Why stainless steel façades contribute to architectural sustainability - Our reflections

In response, architecture, engineering, and construction (AEC) stakeholders are under growing pressure from regulators and clients to reduce the full life cycle emissions of materials used in the built environment. What a building will look like on the outside is now firmly intertwined with how it will perform as a physical, financial, and even ethical object. 

While decarbonizing the industry will not be achieved by one solution alone, advancements in materials science and life cycle assessment have enabled practitioners to target key areas with precision. Stainless steel, when specified appropriately in demanding façade applications, offers a combination of durability, corrosion resistance, and recyclability that aligns well with growing requirements for service-life longevity and circularity. 

In this article we examine how stainless steel façades can contribute to greater sustainability in the built environment, while providing realistic assessments of their role, capabilities, and limitations within the broader drive to lower the sector's carbon footprint. 

The pressure to reduce carbon across the building sector 

The built environment is a key focus of new sustainability legislation around the world. In Europe, the implementation of the EU Green Deal includes the updated Energy Performance of Buildings Directive and the Corporate Sustainability Reporting Directive (CSRD), both of which bring embodied emissions into regulatory scope.  

In the United States, initiatives such as Buy Clean California are enforcing carbon reporting for construction materials purchased with public funds.² In parallel, global frameworks such as the EU Taxonomy, LEED, BREEAM, and other green building certification systems can influence developer decision-making.³ 

All of these mechanisms direct attention not only toward operational energy use but also to the trillion-dollar question of “how long.” The longer a high-emission material remains in use, the lower its annualized impact. Short-life low-cost materials that require frequent replacement or repainting represent a hidden emissions burden. Reducing this burden requires not only low-emissions materials, but ones which will stand the test of time.

Stainless steel for façades: where does it make sense? 

Stainless steel is not widely used across structural construction due to its upfront cost, as well as architects’ and fabricators’ lack of familiarity with the material compared to concrete or carbon steel. However, in targeted exterior envelope applications where mechanical and visual longevity is a requirement, stainless steel can add significant value. These are typically high-profile and high-budget projects where architectural finish retention has been deemed vital.

Using stainless steel here provides two specific sustainability-oriented benefits: 

• Extended service life with minimal degradation 
• Avoidance of protective coating systems (paints, lacquers) and their maintenance cycles 

Notably, stainless steel use in façades is still reflective of a niche high-performance market rather than a broad building-level solution. Its contribution to improving the entire carbon footprint of a building is limited in percentage terms but meaningful in  durability terms.

One of stainless steel’s greatest strengths is its natural resistance to rust, corrosion, and weathering, particularly in harsh urban or coastal environments if the appropriate grade has been selected. Unlike other materials that require the application of protective coatings, repainting, or frequent maintenance, stainless steel gains its properties from the microscopically thin oxide film that forms on its surface. And if scratched, this film will self-heal. This means buildings retain their original look and structural performance virtually forever, reducing both long-term costs and environmental impact.

The performance characteristics that distinguish stainless steel for façade cladding include:

Corrosion resistance

This is the defining feature of stainless steel, and varies significantly by grade.  In austenitic grades such as 316L (Supra 316L/4404), added molybdenum enhances this protection in marine or urban environments.⁴ Duplex grades (e.g., Forta DX 2205) combine austenitic and ferritic microstructures for higher mechanical strength and corrosion resistance, although their use remains limited in façade applications due to forming demands.

Recyclability and recycled content   

When produced with scrap, stainless steel has a high recyclability rate and does not degrade with repeated use. Outokumpu’s Circle Green stainless steel — as well as having eliminated 95% of all scope 1 and 2 CO2 emissions by using only renewable sources and low-carbon electricity for production — has an industry-leading recycled content of over 90%, and up carbon footprint as low as 7% of the global average. This is a major driver for its low Scope 3 emissions. Outokumpu’s overall carbon footprint is 75% lower than industry average.⁵

Flatness and optical uniformity 

For large façades with repeating cladding elements, visual consistency is essential. Surface finishes such as Deco Linen require tight quality control to avoid visible pattern or hue variation across panels. Mechanical processing such as stretch-leveling and tension-leveling are crucial factors in producing material that meets architectural expectations.

Color stability   

Unlike coated metals, stainless steel finishes do not rely on brittle paint systems that peel or chalk over time. Color or tone is achieved through surface structuring (e.g., embossing or blasting) or via physical modifications like electrochemical coloring.⁶ When properly applied, these are permanent solutions that require no reapplication over decades. 

