Evaluations On Economical And Environmental Benefits Of Thermal Insulation Materials On Exterior-wall During Life Cycle

Exterior wall is an important part of building envelope, the thermal insulation performance of which is particularly important to control the energy consumption of building envelope, which is the focus of the energy saving design. However, for a long time, the materials of most exterior walls are simply concrete or ordinary bricks with poor thermal insulation performance, which cannot meet the specification and provision of building energy-saving design. Therefore, new techniques and products of thermal insulation have become one of the main energy-saving techniques that attracts most attentions in building energy-saving. As an important mean to reduce thermo condution and improve heat efficiency, the economic efficiency and environmental impacts of thermal insulation material in building throughout its life cycle are worth discussing. Based on life cycle theory, combined with the methods of techno-economics and Building Environmental Performance Assessment System(BEPAS), the economical and environmental benefits during the life cycle of thermal insulation materials were studied; with the heat transfer equation, the energy-saving efficiency of EPS, expanded perlite, rock wool and insulation mortar were calculated, and the economical benefits were analyzed with the method of net present value; a weight system which is suitable for Shaanxi Province was established with the latest statistical data; the emission inventories and emission reduction inventories of 4 insulation materials were analyzed, and their positive, negative and comprehensive impacts on environment were also analyzed and compared.The results show that the positive economical benefits are dominant in operational stage of each material with NPV greater than zero. Using thermal insulation material can save coal and electric power, bringing huge economical benefits. Although each material has a certain negative environmental impact, the positive environmental impact brought by emission reduction in operational stage is dominant. As far as negative impact, the value of EPS is the largest, while it of insulation mortar is the smallest; Each material has different kind of negative environmental impacts: EPS causes some water pollution such as eutrophication and toxicity, but it is a rather low carbon material; expanded perlite discharges huge amount of greenhouse gases during every stage of its life cycle, leading to global warming problem; rock wool creates global warming and solid waste problem, due to its emissions of a large amount of greenhouse gases in its manufacture stage and a mass of waste rock wool fiber in its abandonment stage; the fluoride generated during the manufacture stage of insulation mortar causes the problem of ozone depletion, and insulation mortar also causes global warming; Each material has a huge or some negative impact to environment in its manufacture stage, which could be solved by improving manufacture process and reducing pollution emission; the emission of water pollution of EPS during its manufacture and abandonment stages should be minished, and reclaim of waste rock wool fiber is a topic worth discussed.