A detailed study on the building stock of Liege urban area (Belgium) has been conducted during 2011-2012. The study is focused on historic buildings, which were constructed before 1945 and represents a very significant share (68.33%) of Liege building stock. In the Walloon region, the average heating energy consumption per year of the building stock is 408 kWh/m2 and the average heating energy consumption per year stands at 340 kWh/m2 for Liege. Hence, it is important to study existing buildings to improve the energy efficiency as well as thermal comfort standards. It is also important to understand the behaviour of these buildings and the preferred indoor thermal environment of the occupants. Keeping this in mind, the indoor thermal environment has been monitored for ten residential buildings followed by detailed interaction with the occupants to record their preference and expectations about indoor thermal comfort. It was found from the analysis that the fluctuations in the temperature of living room and bedroom with respect to outdoor conditions are a function of occupant’s age, type of heating system and fuel used. It is also found that the average energy expenditure was very high in these buildings. The study further identifies specific areas that need to be taken into consideration in order to improve the thermal comfort and energy efficiency. It put forth the argument that to improve the energy efficiency of occupied houses, occupant’s preference and expectations on thermal comfort needs to be considered for designing sustainable solutions towards improving energy efficiency.