# Optimized Design of Floor Plan and Components of Prefabricated Building with Energy-Cost Effect
## 1 Introduction  
The issue of global energy consumption is in the spotlight today. The U.S. Information Administration presents a future scenario in which global energy consumption will increase by nearly 50% over the next 30 years or so [1]. Building energy consumption accounts for 21.7% of the national energy consumption in China [2], and there is still work to be done to reduce overall energy consumption in the building industry. Cost limits, of course, are crucial factors in restricting building energy efficiency [3]. The optimization of energy efficiency without the consideration of cost may result in high incremental costs and the inability to promote applications. As a result, energy usage and cost should be considered throughout the optimization process. Many earlier researchers have investigated this topic using the genetic algorithm technique. I2n 2002, [PERSON] et al. used evolutionary algorithms on the DOE2.1E platform to improve the arrangement and size of windows in public buildings to lower the yearly energy consumption [4]. [PERSON] et al. optimized near-zero-energy buildings to achieve a low economic cost [5]. [PERSON] et al. identified the design priorities for cold-climate building facades [6]. However, related research has revealed that diverse optimization targets have conflicting characteristics [7], suggesting that focusing on a single goal is unsuitable in particular optimization schemes. As a result, an increasing number of researchers are attempting to adapt the multi-objective optimum design technique to the purpose of the architecture. With illumination and energy consumption as the optimization targets, [PERSON] et al. employed modeFRONTIER and Daysim to optimize thespacing and angle of the sunshade for the south window of an office [8]. To complete the facade design while guaranteeing building performance, [PERSON] et al. exploited the twin aims of lighting and heating to optimize the curtain wall design parameters (surface angle) of an office building [9]. By using the Grasshopper platform, [PERSON] et al. achieved the performance optimization of a large public building focusing on energy, cost, and daylight [10]. [PERSON] et al. used the Energyplus and JEPlus platforms to create an architectural design plan for a residential project in Shanghai to improve indoor thermal comfort and lower energy consumption [11]. However, the basic models commonly employed in related studies are primarily used for non-assembled buildings--i.e., the optimized solutions often find it difficult to meet the standardization, modularity, and modularization needs of prefabricated buildings. The trend of building industrialization has been evident in recent years. With the deepening of the concept of green and sustainable development, prefabricated buildings are receiving more and more attention from the domestic and international construction community because of their standardization, energy efficiency, and economy [12; 13; 14]. Prefabricated building envelopes can be selected to have an appropriate envelope structure based on the building orientation, climate conditions, and economic costs, among other factors, in order to achieve low energy costs, thanks to their modular design, factory manufacturing, and assembly construction [15]. The application of this approach to the design process, as well as the successful combination of genetic algorithm and assembly construction, is the focus of this study. In summary, the previous studies also had the following shortcomings:  
* Few scholars have applied the synergy of energy consumption and cost to prefabricated buildings. * The models of the former studies can mainly be divided into two categories: one is a generic model with similar characteristics to that obtained from our research (it is usually a city building and is used to propose some common optimization conclusions [4; 8; 9; 10]); the other is generally a specific model, usually for a public building, and the findings primarily relate to the renovation and refurbishment of the building [5; 6; 11].