Window Ventilation Research Articles

Performance analysis of a novel hybrid CdTe-PCM multi-layer ventilated window system for building application: An experimental and numerical study

Thermal energy storage (TES) is regarded a significant approach to develop the solar energy and phase-change energy storage is one of the most commonly adopted methods. In this work, phase change materials (PCMs) was integrated with a CdTe multi-layer PV ventilated window system and two groups of continuous full-day experiments were conducted under different operating modes. Mathematical model of the novel system was established and validated against the experimental data. Based on the verified model, impacts of air cavity's dimension and PCM properties were investigated and annual performance was predicted and compared with another two ventilated windows. Results indicated this novel system could achieve effective multiple functions of power generation, space heating, heat preservation and ventilation cooling. Properly increasing the air cavity's height and thickness was beneficial for the system's passive space heating capacity. Height-to-width ratio of the air cavity was recommended as around 1.5 for optimal space heating capacity. Phase change range of the PCM was recommended at 28 °C–29 °C. Compared with another two systems, this system achieved the optimal electrical and space heating performance. Annual indoor air-conditioning load saving ratios of this novel system compared with another two systems were respectively 6.72 % and 6.08 %.

Computational Fluid Dynamics-Based Calculation of Aerosol Transport in a Classroom with Window Ventilation, Mechanical Ventilation and Mobile Air Purifier

During the SARS-CoV-2 pandemic, the air quality and infection risk in classrooms were the focus of many investigations. Despite general recommendations for sufficient ventilation, quantitative analyses were often lacking due to the large number of combinations of boundary conditions. Hence, in this paper, we describe a computational fluid dynamics model that predicts the time-resolved airflow for a typical 45 min classroom scenario. We model 28 students and a teacher, each emitting CO2 and an individual aerosol. We investigated 13 ventilation setups with window or mechanical ventilation and different positions and operating conditions of an additional air purifier. The ventilation performance is assessed by evaluating the ventilation effectiveness, aerosol removal effectiveness, local air exchange efficiency and overall inhaled aerosol mass of the occupants, which is a measure of the infection risk. If the window is opened according to the “20-5-20” recommendation, the incoming airflow reduces both the CO2 and aerosol concentration whilst decreasing the thermal comfort at low ambient temperatures. An active air purifier enhances aerosol removal, but, depending on the position, the local air exchange efficiency and individual aerosol inhalation vary. If mechanical ventilation with 700 m3/h is utilised, the CO2 concentration is kept below 1250 ppm while also effectively removing aerosol from the classroom.

Annual analysis and comparison of the comprehensive performance of a CdTe PV ventilated window integrated with vacuum glazing in different climate regions

In this paper, a CdTe photovoltaic double-skin ventilated window integrated with vacuum glazing (VPV-DSV) is proposed. The mathematical model of VPV-DSV was developed and validated through tests in Hefei, China. Annual energy performance and the economic analysis of the VPV-DSV was evaluated and compared with the other two PV-DSVs and an insulating glazed window (IG) under climate conditions of five selected cities, including Changchun, Hefei, Kunming, Shenzhen, and Shijiazhuang. Moreover, effects of window design factors, including the window-to-wall ratio, PV coverage, and pillar spacing of the VG, were explored. Results indicated that: (1) the VPV-DSV produced the best energy saving results and the least energy consumption. (2) NECs of the VPV-DSV in the five cities above was 955.05 kW•h, 464.31 kW•h, 110.66 kW•h, 53.71 kW•h, and 443.14 kW•h, respectively. (3) Due to high cost of the VG, the VPV-DSV only had the best economic performance in Shenzhen and the NPV was 3931.47 CNY. (4) The WWR and PV coverage had obvious impacts on the overall performance of the VPV-DSV, while the pillar spacing only had a more significant impact on the air conditioning energy consumption.

