Sustainable facade materials: Ultimate guide to reducing carbon footprint in construction

A building’s facade acts as its primary interface with the external environment, so consequently, it plays a critical role in both its aesthetic appeal and its environmental performance. As the architecture, engineering, and construction (AEC) industry grapples with its significant contribution to global carbon emissions, the industry has, in response, intensified its focus on sustainable facade design. Furthermore, the growing demand for green buildings and sustainable architecture actively spurs innovation in materials that minimise environmental impact. The selection of sustainable and green facade materials for design and building solutions profoundly affects a building’s thermal performance, energy consumption, and overall carbon footprint. Therefore, a technical analysis of these materials from a sustainable standpoint is essential for future-proof construction.

Environmental impact of a facade system

The environmental impact of a facade system is twofold. First, it encompasses the embodied carbon associated with manufacturing and transporting materials. Second, it includes the operational carbon related to the building’s energy use for heating, cooling, and lighting. For instance, materials with high thermal resistance and shading capabilities can significantly reduce a building’s energy demands. In addition, the choice of locally sourced, recycled, or renewable materials can drastically lower its embodied carbon.

Image source: materialsassemble.com

What makes a facade material sustainable?

Architects and engineers evaluate a truly sustainable facade material against a comprehensive set of criteria that extend beyond mere recycled content. From a technical perspective, the following attributes are paramount:

Durability and weather resistance

A long service life, for example, reduces the need for replacements, thereby minimising resource consumption over the building’s lifespan. Materials that actively resist moisture, UV radiation, pests, and fire contribute to a lower life cycle cost and environmental impact.

Thermal insulation and shading capabilities

The thermal performance of a facade is a key determinant of a building’s energy efficiency. Specifically, materials with low thermal conductivity (U-value) and the ability to provide effective shading reduce the reliance on mechanical heating and cooling systems.

Local availability and recyclability

Sourcing materials locally minimises transportation-related emissions. Furthermore, the ability to recycle or reuse materials at the end of their life is crucial for achieving a circular economy in construction.

Embodied energy and life cycle carbon footprint

This metric quantifies the total energy a material consumes and the greenhouse gases it emits during its entire life cycle, from raw materials to disposal.

Non-toxicity and VOC emission

Above all, sustainable materials should not release harmful Volatile Organic Compounds (VOCs) that can compromise Indoor Air Quality (IAQ) and the health of the residents. Emission rates, therefore, are a critical factor in material selection.

Sustainable materials in facade systems

The palette of sustainable facade materials is diverse, encompassing natural, recycled, engineered, and smart materials for green facade building design and solutions. Each category, moreover, offers unique technical advantages and aesthetic possibilities for innovative green facade design.

Naturals & renewable materials

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These materials originate from natural sources that nature can replenish over a relatively short period.

• Bamboo: Bamboo, a rapidly renewable resource, reaches maturity for harvest in just 3-5 years. Engineered bamboo cladding offers a durable and aesthetically pleasing facade solution.
• Cork: Harvesters take cork from the bark of cork oak trees, making it a renewable and biodegradable material. Expanded cork boards, as a result, provide excellent thermal and acoustic insulation.
• Hempcrete: Hempcrete is a carbon-negative material created from hemp hurd and lime. In fact, it provides excellent thermal insulating properties, with a thermal conductivity typically ranging from 0.06 to 0.07 W/mK.
• Straw bales: Straw bales are a highly insulating and low-cost agricultural byproduct. They can create thick, energy-efficient walls. While not a conventional sustainable facade material in modern high-rise building, they certainly are a viable option for low-rise structures.
• Rammed earth: This technique involves compacting a mixture of soil, clay, sand, and a stabiliser to create durable and monolithic walls. Notably, rammed earth has excellent thermal mass which helps regulate indoor temperatures.

Image source: materialsassemble.com

Recycled & reclaimed materials

The use of recycled and reclaimed sustainable facade materials for green building, design, and solutions diverts waste from landfills and, at the same time, reduces the demand for virgin resources.

• Recycled wood: Builders can reproduce reclaimed timber from old buildings or industrial sources for facade cladding, which offers a rustic aesthetic with a low carbon footprint.
• Recycled steel: Steel can be recycled without any loss of quality, and using recycled steel can significantly reduce a facade’s embodied energy. Recycling steel uses approximately 75% less energy than producing it from raw materials.
• Recycled aluminium: Aluminium, like steel, can be recycled over and over without any loss of quality. LCA (Life Cycle Assessments) are crucial for understanding the environmental benefits of using recycled aluminium in facades. Tostem India provides sophisticated architectural facade systems.
• Recycled plastics: Composite panels made from recycled plastics, such as high-density polyethylene (HDPE), and wood fibres offer a durable and low maintenance alternative to traditional wood cladding.
• Recycled glass: Manufacturers can incorporate crushed and recycled glass into facade panels, offering unique aesthetic possibilities. These panels can provide both visual appeal and functional benefits like light diffusion.
• Recycled ceramics: The ceramics industry can repurpose its waste into new facade tiles and panels, thus reducing landfill waste.

Engineered & composite materials

These sustainability facade materials are produced to achieve specific performance characteristics, often combining different components to enhance strength, durability, and sustainability.

