This study delves into retrofitting buildings for energy efficiency in Polish cities, focusing on thermal insulation in mid-rise residential buildings. Through simulations, it explores strategies to reduce energy usage and environmental impact amid climate change uncertainties. Utilizing statistical downscaling, it assesses insulation methods under evolving climates. Initial findings suggest potential insulation thickness reduction over time, emphasizing the need for adaptable strategies. The research stresses continual adaptation in construction practices to confront future climate variations, aiming for sustainable building development. It advocates proactive retrofitting to combat climate change, highlighting the importance of flexible approaches to environmental shifts.