Natural Ventilation Potential Research Articles

Influence of building orientation and thermal mass configuration on the prediction of Natural Ventilation Potential (NVP) of various climates of India.

Natural ventilation potential (NVP) of a climate is a theoretical basis, and it gains importance due to the promising need for building energy conservation while conceding required thermal comfort conditions. A modified NVP analytical model is proposed by considering parameters involved in the earlier models (Yang et al., Build Environ 40:738-746, 2005; Luo et al., Build Environ 42:2289-2298, 2007). The effect of the dynamic thermal behavior of the wall/roof and building orientation on the indoor air temperature has been evaluated. The analytical model is applied to 11 major cities of India that belong to composite, hot-dry, temperate, and warm-humid climates. Five different envelope configurations are analyzed to envisage the NVP of concern climate (ED-I to ED-V). The results show that the effect of dynamic thermal response factors on the NVP is significant, and optimization of thermal response factors in addition to the U-value is mandatory. The impact of wind frequency on the selection of building orientation is substantial since it influences the total heat gained by the building envelope. Moreover, it is perceived that the optimum building orientation is independent of the climate and weather conditions. ED-II and ED-III are energy-efficient envelopes for composite, temperate, warm-humid, and hot-dry climates. The results revealed that the Mumbai climate has the highest NVP of 66% while the building is oriented in an E-W direction, and the lowest is observed for Jodhpur, i.e., 44% of the year when the building is in the NE-SW direction. The model helps the building architectural designers envisage the true NVP and assess the suitability of the building for natural ventilation.

Comprehensive evaluation of natural ventilation potential of buildings in urban areas under the influence of multiple environment-related factors

Realistic natural ventilation potential estimation is critical for energy-efficient building design. For buildings in urban areas, evaluations using design expectations tend to overestimate potential. This study presents a comprehensive framework and corresponding method to predict the natural ventilation potential of buildings, integrating multiple key environmental factors of climate features, local wind status, and air pollution level. It addresses their complex interplay. Climate impacts are evaluated through simulating using a pre-set natural ventilation rate. Computational fluid dynamics models typical neighbourhood wind fields, giving empirical wind pressure coefficient distributions by layout and wind direction to enable real-time ventilation rate calculation. Substituting real-time for pre-set rates, the natural ventilation potential considering the community layout can be obtained. Based on the data-driven rapid pollutant prediction model established in the previous study, the predictions of the temporal and spatial distributions of particulate matter can be obtained. Filtering excessive pollution periods yields air quality-integrated potentials. Natural ventilation potentials are compared under different analysis scenarios for a case-study building. Hotter climates and more frequent heatwaves lower the potential. Morphology-based potentials are significantly lower than design expectations using constant ventilation rates. Deteriorating urban air quality also directly limits ventilation use, substantially decreasing potentials when filtering for poor conditions. By capturing complex environmental interactions, this research provides a robust platform to reveal localization potentials and limitations.

Impact of climate change on the potential of free-cooling strategies for a retrofitted building in a hot climate

This paper’s objective and novelty is to understand the impact of different natural ventilation strategies as well as the effect of a proposed smart controlled ventilation strategy on cooling energy saving and thermal comfort in a residential building. Afterwards, an investigation of the Climatic Potential of Natural Ventilation (CPNV) in hot and dry climates, and particularly the potential of the night ventilation strategy under present and future climates, was made. Two prediction climate change scenarios, RCPs 2.6 and 8.5, were considered for two periods. The results, obtained by a validated simulation, have shown the beneficial effect of night ventilation, since it could reduce cooling load by 9% and would keep the operative temperature below 30°C. Nevertheless, the potential of this natural ventilation strategy would be reduced in the future due to climate change. Indoor overheating has been projected to increase drastically. The summer thermal behaviour will be greatly aggravated in the future. Indeed, the CPNV in the summer nights will be decreased by 25%. However, the climate change will affect the winter natural ventilation potential in the future. The results also highlighted that the annual Total Climatic Potential of Natural Ventilation could be increased by 1% for RCP 2.6 and decreased by 4.9% for RCP 8.5.

