Procedures for estimation of insulation thickness for surface temperature control of low- and high-temperature vertical wall has been investigated. Design logic for insulation thickness was generalized into a simple dimensionless equation. For the case of condensation control, Bi takes a relatively large value of 8, indicating that the insulation material side controls the transport processes, while the case of personnel protection requires a correct understanding of the surface phenomena. Insulation thickness increases drastically with surface emissivity for the former case and vice versa for the latter. Adequate revision of official technical data to include new material and development of finishing material has been also suggested.