As a major driver of natural resource consumption, energy use, and greenhouse gas emissions, the construction industry has a significant impact on the environment, consuming 32% of global energy and contributing to 34% of global CO₂ emissions. Building materials play a crucial role in shaping the built environment. Through principles of circular economy, renewable and self-sufficient solutions, and technological innovations, analyzing the environmental performance of each material highlights the opportunity to review and assess the different stages of its life cycle.

By establishing a common framework for measuring and managing the environmental impact of building materials, Life Cycle Assessment (LCA) emerges as a key approach. This methodology provides a comprehensive evaluation of the environmental impacts associated with products, processes, or activities throughout their entire life cycle. From raw material extraction, manufacturing, and transportation to construction, use, and end-of-life treatment, the analysis considers the environmental burdens linked to each stage. In the context of building materials, LCA offers a holistic and systematic approach to assessing environmental performance and identifying opportunities for design optimization, among other improvements. In this way, it quantifies impacts such as carbon emissions, energy consumption, water use, air pollution, waste generation, and ecosystem depletion.

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Exhibitions can be an opportunity to extend architectural discourse beyond professional circles, opening conversations with broader publics and serving as an interface between architecture and society. Within this concept, major international events such as the Osaka International Expo 2025 and the Venice Architecture Biennale have adopted the idea of the circular economy as one of their organizational objectives. The idea of circularity in events can be reflected in, for example, their energy consumption, the impact of the displacement they generate, their waste, or the useful life of their infrastructure. The site destined for the last World Expo, held in Osaka from 13 April to 13 October 2025, was surrounded by a massive timber structure designed by Sou Fujimoto Architects, one of the world's largest wooden constructions. The Japan Association for the 2025 World Exposition committed to reusing building materials "as much as possible," with concrete plans for their reuse to be finalized by March. In the meantime, some relocation alternatives are already emerging for the pieces of the World Expo structure.

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The 2025 Osaka Expo has captured widespread attention—not only for its architectural ambition and spectacle, but also for breaking records and generating controversy. Its most iconic feature, a monumental timber ring designed by Sou Fujimoto, has already made headlines as a Guinness World Record-breaking wooden structure. Built on the reclaimed island of Yumeshima, the site has attracted praise and critique in equal measure. Beyond its awe-inspiring 2-kilometer circumference—parts of which extend dramatically over the water—the structure has also drawn concerns, including questions about health & safety, extreme heat, and swarms of insects that may affect the visitor experience.

This year also marks a significant anniversary: the 55th year since the 1970 Osaka Expo, held under drastically different socio-economic conditions. Comparing these two expos—both hosted in the same city—offers a rare opportunity to reflect on how the rhetoric, curatorial themes, and architectural ambitions of world expos have evolved over time. From "Progress and Harmony for Mankind" in 1970 to "Designing Future Society for Our Lives" in 2025, the shift in thematic focus reveals changing global priorities. Meanwhile, the scale and nature of architectural involvement have also transformed, from the futuristic visions of Japanese Metabolism to a more internationally dispersed group of designers concerned with sustainability, technology, and civic engagement.

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