This guidebook was written between 2018 and 2021 by seventeen authors that used approximately 15 000 hours of work within the IEA DHC TS2 annex. The content is based on more than 250 literature references and 165 inspiration initiatives to obtain lower temperatures in buildings and heat distribution networks. The author group wrote 40 internal documents about early implementations of low-temperature district heating. Fifteen of these early implementations are presented in this guidebook.The guidebook contains aggregated information about the main economic drivers for low-temperature district heating. It shows how to obtain lower temperatures in heating systems inside existing and new buildings, as well as in existing and new heat distribution networks. An applied study of a campus system in Darmstadt shows the possibility of reducing temperatures in an existing heat distribution network with rather high temperatures. The competitiveness of low-temperature district heating is explored by analysing business models and heat distribution costs. Early adopters of low-temperature district heating are presented by examples and by identified transition strategies. Five groups of network configurations with fourteen variants are presented to be used for low-temperature district heating. Finally, all 165 identified inspiration initiatives and all 137 locations mentioned are listed.