Combined wind catchers and side windows for cross ventilation in row houses

Purpose This paper aims to explore the efficiency of natural ventilation in the bedrooms of typical two-storeyed row houses with newly reconfigured design that incorporate rooftop wind catchers and side windows to create cross ventilation. Design/methodology/approach A CFD program was used to assess average air velocity coefficient (Cv) in 32 airflow cases. Parameters include location of openings with respect to wind direction, inlet-to-outlet area ratio (IOR) and opening-to-floor area ratio (OFR). Findings The results reveal that indoor air velocities in the cases of air entering wind catchers are generally higher than those in the cases of air entering side windows while air velocities at the openings are the opposite. The IOR of 1:2 provides best results in terms of both velocities of the indoor air and velocities at the openings. Increasing the OFR from 20% to 50% generally improves indoor air velocities and airflow rates. Originality/value This study proved that the new solution of combining one-sided wind catchers and side windows can effectively solve the problem of ventilation uniquely existing in the conditions of typical row houses by catching prevailing wind from two opposite directions into multiple rooms. The results are given as non-dimensional air velocities, which can be interpreted with any climatic data, and therefore can be applied to row houses in any locations and climatic conditions. The findings can create a new and efficient design of row houses that benefits building industry.

Analysis of Indoor Radon Concentration Levels and Influencing Factors in Kunshan

Radon is a natural radioactive gas widely existing, in order to study the indoor radon level and influencing factors in Kunshan City, the indoor radon concentration of three buildings was analyzed. It was found that all of them met the indoor radon concentration limit specified in the national standard, and the indoor radon concentration was mainly related to soil radon concentration, indoor ventilation and climate. Indoor radon can be controlled from the following points: (1) While building a new building, test the radon concentration in the soil and try to avoid areas with high concentrations. (2) Pay attention to daily window ventilation, especially in cold weather and poor air circulation in winter. (3) Find and prevent indoor radon sources, building materials will also release a certain amount of radon, and interior decoration materials must be selected to meet national standards.

Aerodynamic mechanism of a combined buffer hood for mitigating micro-pressure waves at the 400 km/h high-speed railway tunnel portal

As high-speed trains exceed 400 km/h, tunnel aerodynamics pose significant challenges. The hat oblique tunnel buffer hood with enlarged cross section and ventilation windows (HEW) is a promising solution to mitigate micro-pressure waves (MPWs). However, there is limited research on HEW ventilation window configurations. Thus, field measurements and numerical simulations were conducted using the slip grid technique and an improved delayed eddy simulation turbulence model, with validation against field data. The study investigated the effects of aperture rate and ventilation window arrangement, analyzing the initial compression wave, pressure gradient, MPW, and flow field in the tunnel buffer hood under various ventilation window setups. Findings emphasize that increasing the aperture rate or placing ventilation windows near the tunnel entrance reduces MPWs when a high-speed train enters the buffer hood. However, it intensifies MPWs when the train transitions from the buffer hood to the tunnel. Optimal MPW mitigation is achieved with approximately 15% aperture rate and a ventilation window distance from the slope end of 0.3–0.4 times the enlarged cross section length. Double ventilation windows outperform single or three windows in MPW reduction, with longitudinally arranged windows at the top facilitating more efficient high-pressure air escape compared to circumferential windows.

Optimizing window ventilation strategies for high-rise residential buildings with U-shaped lightwell: Simulating gaseous pollutant cross-room transmission

The lightwell structure widely used in high-rise residential buildings becomes a pathway for the cross-room transmission of gaseous pollutants. In order to devise effective strategies for window ventilation, it is necessary to conduct research on the transmission characteristics of pollutants in the lightwell. The unsteady-state characteristic of the temperature in natural conditions is represented using a sine function. The transmission of pollutants in the lightwell during the 24 h was simulated by computational fluid dynamics (CFD) employing the RNG k-ε turbulence model and continuous phase model. Three pollution sources were considered at three typical building heights: low floor (5 floors), middle floor (18 floors), and high floor (32 floors). Moreover, the window ventilation time was accurately determined by calculating the room's re-entry ratio near the pollution sources. The results show that the day (24 h) can be divided into three time periods based on the airflow pattern in the lightwell: the downward airflow time (17:00 to 2:30), the upward airflow time (5:00 to 15:00), and the transition time (2:30 to 5:00 and 15:00 to 17:00). During the transition time, pollutant is transmitted both horizontally and vertically, and all rooms around the pollution source are unsuitable for window ventilation.

