PAS 2035 is a comprehensive standard developed by the British Standards Institution (BSI) to ensure a more holistic approach to retrofitting buildings in the UK. The aim of this standard is to provide a framework for the evaluation of current energy consumption, identification of energy-saving opportunities, and implementation of measures that will lead to more energy-efficient buildings. PAS 2035 also mandates that retrofit works should be carried out in line with the requirements of the most recent Building Regulations, which are in place to ensure that buildings are safe, functional, and sustainable. This standard has become increasingly important in the UK due to the government’s target of achieving net-zero carbon emissions by 2050, and it is expected to play a crucial role in achieving this goal.