Outdoor Comfort Research Articles

Noise-reducing vents for windows in warm, humid, tropical countries

ABSTRACTSustainable building design requires the application of natural ventilation, which has three prerequisites – a comfortable outdoor air temperature (20–25°C), unpolluted outdoor air and a low-noise environment (under 55 dBA). There are many locations where the first two prerequisites are met, but the environmental noise makes applying natural ventilation challenging. This research developed an auxiliary noise-reducing vent for windows (NRVW) that allows daylight and outdoor air to enter the room while reducing the penetration of outdoor noise. As an auxiliary, the NRVW is intended to be integrated into any (double) glazed windows with a sound transmission class (STC) above 25 dBA. The research used physical model experiments to measure the NRVW’s STC and outdoor–indoor transmission class (OITC). Digital model simulation was used to measure the NRVW’s ventilation performance. It was found that NRVW has a rating of STC 18 and OITC 16, and it generates indoor air velocity of 0.015–0.086 m/s in the occupants’ zone for an outdoor wind speed of 1–5 m/s. Modification of the room interior increases the indoor air velocity to 0.147 m/s. Computer simulation also demonstrated that, with an occupant inside the room, an outdoor air temperature of 25°C and outdoor wind speed of 1–5 m/s maintained the indoor air temperature at 25.309–25.258°C, indicating that the resulting airflow could keep the indoor air temperature low. Although the NRVW was originally developed for warm–humid climate conditions, it is also applicable for other climates if the required outdoor conditions are met.

Association between human and animal thermal comfort indices and physiological heat stress indicators in dairy calves

Warm summer episodes have a significant effect on the overall health and well-being of young cattle; however, it is not known which temperature measure should be used for estimating heat stress in dairy calves. In this study, generalized linear mixed-effects models were used to estimate the relationships between thermal comfort indices and animal-based heat stress indicators in sixteen Holstein bull calves that were housed in individual calf hutches. Data were collected under continental weather characteristics over a 5-day period: day 1 (lower-temperature day), days 2 and 3 (heat stress days), and a 2-day post-stress period. Relative humidity, ambient temperature, the heat index, the humidex and five different temperature–humidity indices (THI) were used as thermal indices. Physiological variables monitored included respiratory rate, rectal temperature, ear skin temperature and heart rate. The heat index and the humidex measuring human thermal comfort were more closely associated with physiological measures than were the ambient temperature or the THIs (in case of heat index: R2 = 0.87 for respiratory rate, R2 = 0.63 for rectal temperature, R2 = 0.70 for ear skin temperature, and R2 = 0.78 for heart rate, respectively; in case of humidex: R2 = 0.85 for respiratory rate, R2 = 0.60 for rectal temperature, R2 = 0.68 for ear skin temperature, and R2 = 0.75 for heart rate, respectively). Based on our results, parameters of human outdoor comfort seem better to estimate heat stress in dairy calves in a continental region than those of THIs or ambient temperature.

How outdoor microclimate mitigation affects building thermal-energy performance: A new design-stage method for energy saving in residential near-zero energy settlements in Italy

Abstract Key research effort was dedicated toward zero-energy buildings. Recent interest is switching from single-building to inter-building scale, to enhance the whole district economic-environmental sustainability. This upscaling opens the doors to further optimization strategies thanks to outdoor microclimate mitigation aimed at reducing winter thermal losses and summer overheating. This work proposes a novel design-stage replicable method for multiscale microclimate improvement correlated to building thermal-energy analysis in a residential near-zero-energy district in central Italy. Cool surface installation and conscious greenery design in the outdoors were used in the district of single-family houses. Therefore, a microclimate simulation was performed to elaborate realistic weather files to be used in the second-stage dynamic thermal-energy simulation at building level, in order to evaluate the impact of the local microclimate on building thermal-energy performance and renewables’ production. Microclimate analysis demonstrated how local conditions affect outdoor comfort and that they may be considered in the same way as traditional energy-efficiency improvement early-stage design strategies at building scale, being able to reduce building energy need for HVAC up to 10% in the studied conditions. Therefore, new potentialities of inter-building scale analyses for energy efficiency enhancement and renewable energy exploitation are expected while downscaling microclimate assessment toward building thermal-energy performance.

