An analysis of heat insulation efficiency of building outer skins used for green building

In general, the poor thermal insulation of building materials usually causes elevated room temperature, which not only reduces the comfort of the environment but also adds extra loading to the air conditioner. The objective of this study is to investigate the heat insulation efficiencies of building outer skins used for green building. A total of 25 types of multi-layer cladding materials and 9 types of single-layer skin materials made in Taiwan along with 4 types of overseas multi-layer skin materials were tested using the hot box method (HBM). The above data were then adopted to calculate the heat-insulation ability, vapor transmission volume and heat gain cooling load. Besides, the costs of the above materials were also collected to provide useful information for green building industry to select the most proper skin materials in considering both the material performance and costs. The analysis results suggest that the ‘k’ group (paint-baked metal plate + 2” 100 k rock wool + paint-baked metal plate) exhibits the best heat-insulating capacity, which is 67.0%. However, Item 15 (colour corrugated steel plate + conventional steel bearing plate + calcium silicate board) presents the smallest moisture-permeable amount at 0.001 g/h. Besides, Item ‘13’ exhibits the smallest cooling load, which is 1.8 W. From the above, it is shown that superior heat-insulating performance does not necessarily mean better moisture permeability resistance. The skin material which presents superior moisture permeability resistance does not always present a higher cooling load. For this reason, the appropriate skin materials should be selected by matching with the climatic environment where the building is located. Moreover, the decrement of CO₂ emissions caused by transportation is also another key point which the green building industry should consider.

Practical application: The objectives of this research are to investigate the heat insulation efficiencies of building outer skins used in the green buildings. The heat capacity, moisture-permeable resistance, solar heat gain cooling load and costs of the building outer skins frequently used in Taiwan have been calculated and collected in this study. Therefore, the engineers and building industry can choose the most suitable materials with the help of the above information.