Particulate matter (PM) pollution within subway systems poses a potential threat to passenger health. Traditional 3D computational fluid dynamics (CFD) simulations using dynamic mesh technology offer high accuracy but incur substantial computational costs, making multi-scenario parametric optimization impractical. This paper proposes a rapid calculation model for PM concentration on subway platforms based on a 2D reduced-dimensional flow field and equivalent PM emission rates. By simplifying complex 3D flow fields into equivalent 2D planes and correcting PM source terms based on train operating conditions, the model significantly reduces computational costs. To validate the model's application value, multi-scenario simulations were conducted for the height of platform screen door (PSD) vents, and a continuous surrogate model was constructed using Gaussian Process Regression (GPR). The results indicate that while maintaining high consistency with 3D simulation results (with errors within allowable ranges), the model improves computational efficiency by 98%. The GPR surrogate model identified an optimal vent height of 0.50 m, which balances PM control with ventilation energy savings. This study provides an efficient numerical tool for real-time monitoring and structural topology optimization of subway ventilation systems.

The application of radiative cooling materials in buildings can effectively improve the indoor thermal environment in summer. This study used computational fluid dynamics (CFD) simulation to investigate the impact of transparent radiative cooling (T-RC) film on the indoor thermal environment of an office building in Nanjing, Jiangsu Province, China. The window-to-wall ratios (WWR) and orientations of the windows were also considered. The simulation results indicate that the best cooling effect of the T-RC film on indoor average air temperature is observed in the south room (1.91 °C), followed by the east room (1.59 °C) and then the west room (1.5 °C), while the cooling effect in the north room is limited (0.56 °C). The cooling effect of the T-RC film is best in the west room at WWR 50 %, while in the east and south rooms at WWR 75 %. The cooling effect of applying the T-RC film only to the south-facing windows is 61.4 % and 57.9 % of applying film to all windows for the west and east rooms, respectively. This study can provide a reference for the effects of applying the T-RC film to office buildings, inform the design or retrofit scheme of building windows, and provide helpful information for making a more comfortable indoor thermal environment.

Urban Building Energy Modeling (UBEM) is indispensable for urban renewal, green urban design, and low-carbon energy planning. However, existing tools face significant bottlenecks regarding the feasibility of mega city-scale simulations, high technical barriers, and automated data processing capabilities. This study introduces the Calculator for Urban Building Energy (CUBE), a fully open-source platform designed to overcome these limitations. Comprising six integrated tools, CUBE streamlines automated physical modeling, parallel simulation, data analysis, and spatial visualization. Robust mega-scale model generation is achieved through adaptive geometric simplification and automated topological overlap repair, while multithreaded computing effectively accelerates simulation speeds. The platform's efficiency is validated through empirical case studies of two Chinese megacities: Beijing (0.55 million buildings) and Shanghai (0.69 million buildings). These applications demonstrate CUBE's capability to quantify correlations between urban morphology and building energy consumption across different climate zones, as well as to evaluate the energy-saving potential of radiative cooling materials. By providing public access to all source codes and executables, CUBE establishes a highly extensible framework, enabling researchers to adapt the underlying architecture and integrate novel functionalities for customized urban-scale energy simulations.

Urban overheating has intensified pedestrian heat exposure in street canyons, while the combined effects of cool material coatings and vertical greening remain insufficiently quantified. This study developed a three-dimensional computational fluid dynamics framework coupling radiation, species transport, porous media, and canopy evapotranspiration models to evaluate wind speed, air temperature, water vapor mass fraction, and the Universal Thermal Climate Index (UTCI). The constituent sub-models were validated separately against relevant experimental or benchmark data. The effects of mitigation strategy arrangement, canyon aspect ratio, solar radiation, background temperature, relative humidity (RH), leaf area density, and minimum stomatal resistance were systematically examined. The simulated field patterns showed limited airflow and humidity changes in the cool-material-only case, whereas cases containing vertical greening exhibited lower air temperature, higher humidity, and modified pedestrian-level airflow. Under the baseline hot-weather conditions, with an aspect ratio of 2, direct and diffuse solar irradiance of 800 and 150 W m-2, an air temperature of 318.15K, and a relative humidity of 20%, the configuration combining equal façade areas of cool material coatings and vertical greening reduced path-average UTCI by 1.65K on the leeward side and 2.27K on the windward side compared with the untreated canyon. Decreasing leaf area density increased path-average UTCI, whereas decreasing minimum stomatal resistance reduced it. The findings are conditional on the tested steady state conditions, perpendicular inflow, and fixed solar configuration.

