Heating Scottish public buildings with low temperature heat networks: An investigation

Heat generation accounts for approximately half of the UK's final energy consumption, and its decarbonisation is yet to happen. A major step towards this goal will be phasing out natural gas, which is set to be replaced primarily by heat pumps and low-temperature heat networks for building heating. These technologies operate efficiently at reduced temperatures, typically 55/25°C (supply/return), whereas most UK buildings have been designed for 82/71°C. With 80% of existing buildings expected to still be in use by 2050, this raises the question of their ability to use reduced temperature heat. This thesis is the first to explore the feasibility of this temperature transition, drawing on the experiences of Sweden and Denmark, and offering insights into how these lessons can be applied to the UK. The literature review also provides recommendations for policymakers. The scope of this thesis is focused on the study of Scottish Public buildings. The methodology relies on empirical data provided by Scottish local authorities, complemented by a pre-1919 school building case study. The findings indicate that when buildings are classified by the proposed age groups, the performance gap shows an increasing trend of over the years, with a steady increase since 1945. They have also shown that the renovation of a building envelope is not a pre-requisite for using low-temperature heat in pre- 1980 constructed buildings. The pre-1919 case study highlights that an oversizing of 32% has been evaluated on installed space heating capacity, and this enables a reduction of the supply temperature below 70°C all year round. In addition, it shows that flow temperature can always be maintained below 55°C during daytime due to internal heat gains. It can be concluded that such a pre-1919 school building presents a nascent readiness for low-temperature heat. This thesis provides an important contribution to knowledge. While it does not diminish the benefits of applying fabric upgrade measures, it offers evidence that decarbonisation strategies can be flexible. Specifically, energy efficiency measures and the development of low-carbon heating can be considered in parallel. Further work is necessary to determine whether a similar trend can be observed across the entire pre-1919 age group and potentially extended to the broader building stock.