Comparison of Pre-Insulated Steel and PEX Pipes in District Heating Networks: A Life Cycle Assessment

Distribution systems are a main part of district heating (DH) networks, yet their environmental impact is seldom investigated. In this study, a detailed comparison of two main pipe types used in DH networks is conducted, namely pre-insulated steel pipes and cross-linked polyethylene (PEX) pipes. The study introduces the technical characteristics of the pipes and applies a life cycle assessment (LCA) approach to evaluate their environmental performance under a unified functional unit. In addition, scenario analyses were performed to assess the influence of PEX service lifetime and steel recycling rates. The results show that PEX pipes exhibit lower impacts in several categories, including freshwater ecotoxicity (986.35 vs. 2990.1 kg 1,4-DCB-eq) and particulate matter formation (39.0 vs. 69.2 kg PM2.5-eq), mainly due to lower material requirements. However, higher fossil energy use is observed for PEX (9750.7 vs. 7416.3 kg oil-eq). Climate change impacts are comparable between systems under baseline conditions. Scenario analysis indicates that extending the PEX service lifetime from 30 to 50 years reduces climate change impacts by approximately 40%, demonstrating the importance of long-term durability. For steel pipes, increasing recycling rates from 0 % to 80 % reduces freshwater ecotoxicity by ~80 % and material resource use by ~80 %, highlighting the importance of end-of-life modelling. Overall, the results demonstrate that the environmental performance of DH pipes is governed by the combined influence of material selection, service lifetime, and recycling strategy rather than by material choice alone.