A drying appliance includes an outer cabinet having a back panel. A rotating drum is positioned adjacent to an arcuate recess of the back panel. A blower delivers process air through an airflow path that includes the rotating drum. The airflow path extends through an airway defined within the arcuate recess of the back panel and through a rear wall of the drum. An insulation panel is positioned between the rear wall of the drum and the back panel of the outer cabinet. The insulation panel occupies the arcuate recess and partially surrounds the airway to prevent accumulation of lint within the arcuate recess. The insulation panel is configured to prevent thermal transfer from a processing space within the rotating drum and an area rearward of the back panel.