School bus is an important micro-environment for children's health because the level of in-cabin air pollution can increase due to its own exhaust in addition to on-road traffic emissions. However, ...it has been challenging to understand the in-cabin air quality that is associated with complex airflow patterns inside and outside a school bus. This study conducted Computational Fluid Dynamics (CFD) modeling analyses to determine the effects of window openings on the self-pollution for a school bus. Infiltration through the window gaps is modeled by applying variable numbers of active computational cells as a function of the effective area ratio of the opening. The experimental data on ventilation rates from the literature was used to validate the model. Ultrafine particles (UFPs) and black carbon (BC) concentrations were monitored in “real world” field campaigns using school buses. This modeling study examined the airflow pattern inside the school bus under four different types of side-window openings at 20, 40, and 60 mph (i.e., a total of 12 cases). We found that opening the driver's window could allow the infiltration of exhaust through window/door gaps in the back of school bus; whereas, opening windows in the middle of the school bus could mitigate this phenomenon. We also found that an increased driving speed (from 20 mph to 60 mph) could result in a higher ventilation rate (up to 3.4 times) and lower mean age of air (down to 0.29 time) inside the bus.
•Proposed a method to simulate the infiltration airflow through window gaps.•Analyzed the effect of different side-window openings on the airflow pattern.•Measured BC and UFPs concentration inside with different window openings.
In consideration of the sun's path in architectural design, the window systems can be regarded as heat traps, to introduce solar radiation into the buildings in winter. On the contrary, the solar ...radiation passing through the glazing into rooms significantly increases the cooling energy requirements in summer. Due to the optimum solar heat gain magnitudes varying by season in the buildings, a tradeoff solution needs to be explored between the solar radiation interception in summer and the solar heat gain in winter. Here, we separated out the beneficial and the harmful solar radiations from the radiation sky dome model, based on the air temperature data. Then, a new customized radiation sky dome model was created, according to the difference value between the beneficial and harmful solar radiations over a year. Furthermore, the neighboring buildings with various volume and number combinations were assigned to surround the study building, to explore the shading performance on the study building cast by the surrounding building(s). In this work, the average energy saving rate for six chosen study buildings is about 14%, based on the passive strategy of the customized radiation sky dome model.
•HSR and HSR were separated from the solar radiation sky dome model.•A new customized radiation sky dome model was created, based on the DVBHSR.•Energy efficiency building design was based on surrounding building context.•New methods of optimizing shading system and building orientation were proposed.•New approach of optimizing window position was proposed to obtain more BSR.
Abstract In designing eco-buildings, windows play a big part in minimizing the energy load. There has not been any easy-to-use software to speed up the process, even after many recent studies about ...environment-friendly window size, shading, position, and material. Thus, a single-family house with simple geometry in Kvemelto karti, Georgia, was simulated to introduce an alternative method to manage this gap. A building information model (BIM) was devised for this procedure through Autodesk Revit® due to its simplicity, popularity, interoperability and convenience among its users. Not to mention, the energy analysis tool (The Autodesk Insight 360) in Revit (BEM) displays the total energy load while, in this case, focusing on window size, position, material, and shading executed by Autodesk Green Building Studio®. The early energy analysis (the optimum window-to-wall ratio (WWR), the windows’ location in the wall, material, and shading) suggested by BEM does not give enough information to apply in the early stages of design and create a net-zero-energy building. The aim is to show the gap between data-driven from BEM and design strategies and to display the information required to be more detailed. For this purpose, after using Insight 360 (a web-based tool) for investigating window shades, material, and WWR, it has been concluded that there is a need for a more convenient way to automate the process in more depth. They could help to pick a viable widow shading, size, position, and material. Besides, choosing determined factors using just BEM is not practical because detailed characteristics of window factors as determining elements are not defined. This tool has its limitations.
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The energy consumption in buildings contributes substantially to the worldwide energy use and greenhouse gas emissions. One of the crucial elements defining energy consumption is the ...building envelope, which in modern designs includes growing share of fenestration. Due to recent improvements of windows and walls, the thermal bridging effects occurring on their connections, become more significant. Window-to-wall connections appear to be especially important and can contribute up to 40% of the total heat loss caused by thermal bridges in building envelope. Thus, this study is investigating thermal properties of window-to-wall connections. The main scope of the work is to determine the most efficient window position in the window opening regarding minimizing thermal bridging effects. Five different wall constructions are investigated along with two windows with different U-values. The thermal simulation results show that the window position has a crucial impact on the amount of energy loss through the thermal bridges. For each wall type, the most energy-efficient position is found, resulting from detailed analysis of sill, head, and jambs construction details. For some cases placing the window in the most energy-efficient position reduces linear thermal transmittance (LTT) over 50%. Among considered positions, the temperatures on the internal surface of the assemblies are weakly influenced by the window position. Example calculations show that significant share of energy losses from the fenestration presence is caused by thermal bridge occurring on window-to-wall.
Nowadays, the use of renewable energies has increased due to the energy crisis and subsequent environmental issues. The window design significantly affects energy consumption and natural light ...absorption regarding preventing visual discomfort and improving indoor quality with effective external features. Hence, it should be carefully selected from the early stages of design. Thus, the present study investigated the optimal design of windows considering four components of the window-to-wall ratio (WWR), window shape, and positioning on each façade by separately considering the sill height of the window for a general office. The objective was to provide visual comfort and save energy. Applying constraints to the data set can yield an optimization method concerning the variables and their relationship as well as optimal solutions based on the stated goals. Therefore, the desired groups can be accepted as optimal solutions for improving the efficiency of the building. According to the results, the WWR of 30% with the square and horizontal shapes in the upper and central positions were optimal solutions for each window orientation, which had better performance in the north-facing WWR of 40%. Furthermore, several best design solutions were presented in each orientation in terms of energy consumption, daylighting, and visual comfort in the indoor environment. This method also allows the designer to visualize all the data while finding the clients’ desired option by improving the energy efficiency between the variables and choosing the appropriate solution.
Increasing evidence has demonstrated toxic effects of vehicular emitted ultrafine particles (UFPs, diameter < 100 nm), with the highest human exposure usually occurring on and near roadways. Children ...are particularly at risk due to immature respiratory systems and faster breathing rates. In this study, children’s exposure to in-cabin air pollutants, especially UFPs, was measured inside four diesel-powered school buses. Two 1990 and two 2006 model year diesel-powered school buses were selected to represent the age extremes of school buses in service. Each bus was driven on two routine bus runs to study school children’s exposure under different transportation conditions in South Texas. The number concentration and size distribution of UFPs, total particle number concentration, PM
2.5, PM
10, black carbon (BC), CO, and CO
2 levels were monitored inside the buses. The average total particle number concentrations observed inside the school buses ranged from 7.3 × 10
3 to 3.4 × 10
4 particles cm
−3, depending on engine age and window position. When the windows were closed, the in-cabin air pollutants were more likely due to the school buses’ self-pollution. The 1990 model year school buses demonstrated much higher air pollutant concentrations than the 2006 model year ones. When the windows were open, the majority of in-cabin air pollutants came from the outside roadway environment with similar pollutant levels observed regardless of engine ages. The highest average UFP concentration was observed at a bus transfer station where approximately 27 idling school buses were queued to load or unload students. Starting-up and idling generated higher air pollutant levels than the driving state. Higher in-cabin air pollutant concentrations were observed when more students were on board.
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