Facing the urban overheating: Recent developments. Mitigation potential and sensitivity of the main technologies

Urban overheating represents an internationally acknowledged anthropogenic phenomenon related to climate change and to the massive shift of population worldwide toward urban areas, which are increasingly enlarging their size and density. The consequences of this urban warming (i.e., urban heat island) may compromise citizens’ quality of life in urban areas, indoor and outdoor comfort perception, and building energy performance in summer conditions. In this panorama, this review presents recent contributions demonstrating the effectiveness and urgent need of existing mitigation strategies. The same strategies are also comparatively assessed by means of a sensitivity analysis demonstrating their effect with varying climate conditions and urban context. Results of existing studies, validated by the present assessment, aimed at quantitatively investigating the effect of mitigation strategies for reducing building cooling needs and enhancing urban well‐being, thanks to international scientific effort carried out in the last decades. To this aim, the logical flow of the review deals with the main technologies for urban warming mitigation are described, together with the main findings of numerical and experimental research initiatives, demonstrating the field effect of improving pedestrians comfort and urban well‐being all around the world. Then, the mitigation potential of key green, water and cool strategies is critically reviewed, and further scientific and implementation needs are discussed. All the reviewed contributions demonstrate an undeniable technology readiness level for their practical implementation and highlight the true necessity of a shared and synergistic policy effort worldwide.This article is categorized under: Energy and Urban Design > Systems and Infrastructure Concentrating Solar Power > Climate and Environment Energy Efficiency > Climate and Environment

Outdoor comfort conditions in urban areas: On citizens’ perspective about microclimate mitigation of urban transit areas

Understanding citizen environmental perception is a crucial issue to improve outdoor environmental and landscape quality. This paper is aimed at investigating the perspective of travelling citizens about local microclimate conditions in a transportation open-air hub of an urban district in central Italy, to propose effective mitigation strategies. Therefore, a survey was submitted to pedestrians while crossing the area to understand their actual perception of visual-thermal-acoustic conditions characterizing the outdoor environment, with varying weather and personal characteristics. Simultaneously, the continuous in-situ monitoring of the main environmental parameters was performed. Finally, the benefits generated by selected microclimate mitigation and landscape improvement strategies were quantitatively assessed by means of validated microclimate district models. Results of the field survey highlighted the minor tolerance of the local environment by local citizens compared to tourists, especially those coming from denser and more polluted cities. Moreover, the simulations confirmed the capability of selected microclimate mitigation strategies against anthropogenic heat, to improve pedestrians’ outdoor thermal comfort conditions in summer, without winter penalties. In particular, the vegetation increase, according to pedestrians’ request for additional green areas, combined to other solutions for sustainable landscape change, showed the most significant impact in summer overheating mitigation and urban resilience to anthropogenic climate change.

Public Open Space Design Study on the Basis of Microclimate and Spatial Behavior in Hot and Cold Weather Conditions in Downtown Area

Microclimate in open space affected by the urban layouts and spatial forms plays an important role in the outdoor comfort, thus the outdoor activities based on the comfort sensation will directly affected by the microclimate. An outstanding open space should satisfy different requirements of outdoor activities and create relatively comfortable sensation.Most studies have been conducted on these relationships only above 0 Celsius degree. However, only few have focused on extreme situations in both hot and cold seasons. Therefore, from microclimate perspective, taking people’s comfort and spatial behaviors as criterions, this research discussed how the open space forms affect microclimate, thus affect comfort sensation and spatial behaviors. The outcomes may provide some useful insights for planners and architects to understand the relationship among microclimate, open space and people.Results showed that microclimate obviously affected people’s comfort. In hot season, shade and air-flow played crucial roles in outdoor comfort. People tend to stay outside in the shade and the area with higher air velocity. After sunset is popular period for outdoor activities. In cold season, at the same ambient temperature, lower air velocity raised the comfort level. Shade also had influences on comfort sensation but do not affect spatial behaviors significantly.This paper also proposes optimization design proposals of densely populated open space based on extreme microclimate and spatial behaviour.

