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Genetic Optimization for economic feasibility of refurbishment in buildings

Manzan M., Rossi R., Zandegiacomo De Zorzi E., Lupato G.

CHALLENGE - Energy consumption in the residential sector has been constantly increasing at a global level. Building fabric provides a possible solution since it affects building consumption and allows the adoption of different heating plant systems. This paper investigates the possibility of enhancing the thermal characteristics of a building fabric considering the economic aspect of reducing unnecessary and expensive interventions. The problem consists of the realization of an internal insulation system of a residential apartment. 

SOLUTION - Three refurbishment scenarios have been applied to a relatively recent apartment located in Trieste, Italy with the optimal insulation thickness being the main object of the study. The objectives are lowering the used heating energy consumption and the life cycle refurbishment cost, using a net present value (NPV) approach. A genetic optimization has been implemented in order to search a large number of solutions with multiple objects and constraints. EnergyPlus has been used for dynamic building and plant simulation and modeFRONTIER for the optimization loop setup with the use of MOGA II. The typical support available in Italy for insulation enhancement and window replacement is in the form of tax reduction of 65% of the initial costs. This form of subsidy has a strong effect on NPV since it increases the cash flow for the time in which the reimbursement is active. Three cases are presented. Case 3 considers only a single insulation thickness, such as Case 1, but in addition, the replacement of existing windows with high performance triple glazing systems is considered. For all cases the insulation layers tested increase from 3 cm to 20 cm with steps of 1 cm.

BENEFITS - The paper demonstrates that an automatic optimization approach can help designers identify the best-suited intervention for building refurbishment. By applying a subsidy, the NPV increases reaching positive values assuring the profitability of the investment. These solutions also present lower energy consumption from from an environmental point of view.

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