Insulation thickness is a key planning parameter in external thermal insulation composite systems. It is calculated based on the required U-value, the thermal conductivity of the chosen insulation material, and the existing wall construction. Common thicknesses today range from 100 to 200 mm, and can exceed this for low-energy renovation projects. Insufficient thickness leads to inadequate thermal protection and may increase mould risk due to dew point shifting. Conversely, excessive thickness raises structural and fixing requirements for dowels and adhesives. Selecting the correct insulation thickness is part of the energy consultancy process and is the responsibility of the planner.