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The Realm of Cladding is Experiencing a Surge in Product Advancements
Could you provide an overview of the different types of exterior cladding materials available, and what factors should be considered when selecting them?
Choosing the appropriate cladding material is not just a matter of the architect’s design considerations, such as the client’s preferences, budget, structural loads, context, performance against environmental conditions, and the design’s geometry and materials properties that match it. It is also essential to ensure that the chosen materials comply with sustainability and embodied carbon certifications and goals, including energy efficiency, long lifespan, and recyclability. From cladding sheets to composite panels, shingles, and sandwich panels, the available cladding materials offer a comprehensive selection of all types to meet all your needs.
Some commonly used cladding materials include metal (such as aluminium, ACP, zinc, copper, brass, galvanized steel, and MCP), glass, stone (including granite, marble, limestone, travertine, and sandstone), plastics (such as FRP, polycarbonate, ETFE cushions, and UPVC), wood/timber (both natural and WPC), concrete (including GRC, UHPC, and fiber cement board/Hardie board), fabrics (such as PVC coated polyester), brick/clay (ceramic/ Porcelain, adobe brick, bricks, veneer, and terracotta panels), EIFS (as a system), stucco, and GRG (rarely used). Considering the current global situation, it may be necessary to use locally available materials. However, architects may need more support regarding the available finishes, sizes, and colours offered by local suppliers, which could affect their designs and potentially increase costs.
There is a trend in the Middle East to use adobe bricks to enhance the cultural significance of mudbrick in a modern style for newly constructed buildings while also restoring and retrofitting older ones. Using conventional cladding material has a drawback, as it presents limited flexibility against imposed deformations, such as those caused by changes in temperature, building movement, and elevated weights that require costly connections and mounting operations.
How do environmental factors, such as climate and exposure to sunlight, impact the choice of exterior cladding materials?
In the scorching hot regions of the Middle East, the cladding material used for the building’s exterior must withstand harsh environmental conditions. This is crucial to ensure it remains intact and unaltered even during sand storms in certain months of the year. We take great care to address the mitigation of water and air leakage, handling wind loads, preventing heat and thermal conductivity, avoiding acoustical intrusion, and controlling solar considerations to achieve the desired level of indoor comfort. Regarding cladding materials, it’s essential to consider each type’s specific properties and characteristics. For instance, concrete cladding is porous and has high thermal conductivity and soundproofing qualities, so it requires a combination of WRB and insulation to prevent moisture transportation and improve energy efficiency.
Stone cladding, on the other hand, is durable and environmentally friendly but prone to water retention and staining, which can be mitigated through a rain-screen system. Brick cladding requires sealing to prevent moisture damage but offers good thermal resistance and sound insulation. Steel and metal cladding also require insulation to counteract their high thermal conductivity, while glass cladding needs to be less transparent and more reflective to reduce solar heat gain.
Finally, wood cladding is porous and prone to decay from insects and fungi, so it’s recommended to use engineered wood that has been treated and coated for more e xcellent resistance to moisture and swelling. Manufacturers offer solutions to help architects use materials in different climates, such as composites and coatings. These treatments protect against mold, corrosion, and colour fading or damage.
In terms of thermal resistance, what are the considerations for selecting exterior cladding materials that provide effective energy efficiency?
You can now run mind-blowing 3D building energy performance analysis using cutting-edge tools like Design-Builder! When choosing energy-efficient cladding materials for your project, conducting a Life Cycle Assessment (LCA) and carbon metric is important for final sustainable solutions. When choosing cladding materials, the cost can often be a significant factor. However, it’s worth remembering that by investing in energy-efficient options; clients can save on operational costs in the long run. With careful consideration, the benefits can outweigh the initial expenses.
With a click, you can get energy usage, heat gain-loss, ventilation, CFD output, and HVAC loads through detailing graphs. And the best part? You can even visualise it all on Sketch-up! But that’s not all. With other thermal design simulations like WUFI and THERM, you can weigh the pros and cons of different materials and make informed recommendations. Get ready to take your project to the next level with these exciting tools! The selection process is focused on cladding materials that can effectively reduce embodied carbon, which refers to the total energy required for the extraction, processing, transportation, installation, reuse, and recycling of material.
