## 1 Introduction
However, policies and regulations and a complete system that focuses on the whole life cycle of the ZEB should be implemented. One of the most effective ways toward ZEBs is building retrofitting, which is defined as a set of physical and operational changes that will minimize a building's energy consumption [1]. A retrofitting plan may include addition, deletion, removal, or replacement of one or more of a building's envelope components or electrical equipment. Retrofitting measures may include adding wall insulation, changing electrical equipment to more energy-efficient ones, downsizing the HVAC system according to the cooling load, or investing in renewable energy technologies [9]. For instance, to help achieve net ZEBs for existing buildings, the authors in [10] used the Building Energy Code (BEC) software and Thailand energy code for a building's retrofitting evaluation along with economic analysis. The authors reported an energy consumption reduction of almost 50%, a 4.36-year discounted payback period (DPP), and a 19% internal rate of return (IRR). In another example [11], the authors investigated the effect of additional internal insulation on energy consumption for heating and cooling in a residential building, where the global cost method and simple payback time were used to assess and compare the economic viability of the retrofit systems. The results show that though internal wall insulation can replace traditional external insulation, the simple payback time is unacceptably long. To also help achieve net ZEBs, the authors in [12] developed a building retrofitting assessment and optimization model to minimize a retrofitted building's carbon emissions, economic costs, and energy usage over its life cycle. A three-floor office building was used to show the utility of the approach, which mainly focused on passive options, including improving the envelope's thermal properties and installing renewable energy devices. A different approach to minimizing energy consumption is to minimize emissions. The authors in the paper [13] conducted a life cycle assessment (LCA) that consisted of evaluating both embodied and operational emissions of different retrofitting scenarios. A case study (an office building in Norway) showed that the CO\({}_{2}\)-eq associated with the operational energy use was reduced by around 31-34% while the net total CO\({}_{2}\)-eq could be reduced by up to 52%. In another study [14], the authors built a decision-making model for optimum energy retrofitting strategies in residential buildings and conducted a case study where four retrofitting plans with different savings-to-investment ratio and payback periods were generated. However, selecting the optimal retrofitting plan is challenging because of many constraints, including budget, comfort requirements (heating and cooling loads), economic benefits (return on investment, payback period, savings-to-investment ratio, etc. ), energy savings, and government requirements. In addition, applying an energy efficiency program outside its country of origin proved to be difficult because of the variations in climate, geography, economics, and culture between the countries. For example, the efficacy of the green building rating tools is controversial because it emphasizes the ecological aspect and partly neglects the economic, social, and cultural aspects [15; 16]. Consequently, there is a need to develop a framework that decision makers around the world (mainly residential and commercial building owners) can follow in order to achieve the best results out of a retrofitting plan. The motivations behind building such a framework are as follows:  
* There is no such framework that takes the decision maker through the whole process of developing a retrofitting plan. * Some research papers focus on one type of retrofitting measure and ignore the others, for example, considering the building envelope and ignoring electrical and mechanical equipment [17].