Vision Energy were commissioned in 2021 to undertake an assessment in conjunction with fabric and mechanical upgrades to multiple blocks on the campus. The works consisted of external wall insulation & installation of heat pump to decarbonise the site and improve carbon emissions. As part of the works the existing mullion structure was to be retained. This detail was reviewed in specific detail and the thermal path reviewed to determine internal temperatures, as well as internal dew point assessments and more to consider the internal gains and heat loss of the overall condensation risk. Dynamic modelling was carried out to establish the impact of proposed improvement works at Colchester Institute (blocks B&D) on moisture build up and condensation risk. The analysis focuses on masonry mullions that are a regular feature throughout the building. Calculations were carried out using two methodologies: • Finite element calculations that can very accurately model heat flow, but are limited to representing a fixed snap shot in time. • Dynamic calculations which can model the rooms across ever-changing weather patterns with a more simplified representation of heat flows. In this case both methods were comparable when calculating the surface temperatures. The following has been concluded from the analysis.