Natural Ventilation Performance Research Articles

The Improvement Plan of Natural Ventilation Performance Evaluation of Residential Buildings in Green Building Certification (G-SEED)

The Improvement Plan of Natural Ventilation Performance Evaluation of Residential Buildings in Green Building Certification (G-SEED)

Statistical analysis of natural and mechanical ventilation performance in improving indoor air quality, thermal comfort, and perceived air quality in a healthcare facility

Ventilation strategies in healthcare facilities are mainly directed towards mechanical systems. Due to patients’ preferences or the necessity of terminal reheat/recool, Air Handler Units are often turned off or windows are opened when mechanical systems are active. This leads to poor IAQ, nosocomial infections, and energy loss. Besides, ventilation systems are not typically intended to optimize user satisfaction. Using field measurements in 140 spaces, survey studies, and statistical analysis, this study compares ventilation strategies in providing IAQ, thermal comfort, and Perceived Air Quality as an indicator of user satisfaction. 315 samples were collected for air velocity, air temperature, relative humidity, PAQ, odor intensity, and VOC concentrations. Lowest to highest pollutant concentrations were observed respectively in mechanical ventilation with two open windows, mechanical ventilation with one open window, natural ventilation with two open windows, mechanical ventilation with closed windows, natural ventilation with one open window, and nonventilated spaces. There was no evidence of an effect of ventilation strategies on environmental parameters and user satisfaction. Users’ thermal comfort and air quality satisfaction were not guaranteed even when ventilation rate, pollutant concentrations, and environmental parameters were within the permissible range. Findings support the efficient performance of natural ventilation in providing acceptable air quality.

Effect of rain shelter installation on the natural ventilation performance of monitor roofs

As a common means of building ventilation, monitor roofs have been employed to introduce indoor airflow via thermal buoyancy and/or wind. However, preventing rainwater from entering the room via the monitor roof has become an important practical issue. In this study, the effect of installing a rain shelter on the natural ventilation performance of a monitor roof was studied via computational fluid dynamics (CFD). The experimental monitor roof was 1.2 m in width and 1.2 m in height, with/without eave overhang. The results revealed that after rain shelter installation, a rain protection effect was achieved, and the ventilation rate increased because of flow structure conformity, with an overall average effectiveness of 1.02. The ventilation potential and the basic flow patterns corresponding to different design schemes were described in detail. Moreover, a correlation equation for the hybrid natural ventilation rate under the recommended design schemes was provided.

Acoustic Natural Ventilation Openings - OVNA : How to get rid of the impossible choice between too much heat inside or too much noise !

Due to global warming, summer comfort in buildings is a prime issue, and so is indoor air quality. Natural ventilation is encouraged by "low-carbon" approaches to cool the buildings and reduce air-conditioning. However, remaining free constructible areas in dense cities are mainly noisy, and the inhabitants should not be forced to choose between too much heat inside or too much noise ! The first step is to anticipate buildings' façades " eligibility for natural ventilation through opened windows ", depending on their exposure to the forecoming noise sources. Since 2015 LASA has been carrying R&D on " Acoustic Natural Ventilation Openings - OVNAs" which aims to bring great amounts of fresh air in the buildings, for cooling and ventilate them without allowing noise inside ! It implies to develop accurate exposure models for "noise peaks" which cause sleep or work disturbances, and anticipate the required noise reductions for each windows. On the basis of this work, and an ongoing PhD at LASA, we seized the opportunity to build two OVNA prototypes and to carry out listening sessions and acoustic/thermal measurements. Theses experiments have enabled LASA to confirm the OVNA's performances (sound attenuation, etc.) and improve the modelisation and assessing methods.