Recladding or over-cladding must be cautiously approached regarding retrofitting buildings to meet net zero carbon global standards. Adding insulation behind the existing cladding can increase costs by up to 20%, but it is worth it. Various types of cladding offer energy efficiency, including stone, brick wall, stainless steel, and aluminium. You must be wondering if there are other alternatives to consider. The thermal conductivity of wood is influenced by various factors such as the type of wood used, direction of measurement (parallel or perpendicular to the fibers), density, and moisture content. Wood and wood products have lower thermal conductivity values than other materials.
EIFS is a popular choice for an energy-efficient and cost-effective lightweight cladding material that can mimic the look of building materials such as brick, stone, metal panels, siding, and stucco. It can also be used as a retrofit over existing claddings. However, improper installation of details at penetrations can cause water infiltration problems, the system’s thermal bridging, and excess ventilation. Fire resistance is also a challenge. IMP (insulated metal panel/sandwich panel) is chosen for its lightweight design, easy dismantling and reinstallation on a different building, and recyclable metal content. However, this system’s cost of materials is generally higher than standard wall systems.
Rammed earth/Adobe earthen cladding materials are chosen for their exceptional thermal mass, providing energy efficiency while being a renewable source of material. Terracotta panels can be sprayed or ram-pressed into various mold shapes. By partially glazing these panels while maintaining a lightweight sub-structure, you can contribute to carbon reduction compared to fully glazed or heavier flat terra-clad. Combining clay, glazing, and recyclable pigment sourced from industrial waste makes it possible to achieve a greater level of carbon reduction. Good craftsmanship and consistent insulation thickness can help lower cooling loads and achieve appropriate thermal transmittance and solar heat gain coefficient.
How does the selection of exterior cladding impact a building’s acoustics and sound insulation properties?
For the exterior façade, an STC of at least 45 is necessary to block out street noise effectively. It’s fascinating to learn about! I came across how certain properties of cladding materials can impact their ability to block out sound waves. Specifically, reflectivity, porosity, and density can all affect a material’s STC (Sound Transmission Class). To save time for façade consultants and architects, acoustic consultants should conduct proper testing and simulations to provide an analysis for each cladding material sheet. For high-quality acoustic cladding, it is essential to consider the acoustic barrier/damper, system depth of the exterior wall assembly, insulation, and connection seal. Timber, porcelain, and GRC are recommended cladding materials for an efficient overall system.
Acoustic problems often arise in private spaces susceptible to noise from HVAC rooms, cooling towers, and outdoor street noise. However, minor acoustic concerns can occur from one room/space to another. To address these concerns, it is recommended to use practical sound barriers such as closed cell foam (CCF), acoustic gypsum board, and dense mineral wool. These materials can help achieve an STC rating of 45 for public spaces and 45-50 STC for private rooms. In addition, cladding panels with a cavity, such as a rain screen, can provide good sound insulation.
Outdoor-Indoor Transmission Class (OITC) is a single-number descriptor used to identify the noise transmission properties of a building envelope or façade. OITC varies from STC in that the applicable third-octave bands extend to lower frequencies to account for the typical range of exterior noise sources. Higher OITC ratings correspond to more significant noise reduction. Furthermore, profiles with specific shapes can also help reduce the impact of sound waves. Even the louvers can have different depths and shapes based on their acoustic sound properties, but they are all costly, causing the overall cost of the façade budget to increase. Using SoundPLAN software to analyse the exterior enclosure during initial design thoroughly ensures a comfortable sound level and budget-friendly façade.
What are the key factors to consider when designing exterior cladding systems to ensure proper water penetration resistance and moisture management?
