Reusing exterior wall framing systems: A cradle-to-cradle comparative life cycle assessment

Area of Science:

• Construction Industry
• Circular Economy
• Life Cycle Assessment (LCA)

Background:

• The construction sector is a major consumer of global resources and a significant generator of waste.
• Circular economy principles promote component reuse to enhance resource efficiency and minimize waste.
• The environmental viability of reusing high-embodied energy materials like steel in construction requires investigation.

Purpose of the Study:

• To compare the environmental impacts of a single-use wood-framed wall versus a reusable steel-framed wall in a U.S. tiny house.
• To determine the conditions under which reusing high-embodied energy materials can offset their environmental footprint.
• To assess the influence of different LCA methodologies on cradle-to-cradle (C2C) assessments.

Main Methods:

• Utilized two distinct life cycle assessment (LCA) methods: process-based and hybrid LCA.
• Analyzed global warming potential, embodied energy, and water use as key impact categories.
• Modeled a comparative scenario of a single-use wood wall and a reusable steel wall for a tiny house.

Main Results:

• Significant reuse benefits for steel framing were observed only at aggressive reuse rates exceeding 70%.
• Multiple reuses of steel components were necessary to compensate for the initial embodied environmental impacts of steel production.
• Conflicting outcomes in C2C LCA were identified between process-based and hybrid LCA methods.

Conclusions:

• The environmental advantages of reusing steel framing are contingent upon achieving high reuse rates and multiple lifecycles.
• The choice of LCA methodology can substantially affect the interpretation of C2C environmental performance.
• Further research is needed to refine LCA approaches for circular economy assessments in construction.