Natural Ventilation Potential of Residential Buildings in China Considering the Combined Effect of Indoor and Outdoor Air Pollution

With its rapid economic development, China has had to confront the serious issues of high energy consumption and air pollution. Natural ventilation is regarded as an effective method to reduce building energy consumption, but it is largely influenced by indoor and outdoor air pollution. However, most of the previous studies estimating natural ventilation potential (NVP) in China do not consider air pollution. This research estimated the NVP for residential buildings in major cities from four climate regions in China (Guangzhou, Chengdu, Shanghai, Beijing, and Shenyang) while considering the combined effect of indoor and outdoor air pollution. We compared the yearly NVP in three different scenarios, namely without considering air pollution, only considering outdoor air pollution, and considering both outdoor and indoor air pollution. The results show that Guangzhou had the highest yearly NVP, followed by Shanghai, Beijing, Shenyang, and Chengdu. The impact of air pollution could reduce the annual NVP in China by 78–95%. In addition, the main factors causing a low NVP differed between the four cities. The key factors for Chengdu and Guangzhou were natural ventilation flow rate and indoor air pollution, respectively. Beijing and Shenyang were mostly influenced by outdoor air pollution. Shanghai had two main factors with similar influence degrees, namely outdoor air pollution and indoor air pollution. The findings of this study will guide architects and policymakers in better forming natural ventilation strategies.

Assessing effects of future climate change on outdoor thermal stress and building energy performance in severe cold region of China

Future climate change is poised to affect the urban thermal environment and building energy performance in the severe cold region, yet its full impact remains unclear, particularly concerning extreme weather events. This study proposes a multi-scale climate-energy framework to assess the future climate's influence on outdoor thermal stress and building energy efficiency under Shared Socioeconomic Pathways for 2050 and 2080 in this region, using Harbin serving as a case study. The framework also evaluates the adaptation potential of trees and natural ventilation. The results showed that climate change may narrow the physiologically equivalent temperature (PET) range in summer daytime, and increase unacceptable heat exposure duration from 2 h to 7–8 h by 2050 and further to 5–10 h by 2080. While the overall annual building energy demands are expected to increase minimally (<12 %), cooling loads could rise substantially. Trees show diminishing returns in reducing peak PET as climate severity increases, yet can moderately reduce total energy demand (4–6 %) and peak demand (4–5 %) during extreme warm days. The energy-saving potential of natural ventilation is projected to decline, with a potential decrease of up to 40 % by 2080 in the most severe scenario. This study provides new insights into how future climate change could impact outdoor comfort and building energy in the severe cold region, and offers a versatile framework for urban sustainability planning that can be applied to other cities and climates.

Predicting climate change and occupants’ behaviour impact on thermal-energy performance of global south housing: Case study in Brazil

Due to climate change conditions, natural ventilation potential may reduce over the years and increase dependence on HVAC systems. Moreover, occupants’ behaviour regarding natural ventilation is a significant parameter affecting the thermal-energy performance of residential buildings as people tend to occupy their homes differently depending on their life, work and cultural routines. Therefore, in this study, the thermal-energy performance of a Global South (GS) housing case study located in Brazil was assessed in a future weather context. This paper included two major steps: (1) Optimization procedure to create optimized models based on different occupancy patterns; and (2) Parametric analysis to explore the building’s thermal-energy performance for a given constructive design option, occupant behaviour and weather data. The optimization procedure included a multi-objective optimization based on the Non-dominated Sorting Genetic Algorithm II (NSGA-II) to minimize discomfort hours and cooling energy demand, while parametric analysis explored the occupants’ behaviour varieties derived from alternative occupancy patterns, ventilation availabilities and HVAC operation modes. The obtained future context simulation results indicated an increase in discomfort hours and cooling energy demand, while the most appropriate architecture design might vary depending on the occupancy behaviour.

