## 2 Current State of Knowledge
To model an existing building, tools are needed to measure the actual thermal properties of building elements and to update their relevant entries in gbXML [38]. Developed by the United States Sustainable Building Council (USGBC), LEED is one of the most recognized built environment assessment programs in the world. LEED has become a reference for some other countries to develop their own sustainability building assessment standards [39]. There are LEED programs in more than 150 countries and territories, representing all continents, except Antarctica. The United States sustainable building council has published a list of the top 10 LEED countries outside the United States, based on the cumulative total LEED certified square meters (GSM) of each country [40]. China is the second largest LEED user outside the United States, with 22.97 million GSM LEED spaces. Since 1998, LEED has been evolving to more accurately represent and integrate emerging sustainable building technologies [41]. The weights in LEED are listed in Table 1. In the grading, the satisfaction degree in each indicator table corresponding to the building is scored. The scores were summarized to obtain the scores of each index. According to the total score of the buildings evaluated, the LEED 4 th edition has four certification grades, namely: certification grades 40-49, silver grades 50-59, gold grades 60-80, and platinum grades above 80 [41]. BREAAM is the world's first comprehensive assessment system for sustainable buildings, and it was introduced to the public in 1990 [42]. It is sponsored and operated by the building research establishment (BRE) in the UK for sustainable building design, and has become one of the most comprehensive and widely recognized measures of built environment performance. BREAAM is widely used in Europe and many other parts of the world. BREAAM's domestic version was replaced by the Code for Sustainable Homes (CSH) in April 2008 [39]. The system, which is mostly used for new and renovated small homes and apartments, aims to ensure that the homes meet people's needs for a high quality of life, while providing a safe and healthy internal environment. According to the characteristics of residential buildings, it has formulated specific contents and relevant weights. Based on a scientific understanding of the relationships among people, buildings, and the environment, the system is evaluated in 10 categories: energy, management, health and comfort, transportation, water, materials, garbage, land use and ecology, pollution, and innovation, as shown in Table 2 [40]. CSH has been fully implemented as a national standard in the UK since May 2010, with the goal of reducing carbon emissions while achieving the environmental sustainability of buildings [35]. The recommendations and applications of CSH could point to the direction \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**S. No 1** & **New Buildings** & **Weight** \\ \hline
1 & Integrated design & 1 \\ \hline
2 & Site selection and transportation & 16 \\ \hline
3 & Sustainable site & 10 \\ \hline
4 & Water-use efficiency (WUE) & 11 \\ \hline
5 & Energy and atmosphere & 33 \\ \hline
6 & Materials and resources & 13 \\ \hline
7 & Indoor environmental quality & 16 \\ \hline
8 & Innovation (bonus points) & 6 \\ \hline
9 & Localization of materials (bonus points) & 4 \\ \hline
10 & Total & 110 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Weights in LEED.