Outdoor thermal comfort and behaviour in urban area

Outdoor comfort is important due to the public spaces functions. Open spaces provide thermal comfort and a pleasant experience to improve the city life quality effectively. The influence of thermal comfort in outdoor activities is a complex problem. This paper presents a literature review and discussion of aspects of physical, psychology, and social behaviour toward outdoor thermal comfort. The valuation is determined not only by the “physical state” but also by the “state of mind”. The assessment is static and objective (i.e., physical and physiological characteristics) that it should be measured. Furthermore, an effective model to provide the knowledge of climatic conditions, as well as the dynamic and subjective aspects (i.e., psychological and social characteristics and behaviour), requires a comprehensive interview and observation. The model will be examined to describe the behaviour that is a reflection of perception and behaviour toward the environment. The adaptation process will constantly evolve so that it becomes a continuous cause between human behaviour and the spatial setting of the formation, which is eventually known as places and not just spaces. This evolutionary process is a civic art form.

The impact of the building envelope with the green living systems on the built environment

Altering the surface cover of an area causes the change in the environment. By erecting buildings change in the flow of energy and matter through the urban ecosystems occurs creating multiple environmental problems. Built areas exert considerable influence over their local climate, amplifying problems such as heat waves, air pollution, and flooding. Greening the building envelope these problems can be partially mitigated. By combining nature and built areas in their designs, architects and urban planners can respond to these serious human health and welfare issues and restore the environmental quality of dense urban areas. Green living systems are not the only solution for new designs. Retrofitting existing buildings by altering the buildings' surficial properties can reduce buildings' energy consumption in case of older buildings with poor existing insulation. Implementation of green living systems in the building envelope, greening horizontal surfaces with intensive and extensive green roofs or using vegetation in vertical greening systems for fa?ades, is a strategy that provides ecological, economic, and social benefits. This review paper presents collected evidence of effects and explores the important role that the green living systems can play in the dense urban areas. Benefits such as heat island amelioration, reduction of buildings energy consumption, air quality and indoor and outdoor comfort conditions improvement, stormwater management and improved water run-off quality, will be mainly considered.

Effects of Building Design Elements on Residential Thermal Environment

Residential thermal environment affects the life of residents in terms of their physical and mental health. Many studies have shown that building design elements affect the urban thermal environment. In this study, Nanjing City was used as the study area. A three-dimensional microclimate model was used to simulate and analyze the effects of four main factors, namely, building height, density, layout and green ratio, on thermal environment in residential areas. Results showed that 25% building density obtained a low average air temperature (ATa) and average predicted mean vote (APMV) during 24 h. Thus, a higher building height indicates a lower ATa and APMV and better outdoor comfort level. In addition, peripheral layout had the lowest ATa and APMV, followed by the determinant and point group layouts. The green ratio increased from 0% to 50% with a 10% step and the ATa and APMV decreased gradually. However, when the green ratio increased from 30% to 40%, ATa and APMV decreased most. The effects of building height, density and green ratio on the thermal environment in residential areas were interactive. The effects of building density, green ratio and layout on hourly air temperature and hourly predicted mean vote in daytime varied from these indicators during night time. How the four building design elements interact with thermal environment were probed from two aspects of air temperature and thermal comfort based on the validated ENVI-met, which is the element of novelty in this study. However, thermal comfort has rarely been considered in the past studies about urban outdoor thermal environment.