Shading Performance of Public Open Spaces: A Multi-Criteria Evaluation Framework for Housing Projects

This study investigates the impact of building grouping patterns on enhancing shading in public open spaces, considering different solar orientations, housing densities, and the hot climatic conditions of Saudi Arabia. The study considered a set of environmental performance indicators, including the percentage of open space shaded areas, heat gains through the building envelope, open space surface temperature, and the natural ventilation potential of each grouping pattern of the buildings. The results showed that at a building height of five floors, the percentage of open space shaded areas ranged from 14% to 53%. However, using the suggested multi-criteria evaluation framework to consider the above-mentioned performance indicators revealed more in-depth observations. Configurations that included parallel rows of buildings staggered and centralized in the middle of the site offered the best performance in this regard. This shows that compact grouping patterns in which open spaces are decentralized offer more urban shading and protection against undesirable heat gains through the building envelope during summer. The results of this study will enable a wider exploration of different building grouping patterns, which are needed in the harsh hot climate of Saudi Arabia to respond to current rapid housing development plans.

Influence of cross-ventilation cooling potential on thermal comfort in high-rise buildings in a hot and humid climate

The rising cooling energy demand, caused by the increase in global average temperature and the frequency of heat waves, is currently leading to a significant increase in global electricity consumption. Passive cooling strategies, such as ventilative cooling, can provide acceptable indoor thermal comfort with no or minimal energy consumption, offering an alternative to air conditioning systems in buildings. This paper investigates the effectiveness of natural ventilation in an iconic post-modernist high-rise building in India: Charles Correa's Kanchanjunga Apartments. The research, employing CFD simulation paired with building energy simulation, demonstrates how cross-ventilation can improve the ventilative cooling efficiency in buildings, ensuring affordable indoor thermal conditions even in adverse climatic conditions like the Indian one. Thanks to night-time structural cooling, a maximum reduction in the operative temperature of up to 5.3 °C was achieved compared to the scenario without natural ventilation and up to 6.4 °C compared to the outdoor temperature peak on the hottest day. Consistently with the Indian Model for Adaptive Comfort, cross-ventilation ensures a reduction in discomfort hours of up to 58 % on the hottest day and a total reduction in discomfort hours on a typical monsoon and winter day. The paper aims to assist architects and policymakers in quantifying the cooling potential of natural ventilation in high-rise buildings, suggesting passive solutions for cooling energy saving.

Exploring the natural ventilation potential for supertall buildings considering vertical meteorology: A case study in Harbin, China

The natural ventilation strategy is gaining increasing attention from architects due to its advantages in reducing energy consumption and maintaining a healthy indoor environment. For supertall buildings, the vertical variation in outdoor meteorology has inspired us to explore the energy-saving potential by adopting natural ventilation strategy. This study investigates the impact of vertical variation in urban meteorology on the natural ventilation potential (NVP) of supertall buildings based on numerical simulation and field observation. Firstly, the Weather Research and Forecasting (WRF) model is used to simulate the urban meteorology of the study region by integrating the local climate zone (LCZ) map. Next, meteorological data from sounding experiments by unmanned aerial vehicle (UAV) and monitoring stations are used to validate the simulated result, and thereby to explore the vertical meteorology in urban area. Finally, the vertical NVP in supertall buildings is quantitatively assessed considering the impact of LCZ in urban areas based on thermal comfort models. The findings reveal that atmospheric temperature decreases approximately linearly with increasing altitude, with a maximum temperature gradient of up to −0.82 °C/100 m. Static models underestimated the annual natural ventilation hours (NVHs) by at least 348 h compared to the adaptive thermal comfort model. Compared to low-density building regions, the higher NVP is indicated in high-density building regions. This study aims to illustrate the importance of considering the vertical variations of urban meteorology, and is expected to assist architects and policy makers in quantifying the energy saving potential of natural ventilation in supertalls.