Investigation of the sound insulation and natural ventilation performance of a metamaterial-based open window

Recent advancements in metamaterials have created new opportunities to enhance indoor environmental quality (IEQ) by integrating natural ventilation and sound insulation in architectural designs. Metamaterial-based windows can facilitate natural ventilation, contributing to energy savings while also protecting against outdoor noise. However, international standards for assessing façade sound insulation typically assume all partitions are closed, with only the Danish standard DS 447:2021 accounting for partially open conventional windows. These standards do not address simultaneous noise mitigation and natural ventilation. To fill this gap, this study evaluated a prototype metamaterial-based device called the Acoustic Metawindow (AMW) unit using three experimental methods. These methods included the diffuse field method (ISO 10140 series), an adapted directive sound field method (EN 1793-6), and beamforming to control sound leakages from the AMW unit in both closed and open states. Additionally, the study used an adapted ISO 9972 method to assess the ventilation potential alongside sound insulation of the open AMW unit. The findings revealed that the AMW unit significantly outperformed equivalently open windows, achieving a sound level difference (Dn,e) improvement of 5–15 dB in the 500–5000 Hz frequency range, resulting in a total Dn,e,w of 30 dB. The study also indicated a correlation between the frequency range of effective sound insulation and the metamaterial design features of the AMW unit. This research suggests the possibility of a more inclusive standard that considers partially open sound-insulating devices as windows in the built environment, combining noise mitigation and energy saving.

Reinterpretation of Passive Cooling Strategies in Hot And Dry Climate Traditional Architecture: Vents in The Building

The building sector is among the most critical factors affecting environmental sustainability due to its impacts, such as energy consumption and greenhouse gas production. The reasons for energy consumption and greenhouse gas production in the building sector may vary according to climatic characteristics. In hot and arid climate regions, a significant portion of energy consumption is caused by indoor cooling, especially since the focus is on reducing the indoor temperature. In the periods when traditional architecture was developed, the lack of technological products that would increase energy consumption was effective in providing indoor air conditioning with passive design strategies. This study aims to identify the building openings for natural ventilation and cooling used in the traditional architecture of hot and dry climates and to analyze and evaluate their modern interpretations. A total of 235 award-winning projects were analyzed, and 21 were included in the study. In this context, it was determined that 16 different strategies used in traditional architecture were re-interpretation, and their modern interpretations were analyzed through award-winning projects. The traditional passive design strategies identified in this context have been adapted to modern architecture in 18 types. Wind orientators come to the forefront. In addition, it was determined that the strategies adapted to modern architecture are generally integrated. This study guides modern interpretations of traditional passive design strategies for sustainable building design.

Natural ventilation potential of teaching building complexes with different block shapes and layout patterns

Natural ventilation significantly enhances building energy efficiency and indoor air quality, thereby reducing virus transmission risks, especially crucial in teaching buildings on university campuses frequently occupied by large numbers of students. This study investigates the design impacts of teaching building complexes on indoor and outdoor wind environments, aiming to propose practical design recommendations. Firstly, a typological analysis of teaching building complexes from ten universities in Guangzhou University Town (GUT) was conducted, screening out several archetypes representing diverse design features. Computational fluid dynamics (CFD) simulations were then performed on 16 hypothetical teaching building complexes derived from these archetypes. The wind velocity distributions and area-weighted wind velocities across various hypothetical scenarios were compared and analyzed, allowing for a thorough assessment of the natural ventilation performance associated with different block shapes and layout patterns. The findings reveal that canyons between buildings have a marginal impact on natural ventilation within scenarios characterized by aligned layouts. In contrast, staggered layouts notably enhance natural ventilation, particularly with orthogonal prevailing winds. Furthermore, semi-enclosed courtyard blocks outperform fully enclosed courtyard blocks in natural ventilation, especially when their openings align with prevailing wind directions. Finally, several practical recommendations were summarized for achieving sustainable teaching building design in similar climate regions. Key contributions include demonstrating the significant influence of block shape and layout on ventilation performance and offering novel insights into optimizing building designs for improved natural ventilation.

