Abstract. In the following article the author proposes the solution for a properly functioning natural ventilation system based on the use of supply and exhaust ducts, i.e. by designing a natural balanced ventilation system. The paper is devoted to test results of air flow through natural ventilation supply-exhaust ducts in the rooms located on the lower floor of the building. The simulations conducted in ANSYS Fluent software relate to such issues as: pressure system inside the room and in the exhaust duct, distribution of air temperatures in the room, vector direction of airflow through supplyexhaust ducts and in the analysed room. Three types of solutions were selected for the tests: air inflow into the room through the air intake located at the basement level, air inflow through the window ventilator (although no longer used, this solution can be found in many existing residential buildings) and the natural ventilation system supported with the so-called "solar chimney". All simulations were conducted with an outdoor temperature of +3 degrees C. The indoor temperature is + 20 degrees C, considered to be the minimum thermal comfort level. In the era of common building sealing, the presented ventilation system may be a good solution that guarantees proper functioning of natural ventilation. In all cases presented, it meets the normative regulations and requirements for the ventilation air stream and the air exchange rate in the room. The paper (first part) describes test results concerning the room located on the lower floor of the building, i.e. with a short supply duct and a 12-meter long exhaust duct.
The choice of topicFrequently conducted construction works involving thermal modernization of a building limit the inflow of the appropriate air stream to the living quarters. This is the reason for the emerging problems associated with improperly functioning gravity ventilation that operates periodically and with variable efficiency. In the vast majority of cases, existing residential buildings in Poland are created on the basis of a natural ventilation system. In accordance with the requirements of PN-83/B-03430, new structures of up to 9 storeys can also be equipped with a natural ventilation system. In both cases, the proposed solution can have a broad scope of application in our country. It does not require large financial outlays or the use of complex, expensive ventilation devices. Following the example of many world famous construction projects that have been created on the basis of a selected natural ventilation system, it can bring satisfactory results, primarily related to human health and good technical