Seasonal effects of urban street shading on long-term outdoor thermal comfort

As shading, an important factor in urban environments, affects thermal environments and long-term thermal comfort, this study conducted several field experiments to analyze the outdoor thermal conditions on urban streets in central Taiwan. The RayMan model was utilized for predicting long-term thermal comfort using meteorological data for a 10-year period. Analytical results indicate that slightly shaded areas typically have highly frequent hot conditions during summer, particularly at noon. However, highly shaded locations generally have a low physiologically equivalent temperature (PET) during winter. Correlation analysis reveals that thermal comfort is best when a location is shaded during spring, summer, and autumn. During winter, low-shade conditions may contribute to the increase in solar radiation; thus, thermal comfort is improved when a location has little shade in winter. We suggest that a certain shading level is best for urban streets, and trees or shade devices should be used to improve the original thermal environment.     

Residential air exchange rates in three major US metropolitan areas: results from the Relationship Among Indoor, Outdoor, and Personal Air Study 1999–2001

Abstract We report approximately 500 indoor–outdoor air exchange rate (AER) calculations based on measurements conducted in residences in three US metropolitan areas in 1999–2001: Elizabeth, New Jersey; Houston, Texas; and Los Angeles County, California. Overall, a median AER across these urban areas and seasons was 0.71 air changes per hour (ACH, or per hour; n = 509) while median AERs measured in California (n = 182), New Jersey (n = 163), and Texas (n = 164) were 0.87, 0.88, and 0.47 ACH, respectively. In Texas, the measured AERs were lower in the summer cooling season (median = 0.37 ACH) than in the winter heating season (median = 0.63 ACH), likely because of the reported use of room air conditioners as Houston is typically hot and humid during the summer. The measured AERs in California were higher in summer (median = 1.13 ACH) than in winter (median = 0.61 ACH). Because the summer cooling season in Los Angeles County is less humid than in New Jersey or Texas, natural ventilation through open windows and screened doors likely increased measured AER in California study homes. In New Jersey, AER were similar across heating and cooling seasons, although the median AER was relatively lower during the spring.

Practical Implications

Adequate ventilation or air exchange rate (AER) for an indoor environment is important for human health and comfort, and relevant to building design and energy conservation and efficiency considerations. However, residential AER data, especially measured by more accurate non‐toxic tracer gas methodologies, are at present quite limited worldwide, and are insufficient to represent the variations across regions and seasons within and between homes, including apartments and condominiums in more densely populated urban areas. The present paper presents quantitative and qualitative data to characterize residential AERs in three US urban areas with different climate attributes.     

基于风热环境的开敞空间周边建筑围合研究

城市形态与环境舒适性的关系是城市设计的热门议题。探讨风热环境参数与街区围合度的关系及开敞空间周边建筑的围合形式，目的在于为空间形态控制提供思考路径。选取武汉市的开敞空间共68处作为研究对象，在此基础上抽象出具有代表性的街区理想空间模型，运用Phoenics软件量化模拟冬夏两季典型日的典型时刻不同围合度下室外环境空气速度、温度和空气压力值，并进行相关性分析。结果显示，城市集中建设区开敞空间周边建筑围合度与夏季空气速度呈负相关关系。最后根据风环境对人体影响的分析结果对开敞空间提出相应的城市设计建议。     

Shading effect on long-term outdoor thermal comfort

Shading affects outdoor thermal environments and, therefore, influences the thermal perceptions of people in outdoor spaces. Since most field studies examining outdoor thermal comfort merely elucidated characteristics measured on a particular day, these studies may not represent annual thermal conditions accurately. Therefore, this study conducted 12 field experiments to analyze outdoor thermal conditions on a university campus in central Taiwan, and utilized RayMan model for predicting long-term thermal comfort applying meteorological data for a 10-year period. The physiologically equivalent temperature (PET) is employed as a thermal index. The thermal comfort range of Taiwanese residents obtained in a previous survey was applied as the criterion for determining whether a thermal environment is comfortable or uncomfortable. Analytical results indicate that the sky view factor (SVF), which represents the percentage of free sky at specific locations, significantly affects outdoor thermal environments. Analytical results indicate that a high SVF (barely shaded) causes discomfort in summer and a low SVF (highly shaded) causes discomfort in winter. As Taiwan has hot summers and mild winters, sufficient shading should be provided by trees and buildings to improve thermal comfort in summer. However, since the Taiwanese have poor tolerance of cold temperature, outdoor space planning should avoid creating areas with excessive shading. Therefore, the thermal requirements of residents and characteristics of the local climate and environment must be considered when creating shaded outdoor areas.     

