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a b s t r a c tIn Cameroon, these last centuries, an increase in energy demand for cooling and heating in buildings has been witnessed all over the world. Solutions must be proposed by researchers and specialists of buildings to remedy this situation. In this study, a literature review on the thermal insulation applications to external walls of buildings was presented, and a case was investigated in a tropical wet and hot climate. The economic model including the cost of insulation material and the present value of energy consumption and the cost over a lifetime of 22 years of the building, were used to find the optimum insulation thickness, energy saving, and payback period, for buildings in Cameroon. Materials that extruded polystyrene were chosen and used for two typical wall structures (Concrete block (HCB) and compressed stabilized earth block wall (CSEB)). The yearly cooling transmission loads, according to wall orientations and percentage of radiation blocked were calculated using the explicit finite-difference method under steady periodic conditions. As a result, it was found that the lowest value of optimum insulation thickness (0.09 m) and energy savings (79.80%) were obtained for the south-oriented wall, while the payback period (4.73years) was the highest on the same face compared to all wall orientations. Insulation optimum thickness was higher in the HCB wall (0.0983 m) than in CSEB wall (0.0958 m), however, the payback period was the weakest for the HCB wall compared to the other wall type.

Please cite this article as: E. Wati, P. Meukam, M.K. Nematchoua, Influence of external shading on optimum insulation thickness of building walls in a subtropical region, Applied Thermal Engineering (2015), Abstract 7 This study aims to optimize the thicknesses of insulation layers in external walls of 8 continuously used building in a subtropical region according to shade level. The investigation 9 is carried out under steady periodic conditions for various wall orientations using a Simulink 10 model constructed from H-Tools (the library of Simulink models). Walls are assumed to be 11 insulated using expanded polystyrene material. The shade level of the building site is assumed 12 to be varying from 0 to 97% with an increment of 25% or 22%. Yearly cooling load is 13 calculated and used as input to an economic model for the determination of the optimum 14 insulation thickness. It is seen that as shade level increases, optimum insulation thickness 15 decreases at an average rate of 0.035 cm, 0.029 cm and 0.036 cm per percentage of solar 16 radiation blocked for south, north and east/west oriented wall, respectively. Results also show 17 that energy savings vary between 46.89 $. m ିଶ and 101.29 $. m ିଶ and payback periods vary 18 between 3.56 years and 4.97 years depending on shade level and wall orientation.19