Development of window scheduler algorithm exploiting natural ventilation and thermal mass for building energy simulation and smart home controls

Building energy simulations often rely on abstract assumptions when it comes to natural ventilation, such as ‘windows always open [or closed]’ or ‘windows open when outdoor temperature is below a certain threshold.’ However, simulations based on these assumptions fail to fully exploit the cooling potential of natural ventilation, as its effectiveness can be enhanced or diminished by various factors, including the presence of thermal mass. This issue also extends to smart home controls, where determining the window schedule becomes challenging without information about the building's response to outdoor conditions. To address these issues, this study has developed an analytical model for window operation schedules that leverages the passive cooling from natural ventilation. The analytical model was validated against a Modelica simulation. A case study utilizing the BESTEST model of ANSI/ASHRAE Standard 140 underwent validation with EnergyPlus simulations, showing strong concordance. The algorithm provides window schedule recommendations adapted to various airflow rates, thermal masses, and climate variations. The case study demonstrated that proper window scheduling could reduce indoor temperature by up to 8 °C under the given simulation settings, thereby improving resilience and indicating potential energy savings. Furthermore, the paper explores the potential opportunities and challenges this approach presents, especially for building simulation and smart home applications.

Energy consumption behaviors and the potential of natural ventilation emission reduction in residential building

ABSTRACT China is the largest Carbon Emissions country in the world. The data analysis and simulation of the sampled residential buildings reveals that there exists a large gap between the monitoring data and energy simulation. Based on the thermal comfort theory, we further explored the relationship between the energy consumption behaviors of residents and building ventilation emission reduction. This study constructed a questionnaire to analyze the use habits of existing residential buildings and equipment. The results show the range of suitable outside temps. In this paper, the findings of the survey were combined with the probability of summer outside temp range profiles to derive the thermal comfort satisfaction of the sample population. In the summer high temperature environment, natural ventilation can help to reduce indoor temperature and reduce the concentration of pollutants in the indoor air, thereby improving indoor air quality and reducing energy consumption. The findings can evaluate the emission reduction potential of natural ventilation. The study provided directions for the implementation of low carbon natural ventilation in residential buildings: natural ventilation can be used to reduce residential energy consumption and carbon emissions, reducing the need for mechanical ventilation. This enables environmentally friendly and sustainable buildings and uses renewable energy sources such as solar and geothermal energy as an energy supply. In addition, the study examined the emission reduction potential of natural ventilation measures in the summer temperature range of 26°C to 28°C, which could reduce carbon dioxide emissions by 1.61 kg per square meter.

Impact of building density on natural ventilation potential and cooling energy saving across Chinese climate zones

Natural ventilation is an energy-efficient approach to reduce the need for mechanical ventilation and air conditioning in buildings. However, traditionally weather data for building energy simulation are obtained from rural areas, which do not reflect the urban micrometeorological conditions. This study combines the Surface Urban Energy and Water Balance Scheme (SUEWS) and EnergyPlus to predict natural ventilation potential (NVP) and cooling energy saving in three idealised urban neighbourhoods with different urban densities in five Chinese cities of different climate zones. SUEWS downscales the meteorological inputs required by EnergyPlus, including air temperature, relative humidity, and wind speed profiles. The findings indicate that NVP and cooling energy saving differences between urban and rural areas are climate- and season-dependent. During summer, the urban-rural differences in natural ventilation hours are −43% to 10% (cf. rural) across all climates, while in spring/autumn, they range from −7% to 36%. The study also suggests that single-sided ventilation can be as effective as cross ventilation for buildings in dense urban areas. Our findings highlight the importance of considering local or neighbourhood-scale climate when evaluating NVP. We demonstrate a method to enhance NVP prediction accuracy in urban regions using EnergyPlus, which can contribute to achieving low-carbon building design.

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.