Influence of urban geometry on outdoor thermal comfort in a hot dry climate: A study in Fez,Morocco

There are few studies on the microclimate and human comfort of urban areas in hot dry climates. This study investigates the influence of urban geometry on outdoor thermal comfort by comparing an extremely deep and a shallow street canyon in Fez, Morocco. Continuous measurements during the hot summer and cool winter seasons show that, by day, the deep canyon was considerably cooler than the shallow one. In summer, the maximum difference was on average 6 K and as great as 10 K during the hottest days. Assessment of thermal comfort using the PET index suggests that, in summer, the deep canyon is fairly comfortable whereas the shallow is extremely uncomfortable. However, during winter, the shallow canyon is the more comfortable as solar access is possible. The results indicate that, in hot dry climates a compact urban design with very deep canyons is preferable. However, if there is a cold season as in Fez, the urban design should include some wider streets or open spaces or both to provide solar access.     

Justice as a principle for the distribution of open space maintenance: the conceptions of housing staff and tenants

This paper is about what people conceive as just principles for the distribution of open space maintenance. Housing staff and residents’ conceptions of just distribution of open space maintenance were studied in rental housing areas with large green open spaces in Sweden. Qualitative interviews with nine housing staff members and 27 tenants in three multi-family housing areas owned and managed by different municipal housing companies revealed widely varying conceptions. These could be partly classified into three basic principles: equal outcome, same inputs and less inputs (when decline is high). The conceptions varied among interviewees with different roles in providing upkeep, suggesting that they partly depended on the individual’s insight into the services. These personal conceptions of justice influence how people experience service distribution in a neighbourhood and pose a challenge for actors dealing with strategic decisions on open space maintenance.     

Assessment of the microclimatic and human comfort conditions in a complex urban environment: Modelling and measurements

Several complex thermal indices (e.g. Predicted Mean Vote and Physiological Equivalent Temperature) were developed in the last decades to describe and quantify the thermal environment of humans and the energy fluxes between body and environment. Compared to open spaces/landscapes the complex surface structure of urban areas creates an environment with special microclimatic characteristics, which have a dominant effect on the energy balance of the human body. In this study, outdoor thermal comfort conditions are examined through two field-surveys in Szeged, a South-Hungarian city (population 160,000). The intensity of radiation fluxes is dependent on several factors, such as surface structure and housing density. Since our sample area is located in a heavily built-up city centre, radiation fluxes are mainly influenced by narrow streets and several 20–30-year-old (20–30 m tall) trees. Special emphasis is given to the human-biometeorological assessment of the microclimate of complex urban environments through the application of the thermal index PET. The analysis is carried out by the utilization of the RayMan model. Firstly, bioclimatic conditions of sites located close to each other but shaded differently by buildings and plants are compared. The results show that differences in the PET index amongst these places can be as high as 15–20 ^°C${}^{°}\mathrm{C}$ due to the different irradiation. Secondly, the investigation of different modelled environments by RayMan (only buildings, buildings+trees$\mathrm{buildings}+\mathrm{trees}$ and only trees) shows significant alterations in the human comfort sensation between the situations.     

Physical characterization of particulate matter and ambient meteorological parameters at different indoor–outdoor locations in Singapore

The paper reviews the exposure to fine and coarse particles in different indoor and outdoor locations. The methodology involves measuring the particulate matter at different indoor and outdoor locations. The locations included a major expressway (high traffic volume), a minor road, and naturally and mechanically ventilated indoor spaces. It was observed that significant concentrations of fine particles were found at the expressway as compared to the normal road and naturally ventilated space. However, larger size particles were found to be higher in number density (count per litre) and mass concentration at the minor road and naturally ventilated space at close proximity to the minor road. In the mechanically ventilated space the particles above 1 μm size were negligible both in count and mass. A linear relation was established between the particle mass (PM₁₀) and particle count (r²=0.5564$r^2=0.5564$, n=60$n=60$). Denser particulate matter was found at naturally ventilated indoor spaces in the evenings. Indoor–outdoor ratio (I/O) for the naturally ventilated space is observed to be closer to unity as in the case of mechanically ventilated space with 0.46. A higher I/O ratio is observed in the evening as compared to morning for the naturally ventilated space. Better correlation was observed between fine and coarse mode particles at the expressway as compared to the minor road.     

