Thermo-physical and energy performance of building envelope modified by natural fiber through building information modelling

The insulating capacity of building envelope materials is vital in defining the heating and cooling (H & C) energy demand. A sustainable strategy for conventional envelope materials is hybridi-zation with natural or waste fibers for better thermal performance. Therefore, this study was designed to use natural (bamboo, coconut coir, jute, sisal) and waste (polyester) fibers for modified envelope materials (brick and mortar). Firstly, the influence of fibers on thermo-physical properties of thermal conductivity, bulk density, porosity, water absorption was analyzed for the brick and mortar made of the aforementioned five fibers. As a result, the best fiber type for the insulating performance is determined as coconut and jute for brick and mortar, respectively. Next, the energy performance of an envelope with best fiber modified material was investigated through BIM energy analysis in terms of H & C loads. Simulations were performed for five cases by modifying the three-layer wall assembly and further by varying the brick layer thickness (115 -230 mm), while the mortar thickness was set as 20 mm. Lastly, economic feasibility was assessed by quantifying the payback period for each thickness. Experimental re-sults revealed that the thermal conductivity of the fiber modified brick and mortar was reduced by 18 and 10%, respectively, by virtue of decreased bulk densities and increased porosity and water absorption. It was also found that the thermo-physical properties have a high interde-pendency by correlation matrix analysis. For the peak H & C loads analysis, they were reduced for fiber modified materials by maximum of 15% and 9%, respectively, as compared with the un-modified envelop material. Furthermore, by increasing thickness from 115 to 230 mm the H & C loads were reduced up to 43% and 33%. Consequently, the addition of the natural or waste fibers was economically feasible with short payback periods (12-48 months) even though the volume fraction of fiber was just 1%.