• Fibre cement boards: Composed of cement, cellulose fibres, and water, fibre cement boards are durable and have a long service life of 30 to 50 years or more. They are non-combustible and can be recycled in some facilities.
• High pressure laminates: HPL panels are created from layers of raisin impregnated paper bonded under high-pressure. HPL manufacturers like Greenlam Laminates provide help in reducing the carbon footprint.
• Terracotta panels: Made from natural clay, terracotta is a durable and long-lasting facade material with a relatively low carbon output. Designers can use it in rainscreen systems to improve a building’s thermal performance. Sintered stone panels like the Stonelam Elegante 3mm Series offer a sophisticated alternative.
• Composite wood-plastic panels: These panels combine wood fibres with recycled plastics to create a material that is both aesthetically pleasing and highly resistant to moisture and pests. Many WPC products are composed of a high percentage of recycled materials. As an alternative, solid polymer cladding systems, such as the Vox Malt Oak Fourfold Panel, use advanced printing and texturing on a polymer base to offer a hyper-realistic wood look with high durability and virtually zero maintenance.
• Engineered timber: Canadian Wood is actively developing India’s market for engineered timber, promoting high-performance products like glulam and CLT sourced from British Columbia’s certified, sustainably managed forests.

Smart & hybrid materials

These materials and systems actively respond to environmental conditions to optimise a building performance, representing the cutting edge of green facade design and solutions.

• Double skin facade: the system consists of two layers of glazing with an intermediate air cavity. The cavity, which can be naturally or mechanically ventilated, acts as a thermal buffer. As a result, it reduces heat gain in the summer and heat loss in the winter.
• Green facade: Green facades are also known as living walls. They cover a building’s exterior with vegetation. They provide excellent thermal insulation, improve air quality, and additionally, enhance biodiversity.
• Building integrated photovoltaics: BIPV systems integrate photovoltaic cells into the building envelope, such as in class panels or roofing materials, to generate electricity on site.
• Vacuum insulated panels: VIPs consist of a rigid core under a vacuum, enclosed in a glass tight envelope. They offer extremely high levels of thermal resistance.

Image source: materialsassemble.com

Glazing & transparent materials

Advancements in glazing technology have led to products that offer both transparency and high thermal performance.

• Low-e glass: Low-e glass has a microscopic coating that reflects thermal radiation, consequently, it reduces heat transfer. Manufacturers like aluplast and Fenesta make high-quality uPVC windows with low-e glass that are perfect for the weather in India.
• Double/triple glazing: Multiple panes of glass with an insulating gas filled cavity between them significantly improve thermal performance compared to single glazing. A leading example available in the market is Saint-Gobain’s COOL-LITE XTREME 70/33 II.
• Photovoltaic glass: This technology integrates transparent photovoltaic cells into glass panels. This allows them to generate electricity while still admitting natural light.

Limitations of sustainable materials in facade systems

However, despite the numerous benefits, sustainable facade materials and green facade design and solutions present several challenges.

• Higher initial cost: Many sustainable materials demand a higher upfront cost compared to their conventional counterparts. Nevertheless, long-term savings in energy consumption and maintenance can often offset the initial costs.
• Technical performance gaps: Some natural materials cannot offer the same level of structural strength or fire resistance as conventional materials. This, in turn, may require additional treatment or structural support.
• Limited availability: Certain sustainable materials may not be readily available in all regions. They can subsequently lead to increased transportation costs and a much larger carbon footprint.
• Complex installation and maintenance: Some sustainable facade systems, like green facades, require specialised installation and ongoing maintenance to ensure their performance and longevity.
• Aesthetic and structural limitations: The aesthetic qualities of some sustainable materials may not align with all architectural styles. Additionally, their structural properties may limit their use in high-rise buildings.

Ultimately, the selection of facade materials is a critical decision in the pursuit of sustainable building facades. From natural and renewable materials that offer a low-carbon alternative to traditional options, to advanced smart materials that actively manage a building’s energy use, the possibilities for creating sustainable and high-performing facades are continuously expanding. Therefore, by prioritising materials with low embodied carbon, excellent thermal performance, and a long circular life-cycle, the AEC industry can significantly reduce the environmental footprint of the built environment and create a more sustainable future.

FAQs

How do facade materials influence a building’s overall carbon footprint?

First, facade materials influence a building’s carbon footprint through their embodied carbon, which accounts for emissions from manufacturing and transport. Second, their thermal performance dictates operational carbon from heating and cooling. Therefore, selecting materials with low embodied carbon and high insulation significantly reduces a building’s lifelong carbon emissions, which is a core tenet of sustainable facade design.

How can facade material selection influence a building’s adaptability to future climate scenarios?

Choosing durable and weather resistant materials is crucial for adapting to future climate scenarios that may include more extreme weather events. In addition, facade systems that provide excellent thermal insulation and solar control will be vital in mitigating rising temperatures. As a result, this reduces the reliance on energy intensive cooling systems and enhances the building’s overall resilience.

What are the ethical implications of sourcing sustainable materials in facade systems?

Ethical sourcing of sustainable materials involves ensuring that processes do not harm ecosystems or exploit labour. For example, this includes using certified wood from responsibly managed forests and ensuring fair labour practices in raw material extraction. Furthermore, promoting the use of recycled materials reduces the environmental and social impacts of continued resource extraction.

Do sustainable materials in facade systems perform well in extreme climates?

Indeed, many sustainable facade materials perform exceptionally well in extreme climates. For instance, materials with high thermal mass like rammed earth are excellent for hot, arid climates. Conversely, highly insulating materials hempcrete and vacuum insulated panels are ideal for very cold climates. The key, therefore, is to select a material with the appropriate thermal properties for the specific climate.

Can traditional materials like mud, brick, or bamboo be used in modern facade systems?

Yes, designers are increasingly integrating traditional materials into facade systems. For example, they now use engineered bamboo and contemporary rainscreen cladding. While builders have used traditional mud and brick for centuries, modern techniques can enhance their performance and durability by using contemporary designs, often in combination with other advanced materials to create green facade design and solutions.

*The featured image used in this article is from materialsassemble.com

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