The building automation system is defined as the operation of various building systems (e.g. lighting, air conditioning, firefighting etc.) without the need for human intervention (or minimal human intervention) to control and monitor the internal environment to ensure that it operates at the optimum level. Building automation system provides the internal environment with several features including increased user comfort, reduced operating and maintenance costs, improved control system efficiency and reduced power consumption, as well as increased user productivity. This research studies the effect of the automation system on the performance of engineering firms in Egypt. The problem arises from the absence of periodic evaluation of operating systems, which leads to deterioration of its level. The post-occupancy evaluation (as a tool to measure the success of the design objectives of the building after its construction) is applied to office buildings. The evaluation provides a way to collect data about the building and has a great importance to all participants in the building's life cycle; it includes several measures such as thermal comfort, lighting, acoustics, Sick Building Syndrome (SBS) etc. The objective of the evaluation is to improve the quality of the design, the building and the administration, and thus enhance the building environment. The research used a combined strategy included the descriptive study approach with a comparative analysis of the impact of the automation system using post-occupancy evaluation by conducting 72 questionnaires for two office buildings users, the questionnaire aspects included: indoor environmental quality, Productivity in work and architectural design. The research concluded that levels of satisfaction in non-automated buildings are moderate, compared with higher levels of satisfaction in the automated buildings. The research also concluded that when using fully automated building, the possibility of personal control at different levels of the building must be considered.