Indoor thermal environment and energy saving for urban residential buildings in China

The purpose of this survey is to investigate the actual conditions of the residential indoor thermal environment in urban areas in China for evaluating thermal comfort and predicting the energy conservation feasibility for space heating and cooling.The apartment homes under investigation were located in the urban areas of nine major cities. The questionnaire survey revealed building characteristics, the types of space heating and cooling system in use, aspects of life style, during winter and summer seasons, and so on. The measurement showed that winter indoor temperatures in Harbin, Urumqi, Beijing and Xi’an remain at a relatively stable level near 20 °C due to the central heating system installed. However in the other cities lacking central heating systems, indoor temperatures fluctuated as a function of the change of outdoor temperature. On the other hand, summer indoor evening temperatures in Shanghai, Changsha, Chongqing and Hong Kong were higher than the comfort zone of ASHRAE. Therefore it is expected that energy use for space heating and cooling in the southern China will increase in the near future because of occupants’ requirement for comfortable indoor environment. Based on the results yielded by this study, in Beijing the calculation of space heating and cooling loads indicated that the energy used to heat indoor spaces can be halved by installing thermal insulation and properly sealing the building.     

我国夏热冬冷地区的城市绿地设计初探

本文初步探讨了我国夏热冬冷地区的城市绿地设计。针对夏热冬冷地区的特殊气候特征,从城市绿地的选址、夏季通风、冬季防风、夏季遮阴、冬季日照、植物配置等方面展开较为深入的研究。并对于此类气候地区的城市绿地设计给出了一些设计建议。     

半干旱区城市广场树木形态对微气候的影响研究

植物群落是改善微气候的重要影响因素,是微气候变化的驱动力之一,它对微气候的形成、变化等进程的影响已成为当前研究的重要组成部分。以半干旱区城市呼和浩特成吉思汗广场中4种不同植物群落类型的样地和1块空地为试验地,进行风速、温度、湿度实测和ENVI-met软件模拟分析,以评估各样地对微气候的影响。研究结果表明:植物群落调节微气候具有明显的季节性差异,且与树木胸径、高度、郁闭度、叶面积指数有明显相关性;乔木高度、形状、胸径可直接影响微气候环境,25 m高、心形、中等胸径的落叶乔木在夏季的降温、增湿、通风作用最明显;5m高、圆柱形、小胸径的落叶乔木在春、秋、冬3季增温、增湿、降风效果最优。揭示了广场植物群落数量属性与微气候变量之间的联系,确定了关键微气候变量在各植物群落中的变化规律,此结果可为半干旱地区广场绿色空间的植物种植设计提供参考及依据。     

Profiles and seasonal distribution of airborne fungi in indoor and outdoor environments at a French hospital

A one-year prospective survey of fungal air contamination was conducted in outdoor air and inside two haematological units of a French hospital. Air was sampled with a portable Air System Impactor. During this period of survey, the mean viable fungal load was 122.1 cfu/m³ in outdoor air samples, and 4.1 and 3.9 cfu/m³ in samples from adult and pediatric haematology units, respectively. In outdoor samples, Cladosporium was the dominant genus (55%) while in the clinical units, Penicillium sp. (23 to 25%), Aspergillus sp. (15 to 23%) and Bjerkandera adusta (11 to 13%) were the most frequently recovered airborne fungi. The outdoor fungal load was far higher in autumn (168 cfu/m³), spring (110 cfu/m³) and summer (138 cfu/m³) than in winter (49 cfu/m³). In indoor air, fungal concentrations were significantly lower in winter (2.7 to 3.1 cfu/m³) than in summer (4.2 to 5.0 cfu/m³) in both haematology units. In the outdoor environment, Penicillium sp. and Aspergillus sp. were more abundant in winter while the levels of Cladosporium were lowest during this season. In the haematological units, the presence of Aspergillus sp. was stable during the year (close to 20%), Bjerkandera sp. was particularly abundant in winter (close to 30%); levels of Penicillium sp. were highest in autumn while levels of Cladosporium sp. were highest in spring and summer.     

