Thermal insulation studies for a private residence, built before the enactment of the Thermal Insulation Code in Greece, is described in this paper. Various insulation protection approaches for the same building envelop, which is situated in the city of Kavala in Northern part of Greece, are investigated. A performance comparison of these technical approaches, concerning cost and energy saving issues, is given. The cost estimation is performed as a function of insulation material used, the labour and insurance cost. The energy saving is evaluated by comparing the energy consumption (in kW h) for space heating before and after the application of thermal insulation in the structure envelop. Finally, useful conclusions were also drawn regarding further steps towards the rational use and energy save in newly erected buildings. (C) 2000 Elsevier Science S.A. All rights reserved.