Anthropogenic heat, such as heat generated by air-conditioning systems, has an essential impact on the urban wind-thermal environment in hot-summer and cold-winter regions. This study investigated the effects of anthropogenic heat on ambient air temperature and pedestrian-level ventilation rate across different seasons using CFD simulations based on six typical residential neighborhoods in Nanjing, China. The results indicated that the effects of anthropogenic heat on the wind-thermal environment of residential neighborhoods was more significant in summer. In summer, air-conditioning operation increased the pedestrian-level ventilation rate by up to 87.6%, whereas in winter, it slightly reduced the pedestrian-level ventilation rate by up to 46.5%. Anthropogenic heat created air temperature differences between the pedestrian level within residential neighborhoods and the atmospheric level. High-rise, slab-type building neighborhoods experienced less impact from anthropogenic heat. In summer, the probability of an air temperature difference below 0.5 K was 35.0%, while in winter, it was 27.5%. In addition, ambient air temperature differences were found to correlate with building density but not related to floor area ratio, surface area ratio, and sky view factor. These findings can provide a valuable reference for residential building design to mitigate the negative impacts of anthropogenic heat in Nanjing.

Indoor respiratory airborne particles pose a significant threat to public health, especially in high-occupancy office spaces. In this study, Computational Fluid Dynamics simulations were conducted to investigate the transport characterization of airborne particles from nasal breathing under displacement ventilation (DV) with factors including air change rates (ACH), relative humidity (RH), diffuser configurations, and partition designs. The modified Wells-Riley model was used for risk quantification. Results indicate that under low-velocity DV, particles exhibit limited horizontal spread but accumulate vertically, forming bimodal distributions around 1.1 m and above 1.5 m. Under the baseline condition (5 ACH, 22 degrees C supply air temperature and 50 % RH), infection risk was significantly higher at standing height (1.6 m) than at seated height (1.15 m), with the maximum probability rising from 30.98 % to 60.48 % over 1800 s. Increasing ACH significantly enhances particle removal, while RH has minimal influence. Optimized diffuser placement and larger outlet areas were found to improve airflow distribution and reduce pollutant accumulation. Critically, while partition types have limited effect on airborne particle transmission, raising partition height from 30 cm to 70 cm cuts particle suspension by 42.5 % and increases deposition nearly 45-fold, demonstrating partition height greatly limits particle transmission. The study highlights the critical role of ventilation parameters and partition designs in DV offices. The findings offer concrete guidance for designing safer offices, prioritizing optimized ventilation and partitions of at least 50 cm in height to mitigate airborne particle transmission risks under real breathing conditions in DV offices.

Dual mode thermal regulating materials have emerged as a promising strategy for reducing the seasonal mismatch of conventional building envelope materials, which often provide cooling benefits in summer but cause heating penalties in winter. This review systematically examines dual mode thermal regulating materials for building envelopes from the perspectives of mechanisms, performance evaluation, climate applicability, durability, environmental impact, and practical implementation. Based on 126 peer reviewed articles, the reviewed systems are classified into passive stimulus responsive materials, active regulation systems, and hybrid systems. Active regulation includes both externally controlled chromic materials and structurally switchable systems. Their working principles are discussed in relation to solar absorptance, solar transmittance, longwave thermal emittance, and envelope heat transfer. Particular attention is given to the different evaluation requirements of opaque envelopes and transparent envelopes, as well as the climate dependence of annual heating and cooling performance. The review shows that current studies have progressed from material level optical switching to building oriented energy assessment, but standardized parameters, long term outdoor durability, environmental safety, and construction scale validation remain insufficient. Future research should prioritize climate specific design criteria, comparable performance reporting, and integration strategies that connect material functionality with realistic building operation.

