Study On The Evaluation And Durability Of External Themal Insulation System In Building

Building energy efficiency has become the country's major strategic issues, and the External Thermal Insulation System is currently the most widely used building's exterior envelope energy efficiency measures. However, the cracking, shedding problems, especially the durability problems that occurred in actual use of the system, have affected the promotion of its use, so the evaluation on the durability of external thermal insulation system has become a problem that demand prompt solution in the field of building energy efficiency.In this paper, we conduct a research on the analysis of the variation of the cohesive strength of the EPS board thin-plastering external insulation system, external insulation system with rubber powder polyphenyl granule and perfusion polyurethane foam composite external insulation system, via large-scale atmospheric exposure tests, and a comparative analysis of those three systems is presented. Learned from the test results, the heating - refrigeration cycle has a significant influence on the cohesive strength of the first two types of insulation systems, which will speed up the cohesive strength attenuation, while the influence on the last one is relative small. Although the cohesive strength of perfusion polyurethane foam composite external insulation system is the smallest, the downtrend is the slowest. That is, this type of system is not sensitive to the climatic change. So from the long-term use point of view, the system is most firmly.Based on the theory of Finite Element Method (FEM), we employ the commercial software ANSYS to analyze the variation of the thermal stress and displacement of the EPS board thin-plastering external insulation system, and the effect of insulation thickness on insulation is also considered. We found that the thermal stress has a significant influence on this system, the stress concentration always occurred around the windows and in the central part of wall. The maximum displacements are always found in the boundary of the wall, while the displacements in the central part of wall are minimum. Learned from the results, the insulating efficiency of this type of insulation system is quite desirable, and the effect of insulation thickness on insulating efficiency becomes lower when the insulation thickness reaches a certain value. In this paper, a research on the condensation is developed. Based on the research, we have proposed some basic principles to avoid and control the condensation. They are, increase the thermal resistance of exterior protected construction, raise the internal surface temperature and decrease the internal humidity.Cracks in the external thermal insulation system are mainly affected by four factors: the building structures, the structure of external insulating layer, materials and construction technologies. Cavityless external thermal insulation system must have priority, in order to resist the stresses caused by wind load. And the water absorbing capacity of the materials in the external surface should be lower than that of the internal materials. The ventilation property of materials should be better and better from inside to outside and the compatibility of ventilation property of each material should be emphasized. In all, the ranking of the durability of external thermal insulation system is based on large-scale atmospheric exposure tests, temperature field and stress analysis of each part in the insulation system, measurement and micro-study on the properties of insulating materials et.al.