Longevity is the core argument
A material that lasts decades without replacement or repainting has a genuinely lower lifetime environmental impact than materials needing periodic replacement, repainting or refinishing — even accounting for stainless steel's higher initial production footprint.
Recyclability
Stainless steel is fully and repeatedly recyclable without quality loss — scrap steel commonly gets recycled into new stainless products, unlike materials that degrade in quality through recycling cycles.
No ongoing chemical maintenance
Unlike painted materials needing periodic repainting (with associated solvents and waste), stainless steel's maintenance is essentially just cleaning — a smaller ongoing environmental footprint over the building's life.
The honest caveat
Stainless steel production itself is energy-intensive — the environmental case rests specifically on longevity and end-of-life recyclability outweighing that upfront cost over a multi-decade lifespan, not on it being a "green" material in isolation.