The building sector has become a major source of worldwide carbon emissions and energy consumption because of rapid population growth and a continuous environmental strain caused by humanity. A lack of consistent data on life-cycle carbon emissions and energy demand at the neighbourhood level has made it difficult to understand the origins of climate change at this scale. A sensitivity analysis brought clarity concerning the extent of environmental impacts on future climate evolution. From this perspective, the authors aimed to evaluate, analyse, compare, and provides recommendations to reduce carbon emissions, as well as the energy required by three types of neighbourhoods (urban, rural, and sustainable) located in and adapted to all countries worldwide. The most important parameters affecting carbon emission and energy consumption were analysed, including the energy mix of countries, local building materials and climate, technological solutions utilised, daily mobility, and occupied spaces. The results indicated that the highest levels of carbon dioxide emissions were produced by countries with prosperous economies, such as China, the United States, India, Germany, and Poland, because of high concentrations of coal in their energy mixes. Modernising cities through the construction of new ecodistricts and increasing the use of new techniques for substantial renovations of outdated buildings worldwide could mitigate the amount of greenhouse gases emitted by neighbourhoods 53-97 % by 2050. Moreover, by combining substantial building renovations with the installation of photovoltaic panels on roofs, the objective of 'zero carbon' at the neighbourhood level could be achievable by 2050 in rural neighbourhoods. Radical changes in the judicious choice of construction materials and use of green energy production represent targeted opportunities to resolve the future climate dilemma.

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

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