2. Literature Review
In many countries, the energy consumption benchmarks in office buildings have been studied such as Energy Consumption Guide 19 (ECON19) of United Kingdom [1], on-line benchmark tool of Hong Kong [2], and e-Energy Singapore [3]. All of the benchmarks are based on statistical analysis of survey data and are included all energy consumptions in building. However, calculation methods of normalize energy consumption in terms of kWh/ year of database are various. Nevertheless, the details of each method will not mention in this paper. The summary of those three benchmarks is shown in Table 1.