Shape optimization of high-rise solar chimneys to improve the uniformity of flowrate distribution

Solar chimneys (SC) are passive ventilation devices which can induce natural ventilation by utilizing solar radiation. Many studies of SCs have focused on single-storey or low-rise buildings, but much less attention has been given to SCs for high-rise buildings. This paper investigates the airflow induced by 10- to 50-storey SCs using an experimentally validated computational fluid dynamics (CFD) model. The effects of the total number of storeys and the air gap size on the induced average flowrate were first studied, and their correlations were derived through linear regression. The flowrate induced by a conventional SC with a constant air gap size is highly non-uniform. To improve the uniformity of flowrate distributions among storeys, a taper structure with a narrowing air gap downwards was proposed for multi-storey SCs. Numerical simulations show that adopting the taper structure can significantly improve the uniformity of flowrate distributions. For example, in a 20-storey SC, the flowrate difference between the maximum and minimum among the middle 17 storeys, normalised by the average, decreases from 122.8% to only 15.8% when the taper structure is adopted. A parametric study of 441 numerical simulation cases was conducted to derive the optimum ratios of the bottom gap size to the top gap size for taper multi-storey SCs. The results of this paper can provide guidance on how to design multi-storey SCs for high-rise buildings to exploit the potential of natural ventilation and reduce energy demand for cooling and ventilation.

The Effect of Window Placement on Natural Ventilation Capability in a Jakarta High-Rise Building Unit

The purpose of this study was to investigate the natural ventilation potential in an apartment unit in a high-rise building. A corner unit of a two-bedroom apartment was selected for this study, where single-sided and cross ventilation occurred in the unit. This study employed a CFD simulation to model the indoor airflow of an apartment unit in West Jakarta. The units were modelled and simulated using CFD with a RANS k-ε turbulence model. The results were validated with the readings from the field measurements that had been conducted. Based on CFD results, the window position influences indoor airflow. In the case of cross ventilation, a windward opening is more beneficial, while in single-sided ventilation, a leeward opening creates more indoor airflow. Therefore, it is recommended that the characteristic of window design be considered in the early design stage not only to improve indoor air quality but also to maintain privacy and safety measures.

Natural ventilation versus air pollution: assessing the impact of outdoor pollution on natural ventilation potential in informal settlements in India

Despite the proven benefits of natural ventilation (NV) as an effective low-carbon solution to meet growing cooling demand, its effectiveness can be constrained by poor outdoor air quality. Here, we propose a modeling approach that integrates highly granular air pollution data with a coupled EnergyPlus and differential equation airflow model to evaluate how NV potential for space cooling changes when accounting for air pollution exposure (PM2.5). Given the high vulnerability of low-income populations to air pollution and the dearth of energy and thermal comfort research on informal settlements, we applied our model to a typical informal settlement residence in two large Indian cities: New Delhi and Bangalore. Our results indicate that outdoor PM2.5 levels have a significant impact on NV potential especially in highly polluted cities like New Delhi. However, we found that low-cost filtration (MERV 14) increased the NV potential by 25% and protected occupants from harmful exposure to PM2.5 with a minor energy penalty of 6%. We further find that adoption of low-cost filtration is a viable low-carbon solution pathway as it provides both thermal comfort and exposure protection at 65% less energy intensity—energy intensity reduced to 60 kWh m−2 from 173.5 kWh m−2 in case of adoption of potentially unaffordable full mechanical air conditioning. Our work highlights ample opportunities for reducing both air pollution and energy consumption in informal settlements across major Indian cities. Finally, our work can guide building designers and policymakers to reform building codes for adopting low-cost air filtration coupled with NV and subsequently reduce energy demand and associated environmental emissions.

Evaluation of building arrangement on natural ventilation potential in ideal building arrays

ABSTRACT Nowadays, the process of urbanization is accelerating, and the density of buildings is increasing rapidly. Natural ventlation is an energy-saving way of building ventilation and to solve the issue of building overheating. The buildings are all considered as cubes and their arrays are evenly distributed. The results from nearly 100 cases show density is the main factor in uniform arrays and not much difference between the staggered and normal arrangements if consider a year. The method can reflect the ventilation capacity of the buildings, which is somewhat inverse to the air age but different meaning. It can be used to guide the layout and planning in early design stage.