The use of polar organic compounds to estimate the contribution of domestic solid fuel combustion and biogenic sources to ambient levels of organic carbon and PM2.5 in Cork Harbour, Ireland

PM_2.5 samples collected at Cork Harbour, Ireland during summer, autumn, late autumn and winter, 2008-2009 were analyzed for polar organic compounds that are useful markers for aerosol source characterization. The determined compounds include tracers for biomass burning primary particles, fungal spores, markers for secondary organic aerosol (SOA) from isoprene, α-/β-pinene, and d-limonene. Seasonal and temporal variations and other characteristic features of the detected tracers are discussed in terms of aerosol sources and processes. The biogenic species were detected only during the summer period where the contributions of isoprene SOA and fungal spores to the PM_2.5 organic carbon (OC) were estimated to be 1.6% and 1% respectively. The biomass burning markers, and in particular levoglucosan, were present in all samples and attributed to the combustion of cellulose-containing fuels including wood, peat, bituminous and smokeless coal. The contribution of domestic solid fuel (DSF) burning to the measured OC mass concentration was estimated at 10.8, 50, 66.4 and 74.9% for summer, autumn, late autumn and winter periods, respectively, based on factors derived from a series of burning experiments on locally available fuels. Application of an alternative approach, namely principal component analysis-multiple linear regression (PCA-MLR), to the measured concentrations of the polar organic marker compounds used in conjunction with real-time air quality data provided similar trends and estimates for DSF combustion during all seasons except summer. This study clearly demonstrates that, despite the ban on the sale of bituminous coal in Cork and other large urban areas in Ireland, DSF combustion is still the major source of OC during autumn and winter periods and also makes a significant contribution to PM_2.5 levels. The developed marker approach for estimating the contribution of DSF combustion to ambient OC concentrations can, in principle, also be applied to other locations.     

船舶围壁空气层自然对流对传热系数的影响分析

本文采用数值模拟软件对不同室内外温度条件下的船舶水平及垂直围壁稳态传热进行模拟计算。结果表明水平围壁在冬季和夏季的传热系数存在明显的差异,而且冬季的传热系数要比夏季的传热系数大的多,这主要是水平空气层在冬季的自然对流比夏季的自然对流强烈。垂直围壁冬季和夏季传热系数的差异很小。结果也表明同一季节的室内外温差的变化对围壁传热系数的影响均很小。因此在计算船舶空调负荷时,水平围壁传热系数取值应对冬季和夏季予以区分而垂直围壁的传热系数选取不需区分冬季和夏季。     

The rooftop shading system of the Humanities Building at SCUT

Rooftop shading is an effective green building design strategy in subtropical areas; it can create an ecological rooftop space and produce energy savings for rooms on the top floor. This article describes the rooftop shading system of the Humanities Building at SCUT (South China University of Technology). A shading calculation software developed by the Building Energy Efficiency Laboratory (BEEL) of SCUT is used to calculate and analyze the rooftop shading effect in summer and winter. The actual performance of this rooftop shading system was evaluated by measuring the wet bulb globe temperature (WBGT) in the shaded and unshaded areas under the shading system on July 2, 2003.     

Interaction between the mixing and displacement modes in a naturally ventilated enclosure

Experiments are carried out to study for the first time interactive phenomena in buoyancy-induced natural ventilation in a full-scale enclosure with upper and lower openings on one of the sidewalls. The interaction between the mixing and the displacement ventilation modes is revealed by opening the lower vent to different heights while the upper vent is kept fully open. Both the transient process and steady state interaction are explored. Measurements include temperature differences between inside and outside and air velocity through the upper opening. The level of the neutral plane at the upper vent, defined here as the plane separating between inflow and outflow, decreases with R^*$R^{*}$, the ratio between the opening heights (and areas) of the lower and upper vents. Experiments show that when 0*<0.27$0<R^{*}<0.27$ the mixing and displacement modes interact through a new combined ventilation mode. For 0.53*?1$0.53<R^{*}?1$, the displacement mode dominates whereas in the intermediate range, 0.27?R^*?0.53$0.27?R^{*}?0.53$, either the combined or the pure displacement mode takes place. The experiments are in qualitative agreement with a previous theoretical model.     