Anthropogenic heat emitted by air-conditioning (AC) outdoor units (ACAH) accumulates in poorly ventilated street canyons (e.g., perpendicular approaching winds), resulting in deterioration of the wind-thermal environment. Previous studies have usually focused on ACAH emissions at the neighborhood scale, simplifying the AC outdoor units into a continuous, strippedshape surface heat source without considering the influence of factors such as exhaust parameters and the geometric form of outdoor units, thereby hindering a deeper understanding of the mechanisms by which ACAH affects wind-thermal environments. Taking the T-shaped street canyon as an example, this study utilizes computational fluid dynamics (CFD) simulation to investigate the effects of varying exhaust wind temperatures and velocities, different layouts, and various types of outdoor units on airflow, air temperature, and velocity distribution. The results showed that as the exhaust temperature increased, the average wind speed in the horizontal direction at the center of the street canyon decreased continuously. The average temperatures in the vertical and horizontal directions at the center of the street canyon, where PTHP outdoor units were placed on the leeward side, were 7.42 K and 4.47 K higher, respectively, than those on the windward side. The street canyon temperature was lowest when central air-conditioning outdoor units were arranged. This study provides a reference for developing strategies to discharge ACAH in street canyons, offering helpful information for creating a comfortable outdoor environment and mitigating the urban heat island.

Heating, ventilation, and air-conditioning (HVAC) systems in subway stations are highly energy-intensive, making the utilization of piston wind for natural ventilation a key strategy for energy conservation. However, traditional three-dimensional (3D) computational fluid dynamics (CFD) simulations are computationally expensive and difficult to integrate with building energy simulation tools. This study proposes an efficient CFD-TRNSYS coupling framework based on information entropy-guided dimensionality reduction. First, the 3D CFD model is reduced to a 2D model using information entropy analysis. This approach preserves mass flow conservation while reducing computational time by more than 99%, with piston wind mass flow rate error controlled within 5%. The resulting 2D model demonstrates significantly higher accuracy than the conventional 0D theoretical model based on the Bernoulli equation. The dynamic piston wind data obtained from the reduced-order model are then coupled to TRNSYS for annual energy consumption simulation of a typical Shanghai subway station. Comparative results show that piston wind alone reduced the annual HVAC energy consumption by approximately 9.0%. When combined with PCM-based fan-assisted nighttime cold storage, the total energy-saving rate increased to 11.1% under the default PCM configuration and further reached 13.5% after optimizing the PCM melting temperature and thickness. Sensitivity analysis further identifies the significant influence of PCM melting temperature and thickness on overall energy-saving performance. This study provides a multi-scale coupling engineering analysis tool that balances accuracy and efficiency, offering a practical solution for energy-efficient design of subway stations.

Characterizing wind drag amidst heterogeneous urban textures and directional effects is a fundamental necessity that provides the basis for urban porous media models. This work investigates a realistic residential district (170 ha; 252 slab-shaped or irregular buildings) in Hexi New Town, Nanjing, China. Computational fluid dynamics simulations across 16 directions are performed utilizing the 3D steady RANS equations. Canopy-averaged velocity, aerodynamic drag, and volumetric drag coefficients (Cd) roses are analyzed for each neighborhood. Equations governing the drag-velocity relationship are adopted to reconstruct velocities, defined here as dragVRM method, and are also applied to estimate velocity time series. Results indicate that, considering diverse shelter effects at district and neighborhood levels, the examined high-rise (up to 57 m) low-to-mid density neighborhoods exhibit normalized C & lowast;d values ranging from 0.05 to 1. The Cd roses show significant anisotropic features, yielding an average coefficient of variation of up to 52%. The drag-VRM reproduces slightly lower average velocities, though larger discrepancies arise for irregular layouts and low ambient wind conditions. Further discussion reveals that the 300 m urban tile zoning method offers morphological and aerodynamic characterizations comparable to the neighborhood approach. Notably, the relationship between C & lowast;d and frontal area density (1f) for these realistic zones deviates from patterns in idealized urban configurations, underscoring the necessity of verifying drag models when applied to complex, local urban contexts.