To achieve the best water resistance and moisture management, it’s important to understand the different forms of water in a cladding assembly. You can ensure a reliable and effective solution by thoroughly understanding the three levels of defense/control in cladding system design. It’s also crucial to manage the driving forces that cause water to penetrate and migrate through the cladding assembly materials. These forces include kinetic energy, capillary action (for Stone-concrete), gravity (for surface tension), wind pressure (which can push water inside cladding joints), and pressure non-equalization (which can push, pull, dry, and prevent moisture in the assemblies).
The three essential control layers are: First, a face-sealed non-porous cladding material must be used to withstand harsh weather conditions. Properly seal all joints between panels with suitable sealant/gaskets. Second, apply a liquid weather-resistive barrier (WRB) to the wall to prevent water vapour or condensation from penetrating the wall. This step is crucial, so pay close attention to it. Finally, incorporate a drainage path/ cavity with EPDM and flashing to eliminate residual water or vapour and prevent mold or fungus growth due to absorbed moisture. By following these control measures, you can ensure a sturdy and moisture-free building structure.
Use simulation software like WUFI to analyze air moisture performance. It can model complex assemblies to predict moisture penetration. Moisture penetration can cause structural integrity/safety issues and raise heat resistance by deteriorating insulation panels when accumulated in the assembly. Terracotta cladding is more effective than regular masonry when exposed to water since it has been heated and can have partial glazing adapted to function. During construction, field tests should be made for assembly. Also, It is necessary to dry any construction materials that become wet during assembly to prevent them from getting trapped inside the enclosure, causing damage.
What is the concept of a rain-screen system and its benefits in exterior cladding design?
In today’s market, there exist three distinct types of rain screen cladding: vented (enabling upward dryness), drained and vented (allowing for upward dryness and downward drainage), and pressure equalised (neutralised). A rain screen comprises several components, including facing panes, mounting brackets that create a cavity for air circulation, drainage, and moisture evaporation, a thermal insulation layer attached to the cladding, and a weather-resistant barrier mounted directly to the building structure. The barrier prevents vapour diffusion and air from coming into contact or being absorbed by the wall.
Rain screen cladding offers numerous benefits, including weather resistance, reduced thermal movement, and soundproofing. It is also highly durable and requires minimal maintenance, preventing warping, rotting, and decay. Additionally, it can function as a chimney to improve heating and cooling efficiency, ultimately reducing energy costs. By incorporating rainscreen cladding, you can make buildings more breathable and recyclable achieving sustainability certification goals.
How do different exterior cladding materials perform in terms of fire resistance, and what are some fire safety measures to be implemented in cladding design?
Cladding materials are assigned a fire rating on a scale of A to D, with the A being more fire resistant and the D being less fire resistant. Manufacturers determine the rating through prior material testing, which complies with NFPA 285, ASTM E119, building regulations, and IBC standards.
Cladding materials rates are affected by factors including their ignitability/combustibility, which determine the likelihood of catching fire based on temperature. Additionally, flammability plays a role in the rate of fire and flame spread. Resistance is essential to determine whether the material can withstand fire without structural integrity damage. The reaction that rates the heat and smoke release is another factor to consider, as well as the factor that signifies the potential for fire propagation to other areas. It’s crucial to consider all of these factors to ensure the safety of buildings and those inside them.
For tall buildings exceeding 18 meters, it is a regulatory requirement to use certified FR (fire-rated) materials for cladding. Testing the material and the entire cladding assembly for combustibility is crucial. Safety should always be the top priority when constructing any building. For cladding with high ignition temperature, opt for Aluminum, steel, stone, and terracotta/brick with a class A rating. It’s best to steer clear of UPVC, MCM with class C or D, composite metals/MCM (non-retardant core), and ETFE assembled vertically, as they can encourage flame spread. If MCM is necessary, go for one with a fire retardant core to ensure maximum safety.
When designing a façade, it’s essential to consider the cladding panels and implement safety measures to reduce fire risk. One way to do this is by using a high-density mineral fiber core as a thermal insulation barrier and fire stop. Additionally, using special coatings on the cladding facing can further increase safety. Combustibility is highest in the WRB within the cladding assembly, while mineral insulation is the lowest noncombustible element. To minimise risk, it’s recommended to reduce the thickness of the EIFS cladding system and use mineral insulation instead of foam insulation.
