Indoor air quality in office rooms directly influences occupants' comfort and productivity. Higher air change rates in offices compared to residential buildings increase the heating demand considerably in cold climate countries. Reducing the thermal losses from exterior walls and windows provides the possibility of using low-temperature heating systems in order to reduce the required heating and enhance the occupants' perceived thermal comfort. In the present study, the indoor air quality in an office room under Nordic climate has been investigated using computational fluid dynamics method. A well-insulated window (so-called energy-active window) is installed at the exterior wall. The effect of using two heating emission systems, floor heating, and radiator, on the perceived thermal comfort of the occupants has been studied and compared.