As a side effect of the need for greater energy efficiency of buildings, there is a problem of decrease of the available interior space affected by the reduction in U-value of parts of thermal building envelope, i.e. an increase in thickness of insulating layer, which is especially present in unheated staircase. Having in mind that present methods of calculation of transmission heat losses through elements of thermal envelope include the adjustment factor which regulates designed temperature conditions if the temperature at the colder side of the element of the thermal envelope differs from that of the external environment, this paper strives to demonstrate that in the case of unheated staircases, this fixed value should be reconsidered and treated as a variable depending on the morphology, i.e. form, size and position of the staircase within the building. This problem has been analyzed on the example of Serbian housing stock and relevant national thermal regulations. Three morphological types of unheated staircases have been distinguished within which three models have been defined and examined with respect to variations in number of floors and percentage of glazing. Average temperatures of staircase volume and temperature correction factors were calculated in following temperature modes: stationary that excluded solar gains and ventilation heat losses and gains, and dynamic with variations in air exchange rates and insolation conditions, expressing in all of the cases variations in calculated values of temperature correction factors in comparison to the prescribed fixed value.