Grade selection based on environmental corrosivity 

Environmental conditions should determine the grade of stainless steel specified for a façade project. ISO 9223 categorizes outdoor environments into corrosivity classes (C1 to CX), with grades recommended as follows:⁷ 

• C1–C2 (Very low–Low): Typical grades include 1.4016 (430), 1.4301 (304) 
• C3 (Medium): Supra 316L/4404 becomes appropriate 
• C4–C5 (High–Very High): Duplex grades such as Forta DX 2205 or even Ultra 904L (1.4539) are recommended 
• CX (Extreme): Super-austenitic grades like Ultra 254 SMO® or Forta SDX 2507 are required 

Misalignment between environment and grade can result in corrosion phenomena such as pitting and tea staining, especially in coastal regions with salt spray or in cities with poor air quality.⁸ 

Embodied carbon: understanding emission profiles

Embodied carbon in stainless steel varies based on input materials and production methods. At Outokumpu, production using Electric Arc Furnaces (EAF) combined with 90% low-carbon electricity of our electricity mix globally results in an average product carbon footprint of approximately 1.6 kg CO₂e per kg of stainless steel based on lifecycle assessment, well below European and global averages.⁹ 

Circle Green further reduces this footprint to below 1 t CO₂/t, achieved by using: 

• Biobased fuels (biogas, bio-coke) 
• 100% low-carbon electricity 
• Up to 100% use of low-emission raw materials such as scrap 

For comparison (industry averages):¹⁰ 

• Stainless steel: 3.0–4.0 kg CO₂/kg 
• Aluminum: 10–12 kg CO₂/kg 
• Concrete: 0.5–1.0 kg CO₂/kg 

While stainless steel has a higher per-kilogram footprint than concrete, its superior circularity, and higher durability — especially in exposed applications — offers better long-term amortization when considered over a service life of 75–100+ years. 

Façades are not structures: a realistic impact assessment 

Stainless steel, due to cost and density, is unlikely to replace concrete or carbon steel for superstructure components in most buildings. Thus, its contribution to reducing a building’s overall embodied carbon is modest,  and limited primarily to the envelope. 

However, façades play a role disproportionate to their volume when considering: 

• Thermal performance (when combined with insulation) 
• Aesthetic and brand value 
• Maintenance-related emissions 
• Weather resistance and building integrity (resilience) 

In urban contexts, the reflective properties of properly finished stainless steel can mitigate solar heat gain and aid in urban heat island reduction.¹¹ Patterned surfaces like Deco Linen or the industrially shot blasted finish Deco Supermatt also offer lower glare compared to mirror-polished or plain BA/2R material, meeting increasing regulation in solar reflectance values (e.g., Singapore). 

Future potential: data and decarbonization 

New product-specific emissions reporting is helping stainless steel compete in a carbon-budget-constrained environment. Outokumpu now provides a product-specific carbon footprint listed on each delivery certificate, calculated in line with ISO 14067 and verified by WSP. 

This enables: 

• More accurate reporting for sustainability certifications 
• Better lifecycle modeling in whole-building assessments 
• Data-aligned procurement for green public procurement and ESG investors 

In the coming years, as decarbonization regulations tighten and materials accountability increases, especially for Scope 3 emissions and beyond, having carbon data readily available will become a procurement standard. 

Contribution within bounded contexts 

Stainless steel is not an all-purpose emissions solution. Rather, its power lies in specific applications — most notably in façades where corrosion resistance, visual consistency, and long-term durability are essential. 

When the appropriate grade is specified for the environmental conditions, and when produced using high-recycled-content, low-emissions processes, stainless steel façades can: 

• Extend service life well beyond typical coating systems 
• Reduce recurring maintenance (except for regular cleaning) and associated emissions 
• Provide permanent finishes without needing reapplication 
• Contribute credible data toward Scope 3 GHG accounting 

As low-carbon electricity grids expand and metallurgical emissions are further reduced through material innovation and circular economy practices, stainless steel’s attractiveness for façade design will likely grow. This will not come as a universal solution to carbon reduction, but as a tactical contribution in the pursuit of long-life, zero-maintenance and performance-oriented architecture. 

Citations: 

1. Global Status Report 2019, Global Alliance for Buildings and Construction (IEA & UNEP)   
2. Buy Clean California Act (2017), State of California   
3. European Green Deal, EU Commission   
4. Outokumpu Façade design Guide (2023)   
5. Outokumpu Yearly Report 2024 (2025)   
6. INOX-SPECTRAL® Coloring, Inox-Color GmbH   
7. ISO 9223 Corrosivity of Atmospheres   
8. IMOA (International Molybdenum Association) façade corrosion guide   
9. Outokumpu – Environment (2024) 
10. World Steel Association, Metal Production Benchmarks (2022) 
11. Urban Heat Island Effect Solutions and Funding, National League of Cities (2023)