Investigation of the effectiveness of top-down natural ventilation of a poultry building in a hot-summer mediterranean climate

In this study, computational fluid dynamics (CFD) was used to examine the efficiency of ventilation and airflow patterns in a multi-level layer hen house. The utilization of windcatchers as a natural ventilation system was the main area of focus. By comparing CFD simulations with experimental data using ANSYS Fluent, the results were validated. The findings showed good agreement in airflow velocity within the windcatchers and throughout the entire building between the CFD calculations and the experimental tests, resulting in uniform airflow distribution and the absence of turbulence in the area where the chickens were kept. This setup provided the layer hens with an acceptable level of comfort by maintaining a consistent and steady temperature profile. The windcatcher-based model demonstrated better temperature uniformity than mechanical window ventilation. The study also emphasized the importance of maintaining appropriate humidity levels throughout the building to ensure the comfort and productivity of layer hens. The advantages of the windcatcher-based system in terms of temperature distribution and airflow control were highlighted by comparison with an alternative ventilation model. These results underscore the importance of using natural ventilation systems, such as windcatchers, to create optimal ventilation conditions and provide layer hens with a comfortable and productive environment (resulting in a temperature reduction from 29°C to 19.85°C with a low and uniform air velocity ranging from 0 m/s to 0.7 m/s at cage level). Practical application An effective and eco-friendly approach to enhance animal health and productivity in poultry farms is to install a natural ventilation system with wind collectors. This setup creates optimal conditions for the animals by improving air quality, regulating temperature, and fine-tuning ventilation. Additionally, it promotes overall sustainability in poultry facilities by lowering energy costs and advocating for environmentally friendly management, aligning agricultural practices with stringent environmental standards.

Assessing the performance of the airflow window for ventilation and thermal comfort in office rooms

Assessing the performance of the airflow window for ventilation and thermal comfort in office rooms

Associations between home environmental factors and childhood eczema and related symptoms in different cities in China

Previous studies have shown significant associations between home environmental factors and childhood eczema. However, few studies have compared how associations differ in different regions. This study investigated associations between home environmental factors and childhood eczema ever, and related symptoms including itchy rash (IR) and being awakened by itchy rash at night (awake by IR) in 4 cities located in different regions of China, based on cross-sectional investigations during 2010–2012. We used two-step analysis to explore the associations between influencing factors and eczema/related symptoms: first, group Least Absolute Shrinkage and Selection Operator (LASSO) was conducted to identify important factors among a list of candidates; then, the associations in total study population and in each city were estimated using logistic regression. We found these home environmental factors to be risk factors for eczema or related symptoms: large residence size, shared room, air cleaner at home, abnormal smell, perceived dry air, visible mold or damp stains, cooking with coal or wood, painted wall, incense, mice, new furniture during pregnancy, abnormal smell at birth, window condensation at birth and environmental tobacco smoke at birth. Environmental protective factors were rural house location and window ventilation. Associations of factors with eczema/related symptoms differed across cities. For example, air conditioning was protective for eczema in Beijing and awakening by IR in Shanghai with ORs of 0.70 (95%CI: 0.52, 0.95) and 0.33 (95%CI: 0.14, 0.81) respectively, but not significant in other cities. Our results have implications for improving home environments to reduce the risk of childhood eczema/related symptoms in different regions of China.

Hybrid ventilation in residential and office buildings

This project is focused on hybrid ventilation systems, a combination of natural and mechanical ventilation in residential and office buildings. Especially in dwellings hybrid ventilation systems are quite common. For instance, this can be the frequently occurring combination of exhaust fans in bathroom and toilet and / or a range hood in the kitchen with window ventilation in the other rooms. Currently, these systems are part of the planning reality, however, there are neither planning aids nor focused building standards available. A recently completed research project documents the state of the scientific knowledge, identifies most common planning challenges, and thus provides the basis for future planning aids for hybrid ventilation. This paper sets out to define the term “hybrid ventilation”, presents the most common hybrid ventilation systems in Switzerland and gives planning guidelines for current components of hybrid ventilation systems.