The development of new low-environmental impact materials is part of sustainable development objectives and offers an interesting alternative to promote building hygrothermal comfort. Raw earth combined with biomass-derived materials is currently gaining strong attention today as they are low-environmental impact materials that also contribute significantly to improving the building hygrothermal performance and comfort. This study aims to develop new raw earth/hemp composites with low hemp shiv content to improve their hygrothermal properties when used as sustainable building materials. The hygrothermal properties of raw earth composites were analyzed including moisture buffer value, water vapor permeability, moisture sorption isotherms, and thermal conductivity. The mechanical properties were also investigated. The moisture buffer capacity result is increased with the hemp shiv content and it exhibits an “excellent” category, from 2.65 g/(m2

While passive radiative cooling effectively mitigates summer cooling loads, its static spectral properties often cause a winter heating penalty. Passive temperature-adaptive materials (TAMs) resolve this mismatch through autonomous, zero-energy spectral regulation. Focusing on opaque building envelopes, this review systematically categorizes TAMs based on their structural mechanisms and statistically evaluates the optical performance of each category. Building on these performance insights, we trace the technological evolution from single-band modulation to ideal dual-band synergy, which maximizes summer heat rejection while enhancing winter solar gain and suppressing radiative loss. Crucially, recognizing the distinct operational physics of TAMs compared with static radiative cooling materials, we propose a specialized benchmarking framework to accurately evaluate their dynamic thermal performance. Beyond mechanisms, we critically evaluate engineering barriers for large-scale deployment, specifically weatherability, aesthetic integration, and eco-friendliness. Finally, we highlight the expansion of TAMs to greenhouses, vehicles, and smart textiles.

Flat skylights, as key transparent envelope elements, offer significant potential for achieving healthy indoor environments and building sustainability but face the thermal-daylighting conflict that hinders comfort and impacts building energy consumption. This review synthesizes evaluation systems, innovative technologies, core conflicts, and development trends in optimizing the thermal-daylighting performance and energy efficiency of flat skylights. Key findings highlight the innovative advancements in multi-objective optimization (MOO) technologies and advanced skylight materials. However, the limitations, including the isolation of thermal and daylighting comfort, along with deficiencies in static evaluation models and human-centered integration, still remain. The review further assesses the potential challenges in resolving the conflicts. Conclusively, it underscores the urgent need to enhance MOO algorithms, dynamic environmental adaptability, and human-centered feedback design for the study in flat skylights. The insights aim to promote the transformation of flat skylights from static design to dynamic intelligent control for healthier and more sustainable buildings.

Given the escalating global energy crisis and environmental degradation, reducing energy consumption in office buildings, which account for 20-24 % of public building energy use, has become imperative for achieving carbon neutrality. Radiative cooling and photovoltaic (PV) materials integrated into building envelopes offer energysaving potential, yet existing studies neglect systematic comparisons of their synergies. This study combines EnergyPlus simulations and parametric analysis to evaluate radiative cooling films, PV films, cool coatings, and PV panels in a Nanjing office building across five Chinese climate zones. Key findings reveal that PV films achieve a maximum temperature reduction of 0.5 degrees C in south-facing rooms during summer but increase winter heating demands, with top-floor rooms experiencing a 3.4 degrees C temperature drop. Cool coatings reduce summer indoor temperatures by 1.4 degrees C yet induce winter overcooling, while wall-mounted PV panels show negligible thermal impacts. Radiative cooling films balance glare control with daylight sufficiency, maintaining a Daylight Glare Probability below 0.35, whereas PV films necessitate artificial lighting due to low transmittance. Regionally, radiative cooling achieves cooling savings of 79.29 MWh in hot Guangzhou but increases heating loads by 27.5 MWh in cold Harbin. This work pioneers a holistic thermo-optical-energy performance framework, guiding climate-resilient building envelope designs.

