CO 2 Footprint Calculator for Tensioned Membrane Structures: Bridging EPD Heterogeneity through a Form‐Force‐Carbon Methodology

Abstract Tensioned membrane architecture is frequently promoted as an inherently lightweight, low‐carbon alternative to conventional construction, yet the embodied carbon data needed to substantiate this claim remains fragmented, inconsistently reported and difficult to compare across material systems. Building on the Nohmura Foundation's earlier Lightweight Footprint research, which proposed first industry‐wide target values for PVC, PTFE and ETFE membrane systems, this paper presents the development of a dedicated CO 2 Footprint Calculator for tensioned membrane structures, undertaken by Membrane. Institute in 2026. A central finding of the work is that Environmental Product Declaration (EPD) data for membrane materials cannot be applied uncritically: current EPD values (2023‐2024) for PVC‐polyester membranes (4‐6 kgCO 2 e/m 2 , A1‐A3) diverge substantially from earlier system‐level reference figures, and comparable discrepancies are observed for PTFE‐glass (15‐20 kgCO 2 e/m 2 ) and ETFE cushion systems (30‐60 kgCO 2 e/m 2 , system‐level, class C/D). These gaps make it clear that EPD figures alone, taken at face value, are not a reliable basis for comparing membrane material systems. To address this heterogeneity, the calculator introduces an EPD classification scheme spanning classes A to F, plus a ‘parked’ category for non‐comparable declarations, together with a Form‐Force‐Carbon methodology that links the form‐finding process directly to material quantity and embodied carbon, rather than treating carbon accounting as a separate, downstream exercise performed only after the structural geometry has been fixed. A first internal demonstrator integrates this methodology directly with the Formfinder form‐finding engine via API, allowing carbon estimates to be generated alongside structural form‐finding for a given membrane geometry, within a single iterative workflow rather than as a posthoc calculation carried out once the design is already complete. The paper reports on the current state of this development, including the EPD classification logic, the underlying Form‐Force‐Carbon approach, the Formfinder API integration, and a critical discussion of the methodology's strengths and present limitations ‐ most notably the continuing scarcity and inconsistency of third‐ party verified EPD data for tensioned membrane materials across manufacturers and regions. The work is presented as an interim status report on a calculator that remains under active development, with the explicit aim of inviting discussion within the TensiNet community on EPD comparability, data availability and the broader question of how lifecycle carbon assessment can be embedded into the early‐stage design of tensioned membrane structures, rather than appended at the end of the design process.