A field study on determination of preferences for windows in office environments

We aimed to determine the preferences for windows in office spaces and discover the underlying reasons which may affect design decisions. We conducted a field study on office buildings in Izmir–Turkiye. The research findings indicated that majority of users (48.6%; n=107$n=107$) have preferred firstly window-wall, which has the largest window area, secondly horizontal window (35%; n=77$n=77$) and thirdly square window types (10.9%; n=24$n=24$) for their own workspaces. Although having equal surface areas in the preference scale, square-shaped windows have been preferred much more than the rectangular and round shaped ones and horizontal shaped windows than the vertical ones. The window type, gender, quality of office job and quality of view created significant differences in determining prior factors behind window preferences.     

Field experiments on natural energy utilization in a residential house with a double skin façade system

Energy consumption in the residential and commercial sector accounts for over 25% of the total in Japan. With the information technology revolution and the improving requirement for indoor air environment, energy consumption for household air conditioning is increasing. In this research, a double skin facade is proposed for a two-story house in Kitakyushu of Japan. The stack effect in the double skin space during the summer, the green house effect during the winter and the availability for free air-conditioning during the autumn have been studied. The temperature distribution, thermal performance in the double skin space and its impact on air-conditioning load in rooms have been measured. Results show that the double skin façade leads to about 10–15% energy saving for cooling in the peak of summer because of heat exhausted by natural ventilation, 20–30% energy for heating in winter because of the green house effect, and the temperature adjustment is quite large with the different operation mode of the double skin system during the intermediate seasons. Therefore the double skin system is proved to be effective in energy conservation in residential buildings.     

Glazed spaces in Nordic climates

A semi-climatized zone in the shape of a glazed space is heated to some degree by solar radiation and to some degree by excess heat or heat loss from the main and fully insulated part of the building. Such a space will not offer full thermal comfort for permanent occupancy during the winter season, but it is useful for secondary functions such as circulation, storage, physical activities, etc. During the summer season glazed spaces will also be very attractive for ordinary occupancy.

A condition for energy conservation is that these spaces are not heated directly but utilize heat loss and possibly excess heat from the adjoining buildings. If they are properly positioned and constructed, they will also function as solar collectors.

The energy reduction potential will vary greatly with the relative size of the spaces, with the system installed, and with possibilities for long term storage. If the glazed space covers relatively large parts of the adjoining buildings, the reduced heat loss from these may be considerable. If in addition a certain minimum temperature can be kept in the glazed space, the need for heating in the adjoining buildings may be minimal.

Abroad such spaces are often used consciously as architectural elements due to their special spatial character. In countries like Norway they may in addition serve several needs resulting from the special climatic conditions.

SINTEF has developed energy conservation systems based on this concept and has tested them in experimental buildings. One example is the three solar energy houses in the Heimdal low energy dwellings project which totals 14 houses. Another example is a day care centre now under development for the local student union.     

Seasonal variations in the household exposures of Korean housewives to volatile tap water disinfection by-products

This study was conducted to compare housewives' winter and summer exposures to volatile disinfection by-products (DBPs) in chlorinated tap water. A total of 60 households were visited for this purpose: 27 in winter and 33 in summer. Each subject was given a questionnaire regarding general tap water use, household ventilation time, and activities related to water use. Tap water, household air, and exhaled breath samples were also collected during the visits. All of the subjects answered that they consumed tap water after either thermal treatment or purification through filtration systems. A longer ventilation time in winter than in summer resulted in a higher inhalation exposure for housewives during that season. Estimated chronic daily intakes calculated for winter and summer showed that in winter, the greatest risk at home is inhalation exposure while resting at home, whereas in summer, it is showering. In both seasons, the ingestion route can be discounted, because tap water is processed before consumption, eliminating the volatile DBPs. From this study, it is evident that the inhalation of household air while resting at home cannot be ignored in risk assessment. Moreover, the fact that water is normally boiled or filtered before use should also be considered.