Thermal and energy performance assessment of naturally ventilated roofs with phase change material

The effect of incorporating phase change material (PCM) into roofing systems combined with natural ventilation is numerically and experimentally investigated. Four roof configurations, including ventilated and unventilated options with and without an air gap between the PCM and the insulation material, are subjected to experimental research during the winter season in a semi-arid climate using two fully instrumented modules. A sensitivity analysisis conductedthrough annual transient simulations fordifferentair gap dimensions and schedule openings. The experimental campaign demonstrates a decrease in the maximum peak indoor air temperature of between 1.9 and 4.4 %when the PCM is employed. Additionally, an increase in the minimum indoor air temperature between 4.4 and 10.4 % is achieved. Similarly, an improvement in the thermal performance of the PCMis observedwhen natural ventilation occurs, and it positively influences the interiorsurface temperature of the roof.Furthermore, the numerical results show almost zero annual thermal balance in the scenario where natural ventilation is allowed in the combination of 12 and 24 h per day through ducts with a diameter of 15 and 20 cm, respectively. Finally, this demonstrates that PCMroofs enhanced with natural ventilation could be an energy-efficientalternative for semi-arid climates under well-configured ventilation schedules and roof layers.

Evaluating the Ventilation Performance of Single-Span Plastic Greenhouses with Continuous Screened Side Openings

Natural ventilation is the most cost-effective environmental control method for protected horticulture. To overcome the issues associated with high temperatures in greenhouses, analyzing their ventilation characteristics and maximizing their natural ventilation performance are essential. Therefore, in this study, the natural ventilation performance of arched single-span plastic greenhouses with screened side openings was empirically investigated. Three identical single-span plastic greenhouses were used in this study, each with different side-opening heights. Temperature and wind-speed data were collected, and the ventilation-volume flow rate was calculated considering both buoyancy and wind forces. The natural ventilation performance of the greenhouses was strongly and positively correlated with the ventilation-area ratio and outdoor wind speed. The ventilation rate increased linearly with an increase in the ventilation-area ratio and high outdoor wind speeds. However, the association between ventilation performance and indoor–outdoor temperature differences was not strong. When the ratios of ventilation areas in the greenhouse were changed to 0.08, 0.19, and 0.29, the average indoor–outdoor temperature differences were 14.0, 10.1, and 7.7 °C, respectively, and the ventilation rates were 0.0081, 0.0196, and 0.0315 m3 s−1 m−2, respectively. The proportion of wind in the total ventilation performance was high with a low ratio of ventilation openings and high outdoor wind speeds. However, the proportion of the buoyancy was high, with a high ratio of ventilation openings and a large indoor–outdoor temperature difference. Overall, this study provides foundational insights for optimizing the design and evaluation of ventilation openings in greenhouses, considering the outdoor wind speed.

Optimizing wind-catching butterfly roofs to improve cross natural ventilation performance in apartment buildings

Abstract This study aims to enhance cross natural ventilation performance in multi-level double-loaded apartments by employing a wind-catching butterfly roof, specifically designed for apartments with a center-to-center opening configuration. A 2k full-factorial design of experiment (DOE) method with a center point is utilized for design optimization. Nine configurations, determined by roof height h and roof angle α, are assessed using Computational Fluid Dynamics (CFD). After the initial DOE assessment, three additional butterfly roof designs with varying α values are explored. The dimensionless flow rate (DFR) serves as the objective function for optimization. The optimal design features a butterfly roof with h = 0.01m and α = 30°, demonstrating improvements of 2.5%−4.9% in DFR and 5.3%−9.0% in the pressure coefficient C p compared to scenarios without a butterfly roof. Butterfly roofs also increased the velocity magnitudes in the rooms of the leeward block, with configurations h = 0.01m and α = 35° and 37.5° showing the most significant increases of 58.5% − 86.9% on levels 1 to 3. The discharge coefficient C d induced by all butterfly roof configurations are within 0.6 − 0.7 on levels 1 to 3, while the C d values for levels 4 to 6 are within 0.5 − 0.6. Although butterfly roofs can enhance indoor air quality, they require further research to meet all recommended guidelines. These findings provide valuable insights for architects and urban planners aiming to reduce the environmental footprint of apartment buildings. This research presents a comprehensive evaluation of the potential of butterfly roofs to enhance apartment ventilation and offers recommendations for future design improvements.

