Insulated flexible ducts feature a core, fiberglass insulation, and a vapor barrier jacket to reduce heat loss and condensation in HVAC systems. Uninsulated flexible ducts consist only of the reinforced core, offering a cost-effective, easy-to-install solution for ventilation or areas where temperature change is not a concern. Insulated ducts are designed to maintain air temperature and prevent moisture condensation, typically used for supply and return air. Uninsulated (or non-insulated) ducts are single-layer or multi-layer conduits designed primarily for air transfer without thermal protection.