Retrofit optimization of building systems for future climates using an urban physics model.

To guide building system retrofits for reducing building's operational carbon footprint, a micro-genetic optimization algorithm has been applied. The algorithm is integrated into the Vertical City Weather Generator (VCWG) urban physics model. The model is applied to low-rise residential houses of Toronto, a cold Canadian city, for annual estimations and reductions of electricity/gas consumption and retrofit cost from 2020 to 2100, every decade, under two Representative Concentration Pathway (RCP) climate change scenarios. The building system configuration utilizes a solar thermal collector, photovoltaic collector, wind turbine, building thermal energy storage, and heat pump. Fifteen building variables have been optimized. Compared to a base building, the proposed retrofitted system reduces the electricity consumption by up to 61.71 [%] and the gas consumption by up to 82.67 [%]. The annualized retrofit cost for a 20-year time horizon is about 10-15 thousand Dollars. Some optimized variables are sensitive to the climate change scenario over a long time horizon until 2100, which relate to the thermal energy storage system, phase change material, solar thermal collectors (and the associated working fluid flow rates), solar heat gain coefficient, and roof albedo. Other variables, relating to the ventilation/infiltration rates, building envelop thermal resistance, glazing ratio, wind turbine size, and photovoltaic collectors, do not show such sensitivity. The optimization process is computationally fast, and the solution obtained provides evidence for successful building system retrofits toward energy and cost savings for the climate of Toronto. • A micro-genetic optimization algorithm is applied for building energy and retrofit cost savings. • Fifteen building variables are optimized for a residential house in Toronto for 2020–2100. • The configured system saves up to 61.71% in electricity and 82.67% in gas consumption. • The retrofit cost is estimated as 10–15 thousand Dollars annually for a 20-year horizon. • The optimization algorithm and proposed system show evidence for real energy and cost savings. [ABSTRACT FROM AUTHOR]