Evaluation of Indoor Thermal Comfort on Office Building in Ternate City 1 Associate Professor, Department of Architecture, Khairun University, Ternate-Indonesia. E-mail: mustamin_rahim@yahoo.co.id 2 Professor, Department of Architecture, Hasanuddin University, Makassar-Indonesia. Abstract. This study aims to evaluate the thermal comfort in office building by analyzing temperature, humidity, and wind speed conditions in the room. Research method is performed with the measurement of thermal condition using LSI-LASTEM Multi Logger, HOBO data logger, and HOBO data logger with external sensor. At the time of measurement, thermal condition perceived by employees is observed through the questionnaires of Thermal Sensation Vote (TSV) and Thermal Comfort Vote (TCV). The results show that the thermal condition in office building is uncomfortable level. Natural ventilation system is not effective because of orientation and dimension of ventilations are minimal or not suitable standard, therefore the usage of air conditioning is increased. Key words: Thermal Comfort, Office Building, Natural Ventilation 1. Introduction Climate change occurs in recent years due to increase of CO2 gas emission in the atmosphere. It causes the rising of temperature especially in metropolitan cities. The rise of outdoor temperature has a significant effect on temperature increase inside building, so that it becomes harder to achieve thermal comfort in summer and caused more utilization of Air Conditioner in building. The effect of AC utilization yields to the increase of energy consumption. Buildings account for almost a third of final energy consumption globally and are an equally important source of CO2 emissions in atmosphere [1] . Buildings contribute as much as one third of total global greenhouse gas emissions primarily through the usage of fossil fuels during their operational phase. The building sector contributes up to 30% of global annual green house gas emissions and consumes up to 40% of all energy, both in developed and developing countries [2] . In Ternate City, energy resources is very limited, it only produces by diesel power plant, while demand of energy is continue to increase, primarily because new buildings are constructed. Based on the field observation, cooling system in building is generally using air conditioning. It causes the increasing of energy consumption in building, so that the supply of energy is not enough and power outages are done every day in rotation. This condition can influence to the ventilation system and thermal condition in building especially office building. Therefore, this paper will discussed thermal comfort in office building with condition of natural ventilation system. 2. Research Methodology Research method is performed with the measurement of thermal condition using LSI-LASTEM Multi Logger, HOBO data logger, and HOBO data logger with external sensor. At the time of measurement, thermal condition perceived by employees is observed through the questionnaires of Thermal Sensation Vote (TSV) and Thermal Comfort Vote (TCV). 3. Results And Discussions Thermal comfort is important both for one's well-being and productivity. There are many factors affecting human thermal comfort, such as temperature of surfaces, air temperature, humidity, air movement and personal variables like clothing insulation, activity and metabolism rate. Relative humidity is the percentage of water in air compared to the maximum the air can hold. For ideal comfort relative humidity has to be kept low in hot temperatures. High humidity (60% or above) might become a serious issue in extreme climates as it could cause condensation, destroy or decompose The 4th International Conference on Engineering and Technology Development (ICETD 2017) 75 M Rahim 1 , B Hamzah 2