How to Determine Heating-cable Insulation Thickness

Base thickness on a heat-loss calculation from medium temperature, local minimum ambient and the maintain temperature, then back-calculate the economic thickness from the insulation's conductivity. Thicker is not always better. For outdoor pipes add a weatherproof jacket (aluminum sheet, galvanized or stainless steel) to stop rain ingress. Follow national standard atlases or ask the maker for a thermal calculation.