Considering the magnitude of energy loss in Iran's buildings, development of energy saving and energy optimization methods appears to be essential. To date, many energy saving methods, such as energy auditing, have been developed in this area, though none of them enjoyed high accuracy and efficiency. Optimization methods aided by energy modeling are the most useful tools for energy saving as well as energy loss reduction. In this study, a new model has been developed based on mathematical equations of mass and energy balance between different parts of a building and its surrounding area. Generally, this model integrates two methods of load and heating, ventilation and air conditioning modeling. Furthermore, the presented model allows for simulation of energy-efficient scenarios and their optimization based on life cycle cost analysis method. In this part, capabilities of the model have been closely analyzed based on historical records of existing models. The relations covering boundary conditions at external-internal surfaces; energy equations for building systems; interzone airflow and infiltration; heating, ventilation, and air conditioning models and economic models; and their optimization method and possible solutions have been explained in detail. Complete details about the application of this model for the XYZ case study building will be given in the second part of this article.
