As highlighted by Publicly Available Standards (PAS) 2030 and 2035, buildings of traditional construction require special consideration when undertaking energy retrofits, as unintended consequences may arise from changes to the moisture movement through the building fabric. For historic timber-framed buildings, retrofitting replacement infill panels poses the risk that moisture accumulation may result in accelerated decay. Since 2019 the authors have been undertaking monitoring of eight mock-up replacement infill panels, with the initial results reported at ICMB2021 and the full results of the first two years subsequently published. Funding has now been approved for further work. This paper presents the next steps: continued monitoring of the panels and detailed material characterisation to improve simulation and understand durability. Preliminary results will be presented at the conference.