One of the components of the thermal balance of buildings in the warm season is the heat gain from people. In public buildings, heat transfers from people are usually accepted equally to the number of employees and visitors specified in the design documentation. This work aims to consider the non-simultaneous stay of some employees in the workplace during the calculation period of the year with the introduction of an appropriate coefficient for determining the loads of the cold supply of the projected facility. The object of research is an office building. The subject of the study is to consider the heat supply from people when calculating the capacity of the cooling system. Method. Within the framework of this study, two approaches are considered: probabilistic and statistical, which allow us to estimate the probability and relative frequency of the number of employees simultaneously working in the building at the estimated time of the year. When calculating the capacity of the cooling system, the warmest month of the year is selected as the design conditions. The approach proposed by the authors makes it possible to more correctly reduce the unreasonable load reserve and thereby reduce the cost of installation and operation of the building's cooling system in the matter of accounting for heat from people. Results. In the absence of actual information about the use of vacations by employees of the projected facility in the warmest month of the year, a probabilistic approach should be used to determine the coefficient, if such information is available, a statistical one. The article presents the derivation of a formula for the correct calculation of heat input from people, considering not only the intensity of their activities, but also additional factors related to gender and age differences in people and the non-simultaneity of their presence in buildings during the calculated period of the year.