Characterizing indoor air quality, thermal environment and window opening in natural-ventilated Norwegian bedrooms: An extensive field study

To generalize research on indoor air quality (IAQ) in bedrooms, the objective of this article is to characterize IAQ for the cold climate of Norway. The relationship between ventilation, indoor thermal environment and IAQ is revealed. 58 natural-ventilated bedrooms with different levels of renovation were investigated using detailed measurements during the heating season. Compared to other studies in Nordic climate, a larger fraction of the occupants used extensive window openings. A larger fraction of the bedrooms showed low CO2 concentrations. Only few other studies also measured TVOC concentrations. Its average value was well correlated with CO2. However, TVOC concentration is characterized by more peaks. Low CO2 concentrations were found with extensive window openings. Nonetheless, extensive window openings did not systematically lead to low CO2 concentrations, for instance the influence of curtains is shown. It is confirmed that the door opening can lead to relatively low CO2 concentrations when the window is closed. The highest CO2 concentrations are found with the window and door closed. The study confirms relatively low temperatures in bedrooms. Nevertheless, no clear correlation between the indoor temperature and the fraction of time with the window opened was observed. For instance, the lowest bedroom temperatures were obtained using window opening, but also with the window closed. Finally, the results suggest that it is possible to achieve a high IAQ with window ventilation when this is a deliberate strategy (if no filtering of the fresh air is needed), also in renovated buildings where the envelope airtightness has been improved.

Incorporating users’ adaptive behaviors into multi-objective optimization of shading devices: A case study of an office room in Qingdao

Users' adaptive behaviors significantly affect the indoor environment and energy use. Neglecting them would introduce considerable uncertainty in the computer simulation results and lead to suboptimal or even invalid energy-efficiency solutions in optimization. To address this issue, we abstracted and simplified three user behavior patterns, including adjustment of operable shading devices, switching on/off artificial lighting, and opening windows for natural ventilation by a brief literature review. We then developed a new simulation approach that incorporates these behavior patterns and applied it to optimize the exterior fixed solar shade design of a south-facing office room in Qingdao as an example. The baseline model was established and validated in both daylight and energy simulations. The results demonstrate that the addition of user behavior models has a significant impact on both illuminance and load simulation results. The evaluation of each shading solution under the traditional approach and the newly-developed approach shows considerable differences, leading to the selection of different optimal solutions. Ultimately, the 0.6-meter-long type 8 (horizontal sunshade combined with vertical triangular panels on both sides) and 0.7-meter-long type 4 (double-sided vertical shading) were selected as the optimal solution using the traditional approach and new approach, respectively. This research offers valuable insights into the user behavior pattern and uses a shading optimization example to demonstrate the significant impact of incorporating adaptive behavior mechanisms on simulation and optimization results. The approach established in this paper has the potential to be extended to other solutions, being conducive to the study of refined building efficiency strategies for different conditions.

A seasonal experimental study on a novel CdTe based multi-layer PV ventilated window system integrated with PCM under different operating modes

To expand the functions of building window and enhance its thermal performance, a novel CdTe multi-layer PV ventilated window system integrated with phase change material (PCM) was proposed. The novel window system was fabricated, constructed and installed on the south façade of a building room and several groups of seasonal experiments were conducted under different operating modes. Electrical, thermal and daylighting performance of the system were investigated. Main conclusions are: (1) For the heating season mode experiment, daily total electricity generation (EPV) and average electrical efficiency (ηe) were 0.383 kWh and 7.39 %. Room air temperature difference (ΔTroom) between the experimental room and reference room was in the range of 0.88 °C–7.04 °C. Effective functions of space heating and heat preservations were achieved; (2) For the cooling season mode, daily EPV and average ηe were 0.159 kWh and 6.33 %. ΔTroom was in the range of −4.26 °C to −1.26 °C. Effective functions of passive ventilation cooling was realized; (3) The novel window system can provide useful daylight illuminance (UDI) for most time during the working time; (4) Based on the experiment results on transition season, other alternative operating strategies were recommended for specific different ambient condition days.