Complying with the demand of standardization in outdoor thermal comfort: a first approach to the Global Outdoor Comfort Index (GOCI)

Over the past ten years the number of studies regarding outdoor thermal comfort has been progressively increasing. However, the existing works are characterized by a certain variety of instruments and methods. An example can be found in the indexes and evaluation scales used to estimate thermal perception. This is why this paper proposes the Global Outdoor Comfort Index (GOCI), which is obtained thanks to the combination of the empirical relations provided by the existing literature. Its independent variables are: air temperature (according to the reported F test value it is the most significant influencing parameter in the new proposed index), mean radiant temperature, relative humidity, wind velocity, latitude, mean annual temperature, mean temperatures of the hottest and coldest months. The index performances were compared to those of the Predicted Mean Vote (PMV), the Physiological Equivalent Temperature (PET), the Mediterranean Outdoor Comfort Index (MOCI) and the Universal Thermal Climate Index (UTCI) by means of an experimental field survey carried out in Rome (Italy). The GOCI reported a total percentage of correct predictions of 27.8%, higher than the PMV (27.7%), PET (25.4%) and UTCI (23.0%) but lower than the MOCI (32.2%). The higher predictive ability of this last index is due to the fact that it was specifically meant for the Mediterranean population. According to Spearman's rho measure of correlation and symmetrical measure of association Gamma calculations, the GOCI was the most sensitive index and it can be used to predict outdoor thermal comfort in areas devoid of studies about specific indexes.

Modelled spatiotemporal variability of outdoor thermal comfort in local climate zones of the city of Brno, Czech Republic

This study uses the MUKLIMO_3 urban climate model (in German, Mikroskaliges Urbanes KLImaMOdell in 3-Dimensionen) and measurements from an urban climate network in order to simulate, validate and analyse the spatiotemporal pattern of human thermal comfort outdoors in the city of Brno (Czech Republic) during a heat-wave period. HUMIDEX, a heat index designed to quantify human heat exposure, was employed to assess thermal comfort, employing air temperature and relative humidity data. The city was divided into local climate zones (LCZs) in order to access differences in intra-urban thermal comfort. Validation of the model results, based on the measurement dates within the urban monitoring network, confirmed that the MUKLIMO_3 micro-scale model had the capacity to simulate the main spatiotemporal patterns of thermal comfort in an urban area and its vicinity. The results suggested that statistically significant differences in outdoor thermal comfort exist in the majority of cases between different LCZs. The most built-up LCZ types (LCZs 2, 3, 5, 8 and 10) were disclosed as the most uncomfortable areas of the city. Hence, conditions of great discomfort (HUMIDEX >40) were recorded in these areas, mainly in the afternoon hours (from 13.00 to 18.00 CEST), while some thermal discomfort continued overnight. In contrast, HUMIDEX values in sparsely built-up LCZ 9 and non-urban LCZs were substantially lower and indicated better thermal conditions for the urban population. Interestingly, the model captured a local increase of HUMIDEX values arising out of air humidity in LCZs with the presence of more vegetation (LCZs A and B) and in the vicinity of larger bodies of water (LCZ G).

A Human-Centered Approach to Enhance Urban Resilience, Implications and Application to Improve Outdoor Comfort in Dense Urban Spaces

The concept of resilience in urban design and decision-making is principally focused on change instead of resistance over an adaptive process. For cities, this concept in a broader scale means how to withstand unforeseen events that will fundamentally amend the city’s wellbeing, rather than being stabilized and protected. The same concept is applicable for outdoor comfort as an adaptive approach to compensate extreme heat waves and health risk conditions. This chapter presents methods, tools, and applications to enhance urban resilience at a micro scale looking for correlations between environmental factors and human behavior in terms of outdoor comfort.

THE CLIMATE SENSITIVE DESIGN IN HOT-HUMID URBAN DESIGN

Urban and microclimate have intense relationship that affecting each other’s. Specific urban structure can affect microclimate because of high radiation generated. In the other side, urban structure blocks distribution of incoming wind. Urban structure changes how the microclimate influences the city. The successful urban structure can impact how outdoors open spaces are used meanwhile good open spaces are affected by how comfortable can be accepted. Microclimate control is the first element has to be considered to design comfortable outdoor open spaces. This research used monthly mean air temperature, relative humidity, precipitation, vapor pressure, and wind velocity for the period 2009–20014 to simulate any type of microclimate situation that influence thermal comfort in the urban context. Data were collected from 3 selected meteorological stations in Jakarta and websites. PET (physiological equivalent temperature) is used to assess the value of thermal comfort in outdoor spaces. This study shows that hot-humid city has abundance solar radiation, which influences the heat in the urban area that need to be released immediately meanwhile because of the urban structure reduce the wind velocity that enter into the urban area, the city does not has strong energy to release the heat. So urban structure has to be well designed to make wind can release the heat trapped in the urban area.