What are the common challenges or issues related to exterior cladding maintenance, and what strategies can be employed to ensure longevity and durability?
Maintaining cladding in office buildings, observation decks, and public spaces can be a challenge when there are high levels of user occupancy. Adverse weather conditions such as speedy wind and rain may result in postponements or even cancellations of the maintenance operation for the day. When it comes to maintaining weather resistance and aesthetics of a building façade over the long term, regular maintenance (including cleaning, replacement, and repair) is essential. In the past, cladding maintenance could be quite challenging due to the need to dismantle overlapped panels over the façade. However, today’s system designers have implemented much more easily-dismantlable methods of fixation, which make installation and panel replacement a breeze. With these advancements, maintenance is now easier than ever before!
The client’s budget determines the frequency of cleaning and maintenance cycles, which includes the time required to clean the entire building’s cladding, the number of crew members needed, and the number of cleaning cycles per year. Using non-pressurised water is crucial to prevent any damage to the joint seal. A compromised seal can quickly become permeable to heat, water, and air, leading to costly repairs. Furthermore, it is highly advised to use only soft and gentle cleaning materials that won’t cause any chemical reaction or fade the paint colour of the façade facing. Maintenance sometimes involves dealing with mold and fungus and checking for corrosion in flashing. To ensure the longevity and durability of a façade system, selecting suitable materials, conducting performance tests, and performing regular maintenance after installation are essential.
Could you discuss any recent advancements in exterior cladding technologies that have improved performance or sustainability?
The realm of cladding is experiencing a surge in product advancements. Modern cladding panels now blend various materials and alloys into one product. This has reduced object mass and material usage while maintaining structural integrity. These achievements have been made possible by utilising lattice-based design and topology optimisation techniques, enabling high-strength capabilities. Cladding is now available in natural stone or wood tones, patterns, finishes, and colours that are composed of plastic, concrete, aluminium, and porcelain.”
The manufacturing industry increasingly recognises the importance of energy conservation and cradle-to-cradle products (cradle-to-gate). Cladding materials sent directly from the design model to manufacturing machines are becoming popular to meet the demands of fast-paced, complex geometrical projects. This approach saves time and costs and helps ensure a seamless and efficient manufacturing process, especially if the assembly of panels can also be made through robotics. Regarding sustainable cladding design technology, the economic and energy efficiency performance of façade cladding is crucial in decision-making. In the design phase, technologies are shifting towards algorithmic-parametric models using customized programmed scripts instead of conventional CAD.
The integration of AI in design, automation, manufacturing, and open software programs, as well as the integration of software like Grasshopper in Revit, is already happening. To generate a panel design for your project, you can use two options: Use the mid-journey software or employ Python scripts with Grasshopper. As a result, the design process is now becoming fully sustainable.
Due to high energy demands, conventional manufacturing processes are becoming outdated compared to sustainable manufacturing technologies. This significantly affects the overall environmental impact of a product and its energy usage. Manufacturing building materials alone accounts for over 80% of the energy used in building construction. Therefore, the focus should be on improving and optimizing re-manufacturing processes, considering processing time, costs, manufacturing quality, resource consumption, environmental impact, and waste reduction.
Current innovative technologies focus on improving the planning, design, operations, and maintenance of production systems while improving products for clean production (CP). To minimise processing time and carbon emissions, optimum cutting speed and feed rate must be optimised. Multi-objective parameter optimisation is proposed to consider a balance of process efficiency. Some examples of such technologies are CRM (Customised Repetitive Manufacturing of Models) and AM (Additive Manufacturing).
CRM replaces conventional CAM (Computer-Aided Manufacturing) for complex buildings with repetitive similar panels. It revolutionises cladding material manufacturing from design to production. CRM production runs mostly with 10,000 custom-made repetitive units of cladding. On the other hand, AM is more significant with potential for long-term production than traditional subtractive manufacturing (SM) and may result in considerable material and energy resource savings. It can reuse cladding material and create a healthy environment free of pollutants. AM is a breakthrough production of parts with complex geometry. However, AM is still in its early stages and requires further research to lower material and machine costs, create quicker and more accurate printing processes, and function autonomously.