A Literature Review on Methods and Metrics for the Analysis of Outdoor Air Displacement Conditions in the Urban Environment

The ongoing pandemic has driven the attention of both policy makers and professionals of the building sector towards the need for proper ventilation of the indoor environment. Despite accurate ventilation control only being available with mechanical ventilation systems, in several countries worldwide the renovation of indoor air relies mainly on natural solutions. In this context, in the design of new or renovated buildings, conventional natural ventilation rates are typically assumed to be in agreement with available technical standards, sometimes regardless of the actual external conditions. For instance, local wind speed and direction, as well as buoyancy-driven air displacements, are not considered, even if they can significantly affect the ventilation efficacy for the designed buildings. Moreover, the local outdoor temperature and the presence of pollutants are rarely accounted for, even though they can represent interesting inputs not only for naturally ventilated buildings but also for mechanical ventilation systems. In the framework described above, this review paper aims to provide an overview of the current state-of-the-art of the research regarding air displacement and conditions in the urban context, focusing on the main methods, parameters and metrics to consider in order to ensure a deeper and more accurate modelling of natural ventilation potential in the urban built environment. The analysis of the literature includes both experimental and numerical studies. As regards the latter ones, the features of the chosen urban areas—real or parametric ones—the adopted turbulence models and the indexes calculated as simulation outputs were analysed, with the purpose of defining a common framework to support future extensive numerical studies.

Investigation of Airflow for Natural Ventilation in the Typical Medium-Rise Housing Cluster in South-Eastern Nigeria

Wind driven natural ventilation dependents on the microclimate conditions of its environment to thrive. In urban streets, it is influenced by the wind velocity and air temperatures factors. In this study, field experiments were carried out in selected streets of a typical medium rise housing cluster in southeastern Nigeria. The aim of the study was to understand the characteristics of air flow within this housing category, and to better examine the potentials of wind driven ventilation in this class of settlement. Wind speed and directions in the middle of selected streets were measured. Respectively, the undisturbed climatic conditions above the street canyon were recorded as well. The overall conclusion at the end of the study is that inside the streets, the potential of natural ventilation for both the single type and multi-branch type configurations is reduced, while that of continuous street configuration (without intermediate intersections) provided a higher potential for natural wind driven ventilation. This is attributed to the internal interferences and reduction of the wind speeds inside the street canyons. Generally, universal meteorological information gotten from unobstructed areas in cities are used in the design of buildings, thus the significance of this study outlines the importance of obtaining microclimatic information in pre-design stages.

Multi-scale climate-sensitive planning framework to mitigate urban heat island effect: A case study in Singapore

This study developed a climate-sensitive planning framework to assess Urban Heat Island (UHI) intensity and wind potential, and apply assessment results into urban planning practice. Multi-scale environmental assessments and mitigation were interlinked from the urban design perspective. Three steps are conducted: (1) UHI intensity assessment to identify hot spots, (2) urban wind assessment to evaluate mitigation potential, and (3) urban design implications. A case study in Singapore was conducted to demonstrate the application of the framework. Geographic Information System-based tools that are accessible to designers and planners were used to conduct a coherent assessment-mitigation planning workflow. The empirical model between sky view factor and air temperature increment was modified by local data to be applied in Singapore. East Singapore, with a UHI intensity of 3 °C to 4 °C, was identified as the hot spot of UHI. Natural ventilation potential of the identified area was evaluated, and air paths were identified through urban permeability map based on frontal area density calculation. Climate-sensitive urban design prototypes were thus proposed by balancing climate considerations and urban planning complex (i.e., site structure, density distribution, land use pattern). Research outputs from this study increase the engagement of climate considerations in the decision-making of urban design process.