Study on the optimal layout of roof vents and rooftop photovoltaic of the industrial workshop

Roof vents are crucial for facilitating natural ventilation within industrial workshops. However, their substantial size and height can limit available roof space and create extensive shadow areas, thereby impeding the installation of photovoltaic (PV) systems on industrial roofs. This study quantitatively assesses the influence of roof vent positioning, morphology, and roof architecture on the natural ventilation efficiency of workshops with varying indoor heat sources. Subsequently, the study evaluates how different vent configurations affect the installable area for rooftop solar panels. Findings suggest that shifting from traditional roof ridge vents directly above a heat source to north-side vents inclined towards the roof can marginally decrease the ventilation flow rate by approximately 5 %, translating to a minor temperature rise of around 0.46 °C within the occupied zone. Nonetheless, the Predicted Mean Vote (PMV) thermal comfort indices remain consistent across scenarios. Notably, adopting north-side vents, either flush with the roof or inclined, can enhance the annual energy yield of the rooftop PV system by 15.49 % and 22.67 %, respectively, under equivalent solar irradiation. Thus, strategic adjustments to vent positioning, form, and roof design can substantially boost the photovoltaic system's power output without compromising the workshop's natural ventilation performance.

Balcony design to improve natural ventilation and energy performance in high-rise mixed-mode office buildings

Balconies have the potential to promote airflow and regulate solar heat gain, which can reduce energy usage for cooling in buildings. However, designing these elements can be challenging due to complex trade-offs for natural ventilation and energy performance, highlighting the need for advanced simulation tools to guide balcony design decisions. This study aims to evaluate the impacts of balcony design on natural ventilation and thermal and energy performance in high-rise mixed-mode office buildings in São Paulo, Brazil. To this end, an integrated method that involves computational fluid dynamics (CFD) and building performance simulations (BPS) is developed to identify optimal solutions. Through this method, the performance of 40 balcony designs is studied, comprising diverse alternatives for three balcony design parameters (width, depth, and location on the façade). Furthermore, the research is performed considering the balcony effects on two façade orientations (north and south), two wind incidences (windward and leeward), and three floor levels (upper, medium, and lower floors). Results are analysed through a sensitivity analysis, percentage of change and cross-analysis. The findings indicate that narrow and shallow balconies (2 m × 0.5 m) are the best design option for the south façade; they enhance natural ventilation and reduce energy consumption for cooling across all floor levels and balcony locations. Conversely, for the north, sun-facing façade, it is recommended to use wide and deep balconies (5 m × 2 m) to reduce solar gains and associated energy consumption for cooling, despite potential limitations in natural ventilation.

Optimizing air inlet designs for enhanced natural ventilation in indoor substations: A numerical modelling and CFD simulation study

This paper investigates the ventilation and heat dissipation performance of a 110 kV indoor substation under natural ventilation conditions using computational fluid dynamics (CFD). The objectives are to evaluate the influences of air inlet design parameters including location and size, and transformer load, on the airflow distribution, temperature field, and cooling efficiency. The study finds that staggered opposite inlets optimize cooling uniformity without airflow attenuation. Compared to a single inlet, the maximum transformer temperature is reduced by 1.3 °C and energy utilization increases by 9.1 % with staggered inlets. Increasing the inlet length ratio initially improves cooling until an optimal point (The length ratio is 1.10), while reducing the inlet height ratio decreases airflow and efficiency. With load increasing, the intake airflow rises but at a reduced rate, and the temperature difference can exceed 15 °C under high loads. In summary, optimizing inlet design enhances natural ventilation performance in indoor substations, but limitations exist at high loads, indicating supplemental mechanical ventilation may be required.

