Towards low flow temperatures: Making buildings ready for heat pumps and modern district heating


Following the fossil gas crisis, saving energy used for heating has become a priority for many households, companies, and governments. At the same time, many European countries are in the process of introducing policies to shift from heating oil and gas as well as fossil fuel-based district heating to clean and renewable heat as part of their decarbonisation agendas.

A key element in saving energy from heating and facilitating the introduction of clean heat sources is to increase the use of low flow temperatures in heating systems. Typically, heating systems in Europe use water flowing through pipes and emitters (radiators) heated to high temperatures (70-90°C). This is the flow temperature. Reducing this flow temperature, while ensuring required internal temperatures can still be met, enables heat pumps, solar thermal collectors, condensing boilers and district heating systems to run more efficiently and on renewable energy.

The study “Towards low flow temperatures: Making buildings ready for heat pumps and modern district heating” describes how a ‘low flow temperature ready’ (LT ready) concept can be an important tool to ensure buildings can be heated efficiently, particularly with clean heat.

This study, explores the benefits of heating with low(er) flow temperature water for different heating technologies, focussing on heat pumps and district heating, the barriers to reducing flow temperatures in heating systems and examines the concept of LT readiness and its limitations by discussing how to make a building LT ready. This concept will be explored in two case studies. The first case study looks at LT readiness from the perspective of individual buildings. For four typical German buildings, we calculate the required steps to make them LT ready and propose a ‘procedure’ to renovate them. The second case study looks at a German city that plans to develop a low temperature district heating system and make 400 buildings LT ready. Last the study explores how LT readiness can be implemented through a range of policy tools and provides a short inventory of policies that address low temperature heating and LT readiness.


September 2022 – June 2023


European Climate Foundation


Regulatory Assistance Project (RAP)



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