Study On Performance Of Heat And Moisture In Light Metal Insulating Sandwich Building Envelope

In recent years, as the innovation of the building materials and the furtherdevelopment of the building energy-saving technology, many buildings which are largeand high energy consumption had turned to lightweight and energy efficiency. Lightmetal insulating sandwich building envelope, as one of the typical representative, has agood many advantages such as less dense, superior thermal performance, easy toinstallation and low maintenance cost. It is used more and more frequently.At present, for the fire safety of the large building, inorganic insulating material,like rock wool, is mainly used in the light metal insulating sandwich building envelope.This kind of material has the characteristics of strong moisture absorption; thereforecontrolling vapor penetration becomes the key to this kind of building envelope. It hasimportant practical significance for the research which focused on the heat and moisturetransfer in the light metal insulating sandwich building envelope.In this paper, it focuses on the related issues of the thermal insulation and themoisture transfer of the light metal insulating sandwich building envelope. It used themethod of theoretical research and experiment.Firstly, the article analyzes the structure characteristics of the light metal insulatingsandwich building envelope. Based on related standards and project data, this paperdescribes the mainly materials applied to this kind of building envelope. The typicalstructures are classified into two types as insulation structure and insulationsound-absorbing structure. Compared with the common concrete insulation structure,light metal insulating sandwich building envelope has high thermal resistance and lowthermal inertia, based on which a simplified calculation method of the heat transfer wasproposed.Secondly, this paper focuses on the theoretical research of the performance of theheat and moisture on the light metal insulating sandwich building envelope. This paperclassified the different boundary types into three kinds and put forward thecorresponding controlling strategy for each one. Condition for controlling condenseswithin insulating layer of the airtight and semi-airtight structure was given and.thermalperformance optimization measures were discussed.At the end of this paper, through the experimental verification method, itresearched on the thermal effect in the summer and winter. Using the steady heat transfer testing method in the guarded hot box in winter condition, thermal parametersand humidity were measured for typical light metal insulated construction with differentvapor penetration case. The results showed that the heat flux through specimen withvapor penetration controlled was reduced to1/5of specimen with vapor penetration.Analyzing the correlation between heat transfer coefficient of specimen and averagehumidity of rock wool in different vapor penetration case based on the measured data,an exponential expression was proposed to describe the effect of humidity on thethermal performance of building envelope. The summer experiment result showed thatthe thermal resistance of specimen can increase after using single reflective membranestructure, and increase more after using double reflective membrane structure.