A theoretical and numerical analysis of solar chimney in multi-storey atrium building

Current research efforts on solar chimney are much on those configurations with single space or single vent, hampering its applications in complex buildings. To expand its implementation, the viability of solar chimney in multi-storey atrium buildings was explored numerically and theoretically. It was known that its natural ventilation performance can fulfil the WHO requirements (i.e., 6 air change per hour, ACH) even under low solar radiation of 200 W/m2 if it is appropriately designed, such as cavity gap (d), cavity height (Hc), solar radiation (Q), and window width (W). Its natural ventilation rate was found to be positively linear to the exponential form of the analyzed factors in this study, including cavity gap (d0.63∼0.69), cavity height (Hc0.59∼0.60), solar radiation (Q0.42∼0.43), and window width (W0.14∼0.20). The impacts of cavity gap and solar radiation are relatively weaker for big space such as atrium than those scenarios with single-space ventilation in the literature. The volume of the connected space was found to affect its natural ventilation performance, where the obtained ventilation rate of 4-storey is averagely 5.1 % lower than those of 3-storey buildings. A theoretical model was developed and experimentally validated, for the first time, to predict the natural ventilation rate of solar chimney when it is applied to the atrium with multiple air inlets. It was also noticed that the same theoretical model can be applied to the atrium buildings with odd and even storeys, but the area coefficients are different. The research outcomes of this study confirm the viability of solar chimney in complex buildings and offer a theoretical foundation for its implementation.

Impact of Balcony Configuration on Natural Ventilation Performance in Indoor Spaces of Social Buildings (Rusunawa) in Indonesia

Peningkatan urbanisasi berdampak terhadap kualitas lingkungan dalam ruangan dan peningkatan konsumsi energi dalam bangunan perkotaan di Indonesia, khususnya pada bangunan Rusunawa. Meskipun menyediakan hunian terjangkau, Rusunawa menghadapi tantangan terkait konsumsi energi listrik dalam mencapai kenyamanan dalam ruangan. Implementasi pasif desain seperti balkon diharapkan mampu memaksimalkan penghawaan alami dalam ruangan. Tujuan dari penelitian ini adalah untuk mengidentifikasi pengaruh konfigurasi balkon terhadap performa kinerja ventilasi alami dalam ruangan pada bangunan rusunawa di Indonesia dengan harapan memberikan panduan dalam mengoptimalkan kenyamanan ruangan melalui ventilasi alami. Metode yang digunakan dalam penelitian ini adalah metode simulasi CFD melalui perangkat lunak Rhinocheros & Butterfly untuk menunjukan nilai performa kinerja ventilasi alami dalam ruangan. Hasil penelitian menunjukkan bahwa konfigurasi lebar dan kedalaman balkon secara signifikan meningkatkan nilai ACH dan kecepatan angin. Konfigurasi lebar balkon sebesar 40% menghasilkan peningkatan kualitas udara dalam ruangan sebesar 18-26%, sementara konfigurasi kedalaman balkon sebesar 20% menghasilkan peningkatan sebesar 9-10%.

Erratum to: Research on the influence of outdoor trees on natural ventilation performance of an academic building

Erratum to: Research on the influence of outdoor trees on natural ventilation performance of an academic building

Experimental Study of Wind Pressures on Low-Rise H-Shaped Buildings

Recognizing the urgent need for mitigating global warming, natural ventilation presents a potential strategy to reduce cooling energy demands, enhance thermal comfort, and contribute to indoor air quality. H-shaped buildings are prevalent worldwide, and they constitute the majority of the social housing construction in Brazil. Research suggests that the inadequate design of these buildings can result in poor ventilation; however, investigations about their natural ventilation performance are limited. Thus, the present contribution aims to determine the impact of the geometric characteristics of H-shaped buildings on the pressure distribution through wind tunnel experiments. Three models were tested in the wind tunnel experiments, representing different proportions. Their scales were configured to comply with the 5% obstruction limit allowed for wind tunnel testing, which was performed for 20 wind attack angles. Moreover, a scour test was carried out to allow a better understanding of the wind flow. Python scripting was developed to automate data processing, which is openly available in this paper. The results indicate that the proportion of the model influences the pressure distribution on roofs and leeward walls. Additionally, the depth of the recessed cavity affects its side surfaces and can result in a mirrored behavior on the frontal face of deep cavities (i.e., the wind direction is 45°). The model height influences the windward surfaces in its lower portion, since taller models present a recirculation vortex that modifies the pressure near the ground.