Optimum window-opening control for naturally ventilated buildings with phase change materials in the hot and humid climate of Indonesia

This study aims to determine the optimum window-opening control that maximizes annual thermal comfort using ventilative cooling, i.e., night and comfort ventilation, in naturally ventilated buildings where phase change materials (PCMs) are used. A thermal energy simulation (TES) coupled with an airflow network model was constructed to evaluate the comfort ventilation and thermal storage effects of the PCMs by controlling the window-opening patterns. The EnergyPlus-based coupled TES model was validated by comparing with the field measurement results of a full-scale experimental building in Indonesia. The root-mean-square errors of the temperature and air speeds at the center of the target building ranged from 0.2 to 0.5 °C and 0.1–0.2 m/s, respectively. The accuracy of the coupled TES was similar to that of computational fluid dynamics coupled with the heat balance analysis, which can simulate the spatial distributions of temperature and air speeds. The annual simulation results showed that prioritizing the thermal storage effect of the PCMs in the morning and comfort ventilation in the afternoon increases the thermal comfort period. For the optimum window-opening control to maximize thermal comfort in the hot and humid climate, an indoor temperature of 27 °C can be considered a criterion to open the windows for comfort ventilation in addition to night ventilation for the thermal storage effect. When this criterion was applied, the thermal comfort period in the room with PCMs increased to 83.3 %. Accordingly, the reduction in electricity consumption for space cooling was 41 % less than that in a control room without PCMs.

Design Of aesthetic acoustic metamaterials window panel based on Sierpiński triangle for sound-silencing with free airflow

Design of high-efficiency, low frequency (<1000Hz) soundproof window or wall absorber which is transparent to airflow is presented. Due to the massive rise in human population and modernization, environmental noise has significantly risen globally. Prolonged noise exposure can cause severe physiological and psychological symptoms like nausea, headaches, fatigue, and insomnia. There has been continuous growth in building construction and infrastructure like offices, bus stops, and airports due to urban population. Generally, a ventilated window is used for getting fresh air into the room, but at the same time, unwanted noise comes along. Researchers used traditional approaches like noise barrier mats in front of the window or designed the entire window using sound-absorbing materials. However, this solution is not aesthetically pleasing, and at the same time, it is heavy and not adequate for low-frequency noise shielding. To address this challenge, we design a transparent hexagonal panel based on Sierpiński fractal triangle which is aesthetically pleasing, demonstrates normal incident sound absorption coefficient more than 0.96 around 700 Hz and transmission loss around 23 dB, while maintaining air circulation through triangular cutout. Next, we present a concept of fabrication of large acoustic panel for large-scale applications which lead to suppressing the urban noise pollution

Indoor Climate Monitoring in Office Buildings—Comparative Analysis of Two Office Buildings without Air Conditioning

Against the background of climate protection and the rising costs of a fossil-fuel-based energy supply, the interest in the energy performance and indoor climate of buildings in real operation is rising. This paper, therefore, deals with the indoor climate investigation of two medium-sized office buildings in Germany by taking measurements over a whole year. These relate to one new building and one refurbished building. Sensors of various types were installed and operated in a large number of office rooms, so that in total results are available for over 100 rooms, typically occupied by one or two persons. The analysis focuses on the indoor temperature in summer and the air quality in winter based on the CO2 concentration. The comfort classes according to DIN EN 16798 including the adaptive comfort approach are used as a basis to cluster the results. Both buildings have movable sun protection and openable windows but no facilities for active cooling. They, thus, represent a large number of existing ‘low tech’ office buildings in Germany and central Europe. The results reflect the respective building concepts but also show a wide range between the rooms due to the user preferences and behaviour. The refurbished building shows better results, especially in terms of air quality but also in terms of summer room temperatures. This underlines the benefit of the targeted measures as a result of an analysis of the deficits in the existing building before the refurbishment. The additional measures for decentralised mechanical ventilation and passive cooling are having positive effects. As part of the projects, further measures to improve the indoor climate were investigated in both buildings. In one case, this involved CO2 traffic lights to stimulate personal window ventilation in winter, and in the other, the use of newly developed individual ceiling fans supports convective heat dissipation on the human body during hot spells in summer. The positive effect could be demonstrated for both measures.

