The effort to reduce the consumption generated by the use of buildings is one of the important objectives of today’s global society, involving authorities that regulate the energy performance of buildings, manufacturers of materials, specialists involved in the design and last but not least the occupants of buildings. The habits of the occupants of buildings regarding the indoor comfort temperature have a direct influence on the amount of energy consumed. The paper aims to highlight whether the results expected by applying the values recommended in the regulations are in line with the occupant’s habits. Based on a case study, the energy requirement for heating was assessed using different indoor temperatures, which were established in relation to the temperatures monitored in situ. The inside temperature values were monitored in three buildings, located in the third climatic zone of Romania. The article presents the results of the case study, emphasizing that indoor temperature control and monitoring are of high importance in the desired expectations for energy performance of buildings, to meet the sustainability objectives. Knowing the mutual influence between energy consumption and thermal comfort demands, building designers can find solutions to achieve energy conservation goals.