Panel buildings built in the era of the massive prefabrication are still dominating among all apartment building in Slovakia. Panels buildings are criticize for their low design quality, second-rate construction material and shoddy construction practices. After refurbishment, the energy consumption decreased, but we do not know too much information about satisfaction with thermal comfort of inhabitants living there. The objective of the study was to assess indoor environment in panel buildings after refurbishment. The paper discuss about aspects, which influence thermal comfort. The results were analyzed also from the view of energy efficiency of the buildings. For the purpose of evaluation of the thermal environment a questionnaire was created and completed by inhabitants of the group of buildings before and after renovation. The values of real measured energy consumption were obtained from the administrator of the building. The results reveal problems with thermal comfort and shows how strongoccupant's behavior impact to it.