The budget used for the retrofitting of low energy efficiency equipment in buildings is normally paid after financially considering the internal rate of return and a simple payback period. The environmental view has not been considered typically. One of the overlooked aspects within the energy conservation measures is the managerial cost of hazardous waste from the removed low energy efficiency equipment. LCA (Life Cycle Cost Analysis) is an approach to consider all inventories and impacts, including the costs in the case of LCC (Life Cycle Cost), covering the environmental aspect, particularly hazardous waste, throughout the life cycle from raw material preparation, removal of existing equipment, installation, to the waste disposal. This study will take into account only Hg in fluorescent tubes and CFC in air conditioners as representative of the range of wastes, because it can be emitted during the retrofitting. The LCA result is used for the creation of a conceptual decision making model showing clear components and structures of investment in retrofitting. The preliminary target audiences for this study are almost 1,700 designated buildings (defined in the Royal Decree, containing an installed transformer of more than 1,000 kW or 1,175 kVA annually or consuming energy of more than 20 million MJ since 1995-2004) in Thailand.