cross-ventilation

This paper investigates the impact of ventilative cooling in residential buildings constructed from light-weight cross-laminated timber. Different temperature-controlled ventilative cooling concepts such as single sided ventilation, cross-ventilation and thermal stack based chimney ventilation concepts are simulated and compared in terms of impact on indoor temperature and robustness to external conditions such as the surroundings and the building orientation.

EN 16798-7:2017 considers that windows on roofs that have a pitch below 60° are not included on the windward side whatever their orientation. It means that roof windows are accounted for, but only on the leeward side when using the existing standard for calculation of air flows, EN 16798-7.

Therefore, in the specific case of a room only equipped with roof windows (e.g. an attic) and aeraulically independent from the rest of the building, whatever the orientation of the roof windows, only the simplified “singlesided” calculation method of EN 16798-7:2017 is applicable.

Cross-ventilation flows (CV) are characterized by significant inflow momentum conservation as fluid flows across an enclosed rectangular volume as a confined jet. When the inflow area is smaller than the volume cross-sectional area the CV flow has distinct jet and recirculation flow regions. The simplified model presented in this paper characterizes the CV flow as the result of a confined axisymmetric jet driving one or two recirculation regions, each of which is a lid-driven cavity flow.

In recent years, with actualization of a global warming issue, the need for simultaneous pursuit of progress of comfort in living space at residential house and energy saving is now becoming greater and greater. In this study, we investigated the indoor thermal environment and air distribution by natural ventilation at earth sweet home in summer, middle and winter seasons in Japan. This house is designed so that the effect of natural ventilation may become high. We report the results with focus on the effects of indoor thermal and air environment by opening window in middle season.

In many parts of Asia as typified by Japan, conditioning of the indoor thermal and air environments using natural ventilation since ancient times. When indoor thermal and air environments are predicted, the use of simulation technologies such as CFD and Heating and Ventilation Network Model has increased. Those have advantages and disadvantages. In addition, AI programs like Neural Network (NN) and Genetic Algorithm (GA) are increasingly utilized in other research areas. In architectural equipment field, there are examples of airconditioning system models with NN.

In predicting flow rate of a building ventilated by wind, the orifice equation is usually used. This conventional method cannot work for the building provided with large openings. Therefore, the final goal of this study is to establish a new prediction method of the cross-ventilation rate, which is based on energy balance inside the stream tubes passing through/around a building. In determining stream tubes, it is beneficial to use CFD. In this study, the accuracy of CFD analysis is studied. Three turbulence models are used in the simulation; i.e.

When it comes to natural ventilation performance for large space cooling during summer time or intermediate seasons, double skin facade(DSF) integrated with cross ventilation(CV) exhibits more energy efficiency than single-side ventilated DSF. In this case, ventilation performance is remarkably affected by climatic conditions. Therefore, it is important to analyze micro climatic conditions before applying this passive technique.

The effects of roof window on ventilation flow rates and reduction of cooling loads in densely populated areas were investigated by using building simulations. In May of the intermediate season, when utilizing roof window, the cumulative number of air exchanges increased by 9 % to 12 % compared to that when the windows at side walls remained open only during the daytime. When the building coverage ratio increased from 0 % to 20 %, the cumulative number of air exchanges decreased and the cumulative cooling loads increased.

Cross-ventilation is regarded to be beneficial control method to obtain thermal comfort in a hot summer without using mechanical devices. Since it is complicated flow phenomenon, details of flow characteristics have not been sufficiently known. The final goal of this work is to establish a new prediction method of flow rate based on energy balance within the stream tube passing through or around the building. To validate numerical results obtained by CFD, they need to be compared with experimental results.

The prediction of indoor airflow is indispensable in evaluating the thermal sensation of occupants in a cross-ventilated space because enhanced heat loss due to the elevated convective heat transfer in the occupied zone is an essential part of improving thermal comfort. A domain decomposition technique was developed to separate CFD for internal cross-ventilation flow from external flow outside buildings, and to predict indoor airflow with reasonable computational effort and sufficient accuracy.