it has become second nature. There are always means of improving, though, so very intense R&D efforts are being expanded to make our façades even more sustainable. Some of the interesting technologies that I have come across recently include an LCD panel and laminated glass hybrid which has the potential to revolutionise façades by allowing designers to modulate the passage of light and heat through the glass to extreme levels, and largely independently of each other. Another interesting development to watch out for is that of clear photovoltaic glass, allowing building façades to generate electricity not only from the spandrel zones but also from the much larger vision areas. Several other research and manufacturing efforts are geared towards reducing the carbon footprint of the building envelope, not only from the point of view of embodied carbon but more importantly from cradle to cradle, says Mathieu.

Abdulmajid says maximising passive features and the use of indigenous materials that optimise natural ventilation and admission of diffused natural light while minimising the need for cleaning and maintenance respectively is always a good start to sustainable façade design. That said, automated mechanised solutions (external shading devices, operable vents, electrochromic glass, etc.) linked to sensors and a central computerised control system may also assist in improving and optimising the building façade performance, especially in office buildings. Renewable technologies like photovoltaics and wind turbines have only proven to be effective/efficient on low-rise buildings that do not require high amounts of energy to run, but have been less successful on high-rise buildings. There’s also been a lot of experimentation on self-maintaining materials, but none have been considered established enough yet for mass/ commercial use.

Exterior Cladding Affecting the Overall Sustainability of a Building

Sustainability efforts follow several different axes. Some of the design strategies involve selecting sustainable material (responsibly sourced, based on a high level of recycled content, featuring lower embodied and operational carbon, etc.). Other efforts consist in developing façades that offer the best possible thermal efficiency, thus reducing one of the largest sources of heating or cooling for a building (and thus reducing its energy demand). Yet another approach involves generating electricity from the building envelope, which in turn reduces the demand for fossil energy sources. Interestingly, making the building envelope more sustainable often does not involve a substantial, if any at all, premium on its lifetime cost. It is often a case of being creative and exploring other avenues of achieving the desired outcome, notes Mathieu.

According to Abdulmajid, maximising passive design features and using indigenous materials to minimise the need for energy, water, and overall maintenance requirements is a good starting point. Indigenous materials can cope with the building’s surrounding environmental factors a lot better than imported or chemically/industrially processed ones. Furthermore, indigenous materials can be recycled or reused more effectively in the same context as well.

The cladding does help in reducing energy bills and hence aids in the sustainability aspect. Now the cladding material proposed must be also sustainable and that’s a challenge. So, it’s ‘stringent that the materials being proposed are either reusable or can be recycled once the end of life is achieved. At times we opt for highly recycled contents or local materials where the carbon footprint is regulated and lesser than our counterparts, says Avinash.

Building Codes or Regulations that Pertain to Exterior Cladding

These fall under two main headings: regulations, which are dictated by local authorities of a country or municipality and which must be obeyed, and standards, which may or may not be followed, depending on the specifications for particular projects. Regulations may cover several design aspects, the most common being structural and safety considerations, fire safety, and environmental performance. Standards may define certain minimum performance requirements (thermal, water-tightness, air-tightness, acoustic, etc.), or they may describe testing procedures for the cladding materials or system. Interestingly, given the wide palette of materials that I mentioned earlier, we often come across situations where there are no standards available to guide us on the selection or use of a particular material or product. In such situations, it comes down to the experience and knowledge of the designer to be able to make judicious decisions and recommend bespoke tests if needed, explains Mathieu.

There are many internationally recognised building standards that cover building façades like ASTM (American) BS (British), and ES (European) among others, in addition to local ones that every country has in place. However, such standards are designed to offer guidance for minimal requirements, and not for optimal/best design practice. Therefore, utilising international standards is important from a contractual standpoint, but is not often sufficient to achieve optimal design solutions and apply best practices. Therefore, design teams should be able to formulate their project-specific design criteria and standards while aligning with internationally and locally recognised ones, says Abdulmajid.

Avinash notes that in several countries, the U values and Solar heat gains are regulated by stringent codes which helps to reduce the overall solar gains. Apart from this, the glazing area is also monitored and regulated in codes which do help in controlling it. In some cases, if the glazing area is more because of design, the Architect needs to demonstrate other means of control that reduce the overall energy usage. So, generally, the design is not affected by the building regulations and codes and all we need is to design incorporating the codes.

Investment in High-Quality Exterior Cladding Materials for Potential Long-Term Savings

On average, the Capital Expenditure (cost to build) vs the Operational Expenditure (cost to run/operate) is around 20% (CapEx) vs 80% (OpEx) of the overall whole lifecycle cost of the building. Therefore, investing more capital to build a better-performing façade to improve the overall performance of the building and minimising the required resources and costs to run it is a no-brainer in every measurable way. However, the main problem that we face is that developers/investors who build proprieties to either let or sell to end-users/occupants who ultimately pay for their own utilities and facility management bills, are less interested in increasing their capital investment in return for lower operational costs or a more sustainable outcome. Furthermore, developers/investors along with their consultants will always find ways to make their designs look better on paper than in reality for obvious commercial/marketing gains – consequently why enforcing regulations has failed considerably in that respect. Therefore, new business models and regulations should be devised to incentivise (as opposed to force) developers and investors to invest in producing better quality building façades, as opposed to taking shortcuts for short-term gains, opines Abdulmajid.

Avinash says the one-time capital cost ensures that the operational costs are smaller and in a matter of few years, the break-even is achieved where you compensate the extra capital spent at the inception. We have very good examples where the high U values of the façades have helped to reduce the solar heat gain and finally, it affected the AC loads and eventually, the energy bills were down.

Conclusion

In the world of architecture, cladding goes beyond its purpose and becomes a fundamental part of both aesthetic and sustainable design. It not only protects buildings, from the elements. Also serves as a canvas for architects to blend their structures with the surrounding environment. Architects use materials and techniques to ensure durability and energy efficiency in their creations. Cladding is more than a shield; it transforms buildings into environmentally conscious masterpieces. This intricate interplay, between vision, sustainability, and innovation turns cladding into a force that shapes edifices into responsive and long-lasting works of architectural finesse.