Determinants of manual window control for natural ventilation in homes

Understanding energy-related occupant behavior can improve the energy efficiency of homes. Natural ventilation is one of the energy-related complex occupant behavior which influences both the thermal environment and indoor pollutants levels. The objective of the present study is to find determinant parameters of occupant behavior related to the manual control of windows for natural ventilation in homes. The field monitoring was carried out in thirteen sample homes from December 7, 2017, to December 31, 2022. The importance of twenty outdoor and indoor physical parameters was calculated by the Random Forest algorithm from the data set of the sample homes. The importance of the parameters changed from sample home to sample home and from season to season. And there was also a clear difference between the driving parameters for opening and closing windows in the sample homes. The Random Forest algorithm predicted both window opening and closing behavior with high accuracy when the outdoor and indoor seven parameters were applied. The results of the present study could be applied to develop occupant behavior models that can be implemented in energy simulation tools.

Dynamic modeling and data fitting of climatic and environmental factors and people's behavior factors on hand, foot, and mouth disease (HFMD) in Shanghai, China

BackgroundHand, foot, and mouth disease (HFMD) appear to be a multi-wave outbreak with unknown mechanisms. We investigate the effects of climatic and environmental factors and changes in people's behavior factors that may be caused by external factors: temperature, relative humidity, and school opening and closing. MethodsDistributed lag nonlinear model (DLNM) and dynamic model are used to research multi-wave outbreaks of HFMD. Climatic and environmental factors impact on transmission rate β(t) is modeled through DLNM and then substituted into this relationship to establish the dynamic model with reported case data to test for validity. ResultsRelative risk (RR) of HFMD infection increases with increasing temperature. The RR of infection first increases and then decreases with the increase of relative humidity. For the model fitting HFMD dynamic, time average basic reproduction number [R0] of Stage I (without vaccine) and Stage II (with EV71 vaccine) are 1.9362 and 1.5478, respectively. Temperature has the highest explanatory power, followed by school opening and closing, and relative humidity. ConclusionWe obtain three conclusions about the prevention and control of HFMD. 1) According to the temperature, relative humidity and school start time, the outbreak peak of HFMD should be warned and targeted prevention and control measures should be taken. 2) Reduce high indoor temperature when more than 31.5 oC, and increase low relative humidity when less than 77.5% by opening the window for ventilation, adding houseplants, using air conditioners and humidifiers, reducing the incidence of HFMD and the number of infections. 3) The risk of HFMD transmission during winter vacations is higher than during summer vacations. It is necessary to strengthen the publicity of HFMD prevention knowledge before winter vacations and strengthen the disinfection control measures during winter vacations in children's hospitals, school classrooms, and other places where children gather to reduce the frequency of staff turnover during winter vacations.

Impact of outdoor particulate matter 2.5 pollution on natural ventilation energy saving potential in office buildings in China

Natural ventilation improves building energy performance and indoor air quality, but its potential is hindered by outdoor pollution. This paper aims to evaluate the impact of outdoor Particulate Matter 2.5 (PM2.5) pollution on natural ventilation energy saving potential in office buildings in China. Firstly, a typical office building in five representative cities across all climatic regions was designed. Secondly, related weather data were obtained and preprocessed. Thirdly, a computer model was developed under the EnergyPlus environment with smart window ventilation control, space temperature reset using adaptive thermal comfort model, and a validated pollution transportation model that calculates the indoor PM2.5 concentration. The computer model was applied to three air-conditioning systems, i.e., constant air volume (CAV), variable air volume (VAV), and variable refrigerant flow (VRF) with three evaluation indices. The results show that the natural ventilation hours rate with/without considering the outdoor PM2.5 concentration level were 15%–55% and 28%–67%, respectively. Energy savings varied across regions, with mild regions having the highest potential and cold regions having the least. CAV demonstrates the highest energy savings, followed by VAV and VRF, except in Guangzhou where VAV performs the worst. This study contributes to understanding the impact of outdoor pollution on natural ventilation potential and provides practical insights for energy-saving strategies in office buildings. Its originality lies in the evaluation methodology, comprehensive approach, sophisticated computer model, comparative analysis of air-conditioning systems, and practical implications for energy-savings. The research outcomes can guide building facility engineers in implementing ventilation control strategies while maintaining indoor thermal comfort.