Alternative drag approaches for representing unresolved buildings were proposed in literature for computational fluid dynamics (CFD) simulation of macroscopic urban airflow. As a contribution, the present work derives the volumetric drag coefficient (C & lowast;d) through canopy drag and velocity analysis and provides appropriate correlations for C & lowast; d against urban morphological parameters. A total of 72 cases across various urban configurations are investigated, categorized by building typology, horizontal layout, height variability, and plan area density (7p, from 0.0625 to 0.57). Reynolds-Averaged Navier-Stokes (RANS) simulations with periodic boundary conditions are performed to model fully developed flows. Results for the normalized drag force and superficial velocity and their relations with 7p are evaluated. Subsequent evaluation of the profiles for the sectional coefficients (C & lowast;d(Z)) reveals four distinct types with variations in uniform-height cases and combinations in varying-height cases. A throughout correlations analysis, facilitated by data transformation, identifies the straightforward relations between C & lowast; d and frontal area density (7f) and tortuosity (z). The followed stepwise regression provides a recommended formula for C & lowast; d , demonstrating a proper fit with the simulated values. These findings facilitate the understanding and appropriate estimation of C & lowast; d and C & lowast; d ( Z ), promoting the application of macroscopic turbulence models, for neighborhood-scale wind and air quality studies.

Spatially-averaged wind profiles over the neighbourhood scale are commonly characterized in the literature as exhibiting exponential or logarithmic shapes. Further evaluation of in-canopy averaged velocity and its components-the main aim of this work-can contribute to a more comprehensive characterization of canopy wind conditions. The conventional computational fluid dynamics approach, modelling buildings by fully resolved method (FRM), is taken as the basis to evaluate the drag-based approaches: the porous media model (PMM) and the velocity reconstruction method (VRM). The VRM is particularly proposed as an engineering solution, implemented in Python, that uses drag-velocity functions to inversely calculate the averaged velocities in target neighbourhoods. Both fully-developed flows and flow adjustments through generic neighbourhoods within simplified districts under parallel and oblique inflows are investigated. The neighbourhoods feature moderate size, uniform height, regular and staggered arrangements, and varying plan area density (lambda p, from 0.07 to 0.40). Results reveal that the normalized volumetric drag coefficient (C & lowast;d) varies for the same neighbourhood under different flow conditions, e.g., with a median reduction of up to 20 % for regular-medium cases. The comparison demonstrates the PMM's ability to replicate wind profiles, despite with overestimation for windward neighbourhoods. The qualitative and statistical analyses (via R2 and RMSE) confirm that VRM predicts reasonable averaged velocity components, though it tends to slightly overestimate due to neglecting turbulence processes. Drag correlations, fitted in trigonometric Fourier series against wind direction, provide a lightweight program for estimating neighbourhood-averaged velocities, showing promise for integration into urban building energy modelling tools.

Integration of solar chimney is an effective passive strategy for facilitating fresh air flow and offering significant potential for building energy conservation. This research evaluates the optimal design and control strategy for a six-story office building that includes a solar chimney, focusing on stack effect ventilation and energy performance throughout the year. The ventilation rates in different configurations of solar chimney are compared to meet fresh air requirements. The results indicate that the separated solar chimney ensures uniform airflow across each floor, with ventilation standard-reaching rates ranging from 79.5% to 88.6%. Furthermore, maximums of air flow rate occur at each floor, with critical cavity width values of 0.5 m, 0.4 m, 0.4 m, 0.3 m, 0.3 m, and 0.2 m on 1st to 6th floor, respectively. Under the condition of equal cavity inlet area, air flow rates rise with the increasing length/width ratios. Finally, when the outdoor temperatures fall beyond the design range, controlling excessive ventilation generated by solar chimney leads to a 19.6% reduction in total energy consumption over the year, with 71.5% of the savings during winter.

