The beginning of this master thesis describes natural gas characteristics, its scope of application, production and processing operations, transport, and distribution to the end-users. It also states the current quantities of world natural gas reserves and the current state of natural gas production in the Republic of Croatia. The second part of the thesis presents the calculation of heat losses and annual consumption of gas for heating, preparation of hot water, and steam for the entire building complex of 130,000 square meters. The second part of the thesis presents the calculation of heat losses and annual consumption of gas for heating as well as the calculation of hot water, and steam preparation for the entire building complex of 130,000 square meters. Based on previous calculations, the design of a gas installation consisting of several sections is performed. Three Viessmann Vitomax 200 LW boilers with a total rated heat output of 14,67 MW were selected for heating and hot water preparation. Two Viessmann Vitomax 200 HS boilers with a total rated heat output of 5,2 MW were selected for steam production. The boilers are located in the boiler room located within the complex. The draft documentation contains the situational plan, floor plan and isometry of the gas installation, air flue system, and detail that shows measuring reduction station.