Opening configurations and natural cross ventilation performance in a double-loaded multi-level apartment building: A CFD analysis

This study investigates the impact of varied opening configurations on natural cross ventilation of a double-loaded multi-level apartment. Using computational fluid dynamics (CFD) simulations, twenty-five building models with combinations of top-top (TT), top-bottom (TB), center-center (CC), bottom-bottom (BB), and bottom-top (BT) opening configurations were analyzed in both windward and leeward building blocks. In the windward block, the BB configuration yielded the highest dimensionless flow rate (DFR) for levels 1–3, and BT was highest for levels 5 and 6. Air Exchange Efficiency (AEE) was optimal at 45–55% for TB configurations on levels 1–3, and for CC and BT on levels 4–6. Factor optimization (α) was introduced to balance DFR and AEE, favoring TB configurations for level 1–3 and BT configurations for levels 4–6. Additionally, the leeward block's ventilation was slightly influenced (±3.5%) by the windward block's configurations. Notably, the TT configuration achieved the highest α score at level 1 and TB at level 2, even with the lowest DFR. Conversely, the CC configuration, while having the lowest AEE for the first two levels, yielded the highest DFR values. Bottom inlet configurations recorded the lowest α scores for levels 3–6. The research suggests that the TT and CC configurations are the most effective for ventilation in the leeward block. The results indicate that building design can be optimized for ventilation performance at each level without significant impact to adjacent structures. This informs improved ventilation strategies in high-rise buildings, emphasizing design adaptability to enhance indoor air quality.

Simulation of natural ventilation for semi-enclosed buildings

Energy-saving buildings have become a topical issue and widely used the energy-saving ventilation design, which aims to maximize the use of natural ventilation while reducing demand on mechanical ventilation. In this research, natural ventilation performance of two different semi-enclosed building layouts, "O" type and "L-L" type, are studied by numerical simulation. According to the simulation results, in the "O" type, the maximum indoor air velocity occurs in building A (orientation facing the inflow direction). The minimum indoor air velocity occurs in building C (orientation facing building A). In the "L-L" type, the maximum indoor air velocity occurs in building A (orientation facing the inflow direction). The minimum indoor air velocity occurs in buildings B and D (orientation parallel to the inflow direction). And air flow field simulation results show that, the "L-L" type exhibits better than the "O" type in natural ventilation. Furthermore, simulation results show that the natural ventilation performance in the room is influenced not only by the building orientation, but also by the window size.

Natural Ventilation and Indoor Air Quality in Domestic School Building: CFD Simulation and Improvement Strategies

Natural ventilation is a process of replenishing used air from the interior environment with fresh outer air without the use of mechanical equipment. This project aims to investigate the feasibility and performance of implementing natural ventilation in dilapidated classroom designs of actual geometry. Computer models of an existing classroom were created using SOLIDWORKS based on real-scale building floor plans, while the same software was applied to compute flow simulation studies to visualise the airflow pattern, temperature distribution, relative humidity, and the thermal comfort level of occupants in the classrooms. Estimated climate parameters were input in the simulation process to illustrate better the effect of hot and humid climate conditions in Malaysia towards the thermal comfort level of occupants. In this project, a visualised wind tunnel was created to simulate the prevailing wind source that supplies wind to the designed classroom, and the airflow pattern across the designed building was analysed. From the initial simulation results, it was discovered that the airflow into the classroom is uneven, whereby some locations in the building are experiencing extremely low wind breeze, which eventually affects the comfort level of occupants in the room. On the other hand, an internal analysis focusing on the interior comfortability of the classrooms was applied to examine the thermal comfort condition while using the naturally ventilated classrooms. Recommendation optimisation approaches such as the louvre angle and introduction of a windcatcher was presented in this project to improve the natural ventilation performance of the designed classroom.