Building surfaces are highly heterogeneous and exhibit important impacts on the urban microclimate. This study examines the impact of window-to-wall ratio (WWR) on the thermal environment of street canyons through scaled outdoor experiments. Three street canyons with WWRs of 0 %, 25 %, and 50 % were studied to assess the WWR effects on fa & ccedil;ade surface, indoor, outdoor air, and ground temperatures. The results reveal an apparent time-dependent impact of WWR on both fa & ccedil;ade and air temperatures within the street canyon. Specifically, increasing the WWR led to higher morning temperatures of fa & ccedil;ades but reduced afternoon temperatures, with a maximum decrease of 7.28 degrees C observed on the east fa & ccedil;ade. Higher WWRs lowered west indoor temperatures by up to 6.38 degrees C but increased east indoor temperatures by 5.32 degrees C. In the street canyon, air temperatures decreased by an average of 0.7 degrees C, and ground surface temperatures exhibited the most significant reductions during nighttime. Overall, WWR increases produced a daily net cooling effect ranging from 0.3 degrees C to 1.8 degrees C, with the cooling generally becoming more pronounced at higher WWRs, except for the increase of east indoor temperatures. These findings underscore the complex influence of heterogeneous wall material properties on the urban thermal environment. The experimental data obtained in this study provide useful experimental data for computational fluid dynamics (CFD) simulation validation and shed some light on improving urban canopy parameterization by considering the window effect.

The functional and health-related impacts in the built environment of electric lighting are receiving increasing attention, with its design and evaluation heavily relying on the accuracy and applicability of simulation tools. DIALux evo and Ladybug+Honeybee (L + H), as dominant lighting simulation tools, adopt different principles in lighting research and practice. However, their performance characteristics and application fields remain unclear. The review analyzes the working performance of DIALux evo and L + H across three dimensions: modeling capability, lighting data and luminaire arrangement, and lighting calculation. Additionally, it examines their applications across different countries and research fields. DIALux evo, equipped with a built-in luminaire database and standardized workflow, demonstrates high efficacy in static lighting validation scenarios. However, limitations in curved surface modeling and high computational demands constrain its applicability in complex spaces. In contrast, L + H leverages the parametric advantages of the Rhinoceros and Grasshopper platform, enabling dynamic lighting simulations and multi-objective optimization. Nonetheless, challenges exist in interdisciplinary research due to its lack of a built-in luminaire database and operational complexity. Based on these findings, future optimization directions are proposed: DIALux evo should enhance AI-driven intelligent lighting arrangement algorithms and integrate multi-physics coupling functionalities, while L + H should establish a standardized luminaire database. Furthermore, the integration of algorithms and technological frameworks is recommended to facilitate the transition of these tools from design-oriented software to comprehensive research platforms. The review provides a theoretical foundation for the selection and development of electric lighting simulation tools, contributing to methodological innovations for healthy lighting environments.

The Spring Festival, a cornerstone of Chinese cultural heritage, fosters family reunions. However, its traditional practices, such as burning incense and setting off fireworks, generate severe air pollution and pose significant health threats. This presents a critical dilemma regarding how rural residents balance the imperatives of cultural preservation against environmental health risks. This study investigates this trade-off using a multidisciplinary approach. Field measurements within a rural household during the 2024 festival revealed alarmingly high indoor PM2.5 levels, peaking above 1000 μg/m3 on New Year's Eve and averaging over 600 μg/m3. Furthermore, a survey of 1035 residents across nine northern provinces found that 38.7% and 19.7% reported adverse physiological symptoms from high outdoor and indoor pollutant levels, respectively. Notably, of those experiencing symptoms, an overwhelming 81.8% were still willing to tolerate temporary air pollution for cultural fulfillment derived from the festival. This underscores that for these rural residents, the perceived value of traditional observance can outweigh immediate environmental health concerns. Therefore, policymakers must develop strategies that reconcile public health and cultural heritage. Effective interventions could include promoting eco-friendly fireworks, organizing pollution-free community events, and subsidizing advanced ventilation technologies.