Microwave Processing (MWP) of materials and heating technology is another novel manufacturing route that can be used for processing ceramics, metal matrix composites (MMC), fiber-reinforced plastics (FRP), alloys, metals, material joining, coating, cladding, materials synthesis, etc. In previous years, the market share for 3D printing of plastic/concrete panels and molding technologies such as wood-molded blown glass was anticipated to grow. This is particularly true for repetitive panelling, where a single mold prototype can be used for multiple panels.
Virtual models and digital twins are essential as sustainable operational and maintenance technology in smart manufacturing, as they enhance the design phase through to operations. BIM 3D models provide a clear visualisation of the construction and design of an asset, while digital twins allow for virtual interaction with the asset. With digital twins, buildings can stay current with future trends and needs rather than becoming outdated. These advancements have significantly improved cladding performance and helped achieve sustainable enclosure goals.
How does exterior cladding affect the overall sustainability of a building, and what sustainable materials or practices are commonly employed in cladding design?
Did you know the construction material industry contributes to 11% use of CO2 emissions, 40% of total energy consumption, and 45% of generated waste in the EU? And that’s not all – 40% of summer overheating is caused by façades/envelopes, while 50% of energy bills go towards heating and cooling (HVAC).
Timber usage in cladding, CW, and CLT structures. Timber is at least as suitable as aluminium and steel to meet architectural and structural requirements. It has excellent thermal insulation and low carbon emissions, and wood is one of the preferred materials for current and future sustainability demands. Sustainable enclosures enhance circular economy practices with their eco-friendly materials. They should have energy-generating capabilities, a low heat transfer coefficient, and the ability to harvest fog and rain.
Additionally, they should have minimal embodied carbon and no volatile organic compounds. Furthermore, they should have low impact, reduced material quantities, and be reusable. Lastly, they should be integrated and produced with recyclable materials. Several sustainable cladding materials are available, including stone, thermal-modified timber, rammed earth, recycled plastic, recycled textile waste fabric, reinforced cement board, and recycled brick. Bio-based composites are another option that can enhance a material’s efficiency through renewable, recyclable, biodegradable, low specific gravity, and high distinct strength advantages.
Timber is just as suitable as aluminium and steel. However, the use of timber in cladding, CW, and CLT structures is a viable option that meets both architectural and structural requirements. With its excellent thermal insulation and low carbon emissions, it is becoming one of the preferred materials for sustainability demands, both present and future. By blending wood panels with stone, a long-lasting and fire-resistant material can be produced that retains the appearance of real wood. However, bio-composite materials have drawbacks, such as poor moisture resistance (hydrophilicity), fiber/matrix incompatibility, supply logistics, low thermal stability, flammability, poor electrical properties, extraction, processing, and surface modification.
Bio-composites include hemp, wood, date palm wood, cork, alfa, and straw. Like hemp concrete, using locally harvested straw in cladding panels can add to your sustainable goals. Additionally, 3D-printed bioplastic cladding panels can be fully recycled after a building’s end of life. These products are created using prior life cycle assessments and are manufactured in certified factories. To ensure optimal performance, an energy-efficient façade system should be incorporated during the early stages of design, and proper analysis should be conducted using Product lifecycle management (PLM). The designer and manufacturer are responsible for staying updated and committed to evolving sustainability standards, emerging technologies, and industry trends through ongoing learning and adaptation.
Some cladding materials that are considered sustainable may need to be more environmentally friendly during their manufacturing process. For example, stone is a sustainable material in operation, but the extraction and processing of its raw materials can have a high environmental impact. Timber tree-cutting methodology is considered to have a negative effect despite its sustainability. By implementing a rain screen system, cladding materials that permeate water and heat can be more energy-efficient and sustainable.
What are the building codes or regulations that pertain to exterior cladding, and how do they influence the design and construction process?
Designers are often restricted with codes in their design. No, as they know, these limitations ultimately benefit both the users and the environment. That does matter!
