A big amount of final energy in Europe is used in buildings (about 50%). Thermo insulating investments in the building sector can have a great impacton the improvement of the energetic efficiency of buildings and the reduction of the use of final energy in this sector. In the paper there were presented properly modified indicators for the economic assessment of the investments which is based on the thermal insulation of external walls of the building, such as: net present value, profitability indicator and payback period. For the ecological assessment the following indicators were introduced: ecological net present value, ecological indicator of profitability and ecological payback period. LCA technique was used in ecological indicators. For different variants of external walls, sources of heat and thermo insulating materials, the assessment of investments due to economic and ecological indicators was conducted. Ecological payback periods were obtained within 0-6 years. (C) 2012 Elsevier B.V. All rights reserved.