For natural ventilation of rooms there is a wide range of possibilities with regard to the selection of window type, size and location. A bottom hung window mounted near the ceiling is often used as it has proved to work well with regard to draught risk and thermal comfort in the room. However, there is a need for more detailed information on the performance of this and other types of windows to make it possible to use improved design methods for natural ventilation systems.
In dwellings ventilated by extract ventilation there are common complaints of cold draught caused by the supply air entering the room through openings close to the windows. This paper reports on studies of unconventional ways to distribute the supply air in order to minimise the risk of such problems. Experiments have been done where the supply air device is located in the hall of an apartment. The ventilation efficiency in the rooms adjacent to the hall has been studied with open and closed doors. The behaviour of gravity currents has also been studied in scale models.
Air leakage and duct wall conduction in forced air distribution systems often waste 20% to 40% of the energy used to condition residences in hot, humid climates. The simulation of these forced air distribution system leakages, their attendant uncontrolled airflows within the building system, and their consequential energy uses may be achieved by treating building spaces as pressure vessels (nodes) that are interconnected with the forced air distribution system, the outdoors, and each other through the basic laws of pressure and airflow.
Computational Fluid Dynamics (CFD) has been used to predict the indoor environment airflow and overall ventilation effectiveness of natural or mechanical air distribution systems. This paper highlights some applications and criticism work made on CFD in order to establish an understanding of the limitations of CFD in predicting room airflow. It is concluded that though CFD is a powerful tool for simulation, the software complexities, computational power and the level of expertise that CFD codes require shape the greatest challenges to beginners in this field.
A large number of modem European buildings are equipped with ducted air distribution systems. To investigate the implications of duct leakage, a field study was performed on 42 duct systems in Belgium and France. The measurement data confirm the findings of the few earlier experimental investigations on these matters in Europe. In our sample, the leakage rate appears to be typically three times greater than the maximum permitted leakage adopted in EUROVENT 2/2 (Class A).
A case study of the ventilation characteristics of office accommodation forming part of a recently refurbished building is presented. A mechanical system has been installed to ventilate and cool two floors that are interconnected by a series of atria, with a novel application of displacement ventilation applied where there is a very low ceiling height. The air distribution and air quality within the space have been studied by the application of computational fluid dynamics (cFD) to allow the computation of air change effectiveness in terms of local mean age.
A large number of modern European buildings are equipped with ducted air distribution systems. Because they represent a key parameter for achieving a good indoor climate, increased attention has been given to their performance during the past fifty years. One aspect that is particularly developed in this handbook concerns the airtightness of the ductwork, which has been identified as a major source of inadequate functioning and energy wastage of HVAC systems. The investigations were carried out within the framework of the DUCT project (1997-1998).
This study investigates the fresh air distribution in 2 or 3-unit multifamily buildings before and after weatherization and evaluates the effectiveness of exhaust-only ventilation in providing the minimum recommended fresh air flows to dwellings in such buildings. Lowrise multifamily buildings often have no mechanical ventilation system and rely on the air leakage through the exterior envelope to provide outdoor air to occupants.