The construction industry’s focus on sustainable cladding materials drives building performance enhancement. Building codes act as the backbone guideline of these standards, ensuring that the building enclosure is of high quality and meets efficiency guidelines. Designers must adhere to these codes when selecting materials, system components, layer sequencing, durability, insulation procedures, loads, testing, heat-moisture-air flow, and acoustic.
Today, most codes demand environmentally friendly and cost-effective sustainable cladding materials. This results in an iterative design process that meets the code requirements, boosts performance and achieves certification goals while maintaining the client’s desired business aesthetic for the building façades. In the USA, each state has its own set of regulations in the code. In the Middle East, international codes are used alongside the current codes of each country to choose materials with better qualities and safe loads.
Some of the codes used for façades and cladding systems include ANSI/ASA-EN1808 for acoustics, NFPA 285 for fire resistance, NFRC100/200 for thermal transmittance/loads, NIBS/ASHARE for building energy-efficient heat and airflow, ASTM E119 for water tightness, AAMA for fire performance, IBC for structural wind loads, and IRC.
In terms of cost-effectiveness, how does the initial investment in high-quality exterior cladding materials compare to potential long-term savings in maintenance and energy efficiency?
It’s a fact that investing money in high-quality cladding is a serious matter, and clients must be increasingly aware of the importance of returning it. By opting for high-performance cladding materials and their specialised system components, like insulation, cavities, flashing, and WRB, coupled with a rain screen substructure, you can save money in the long term and contribute to preserving the environment.
A careful selection of high-quality cladding materials coupled with skilled installation techniques can lead to significant savings. Incorporating Nanotechnology into cladding materials presents significant advantages, including the possibility of creating self-cleaning surfaces, reducing the need for cleaning using traditional methods, and ultimately saving costs.
Moreover, one can generate energy by integrating photovoltaic technology, further enhancing the cost-saving benefits of such cladding systems. Replacing conventional reinforced concrete cladding with ultra-high performance fiber reinforced concrete (UHPFRC) can reduce the embodied carbon of precast concrete façade cladding by up to 50%. Additionally, ETFE cushions can be employed as an alternative to triple-glazing claddings, further contributing to energy savings. Similarly, using bio-based insulation materials derived from renewable sources can dramatically reduce thermal loads in buildings while carrying a low embodied energy, thus cutting down on energy consumption.
One noteworthy example of a bio-based material is date palm fiber insulation, which boasts the lowest life cycle energy balance of all building materials, surpassing expanded polystyrene and glass wool insulation. Finally, consider informed decisions concerning the aspects of multiple cladding systems’ thicknesses, joints, corners, and finishing such as a gradient mix of colours and patterns on one panel, and a mix of materials. All of these are essential when designing a building envelope assembly. These components are interdependent and should function harmoniously for a successful design that matches the desires of multiple tenants and commercial rentals that will last for years. To achieve this, reviewing data sheets and conducting thorough analyses of each option’s benefits and potential returns is crucial. Simplifying this information can help build client trust and develop strong, long-term relationships. This approach can positively impact the built environment and contribute to a brighter future.
Senior Façade Engineer, Building Envelope Specialist
Maha Al-Gebaly is an enthusiast façade Engineer in the building envelope industry that has graduated from the Faculty of Engineering, Alexandria University. Maha AL-Gebaly has worked for façade department flexibly within experienced cross-functional teams at multinational leading firms headquartered in the UK (Lindner facades-Lindner prater ltd), China (CSCEC-China state construction Engineering corporation), UAE (AESGAlabbar Energy & Sustainability Group), and Egypt (Alutec-The Egyptian German Aluminum Company) on projects throughout the Middle East |GCC such as Zayed National Museum (Norman Foster and WSP), The Island MGM, Bellagio, & Aria Hotels (UN studio and Brewer Smith Brewer Group), Cairo festival city living (Al-Futtaim development), and Alamein iconic tower (DAR). Her area of interest focused on creating impactful advanced design solutions that can get the world we live in ready for the future.