Historic houses used as museums require stabilized indoor environmental conditions to prevent the degradation of presented objects and the building itself. For preventive conservation, the monitoring of indoor air temperature (T) and relative humidity (RH) values may create a vital database revealing the damaging fluctuations. This study aims to monitor T and RH levels in a historic house used as a museum and propose implementations for stabilizing their preservation condition with minimum energy consumption through architectural interventions. The case study is in İzmir, Türkiye. It is a typical two-storey row house built in 1911. It was registered as a heritage building in 1979 and refunctioned as Radio and Democracy Museum in 2013. In different spaces, old radios with wood, metal, plastic, and wicker material combinations are displayed. Four representative spaces of the museum were monitored for five months to collect the inside T and RH values. The thermal model of the building for current state was generated in DesignBuilder and calibrated for the collected data. Firstly, current energy consumption by HVAC element usage is determined. Then, to provide the required indoor conditions suggested by the ASHRAE Standard, the schedules and set-point of the air-conditioners are rearranged and the energy consumption is derived. Lastly, since the authentic wooden doors separating the indoor spaces into different controllable zones were removed during the refunctioning, thermal modeling was repeated for the authentic separated zone version and the energy consumption rate was compared with previous models. As a result, a management plan was developed.