EVALUATION OF THE COMBINED EFFECT OF VEGETATION AND NATURAL VENTILATION IN NEARLY ZERO ENERGY MULTI-STOREY BUILDINGS – nZE(ms)B

Cooling load is the main cause of high energy consumption for tall buildings in tropical climates while the construction of tall buildings is an unavoidable practice due to land scarcity in metropolitan cities. In this regard, the use of natural ventilation (NV) in tall buildings can help reducing the energy consumption. However, this solution can also bring the problem of polluted air that may enter the space to be ventilated. If the air is passed through a system that can absorb pollutants and add more oxygen to the air, the problem may almost be solved. Building integrated vegetation (BIV) systems can help solving this problem. So, if the air entering buildings passes through dense vegetation, it may not only be cleaned but also cooled due to evapotranspiration effect of plants. Furthermore, the choice and location of vegetation can increase or decrease wind speed. Incorporation of the successful implementation of these green strategies lead to the design of nearly zero energy multi-storey buildings (nZEmsB). A successful implementation of these strategies for an optimized outcome in terms of reduction in cooling load and the performance of NV is evaluated through computational fluid dynamics (CFD) software. A conventional method is to design the building using passive strategies i.e. NV and BIV, and then evaluating the design using a CFD tool to evaluate the efficiency of combined effect of NV and BIV. If the simulation results are not optimal, the design has to be modified and the simulation process has to be repeated. However, this is a time taking approach as the design of a tall building itself is a complex process and any wrong decision regarding spatial planning, overall building configuration and choice of BIV systems may become the reason for the failure of an implementation resorting to this passive technique. The concept of optimization in Architecture, has brought a novel perspective for the designers to achieve the better design solutions in reduced time. There are many optimization models and tools available for the energy efficient design of buildings, however there is almost no research available regarding the optimization tools available for designing tall buildings incorporating a combination of NV and BIV systems. This research provides an optimization model for finding the optimal design choice for tall buildings using NV and SG as a cooling technique in hot and humid climates. The deliverables of this research are a decision support framework for the development of the optimization tool, a generative tool, that is capable of developing 3D models of tall buildings with the geometrical characteristics (found in literature) suitable for the best implementation of NV and SG to reduce the cooling load in hot and humid climate; integration of a CFD simulation tool to the generative tool resorting to RhinoCFD for the evaluation of effectiveness of NV; and an optimization algorithm, based on evolutionary algorithms. This Model is developed using visual programming and scripting on Grasshopper/ Rhino3D. The model does not require users to have in depth knowledge of computational fluid dynamics and still can inform the designer regarding the best design option. It will assist designers to make informed decisions for achieving effective natural ventilation design through building form, orientation, space planning along with allocation of SG at an early stage of design. The results will contribute to the development of energy efficient and energy independent communities.