The influence of bioclimatic urban redevelopment on outdoor thermal comfort

One of the greatest environmental challenges for the sustainability of future cities is the mitigation of the urban heat island phenomenon and thus, improvement of outdoor comfort conditions for people. The emphasis of this work is to analyze how mitigation techniques in a dense urban environment affect microclimate parameters and outdoor thermal comfort. The quantitative differentiation of outdoor thermal comfort conditions through bioclimatic urban redevelopment for an area in the city of Serres, Greece is investigated. The main bioclimatic interventions concern the application of cool paving materials, the increase of vegetated areas and the creation of water surfaces. The analysis and comparison are performed for a hot summer day with the ENVI-met model. Software simulations regarding microclimatic and outdoor thermal comfort conditions are performed for the daytime period 06.00–20.00 (14h) at the height of 1.8m from the ground. The examined parameters are air temperature, surface temperature and mean radiant temperature (Tmrt). The evaluation of outdoor thermal comfort conditions is conducted using the index PMV (Predicted Mean Vote), adapted for outdoor conditions. The results of simulations are discussed regarding the assessment of bioclimatic interventions.

Biometeorological indices explain outside dwelling patterns based on Wi-Fi data in support of sustainable urban planning

This study presents a novel approach to validate the capability of biometeorological indices to predict the likelihood of urban dwellers to be outside during midday. Over a period of ten months three Wi-Fi scanners were used in a public courtyard in Cambridge, MA, to record outside dwelling patterns. Based on encrypted MacIDs courtyard attendees could be divided into 16,000 regulars and 676,000 visitors. Universal Thermal Climate Index (UTCI) predictions based on a combination of measured microclimatic conditions and mean radiant temperature simulations using ENVI-met were shown to strongly correlate with the number of regulars present during lunchtime with coefficients of determination (R2) of 92% during spring and 70% during summer/fall, respectively. Lunchtime attendance peaked for UTCI values in the thermal comfort and moderate heat stress ranges. In parallel, the probability for regulars to have lunch outside more than doubled during those UTCI conditions and the median lunchbreak length increased from 8 min to 12 min. These findings suggest that UTCI can be used as a reliable environmental performance metric to support the design and preservation of comfortable outdoor spaces. The reported use of public Wi-Fi data can help city governments to better understand – and potentially improve – the use of outdoor spaces while maintaining the privacy of their constituents.

Outdoor Thermal Comfort in a Transitional Space of Canopy in Schools in the UK

There has been a significant increase in opportunities to improve school environments in the UK. There has, however, been little study on the design of sheltered transitional spaces, despite growing architectural demand for this, examples of which can be easily found in most primary schools in the UK. Computer simulations (Rayman, Ecotect and Winair4) were performed to identify the influence of different parameters: that of having a canopy; the effect of the transmissivity of the canopy material (three transparencies 0%, 50% and 90% were considered); orientation (four orientations—north, east, south and west—were considered); and location (three cities: London, Manchester and Glasgow). The combined effects of canopy transparency and orientation were shown to be critical design considerations in affecting comfort conditions in outdoor spaces. It was found that outdoor comfort conditions in the transitional space can be enhanced by 41.5% in August by choosing a canopy of 0% transparency, compared with a canopy of 90% transparency in London. The fixed canopy with a higher transparency helped to increase outdoor thermal comfort in Glasgow, while one with a lower transparency showed better performance during summer in London. This research will help design environmentally sophisticated transitional spaces in schools.

Influence of the Ground Greening Configuration on the Outdoor Thermal Environment in Residential Areas under Different Underground Space Overburden Thicknesses

In the underground space development of residential areas, outdoor thermal environments at the pedestrian level greatly depend on the ground greening configuration, which is in turn affected by the overburden thickness of the underground space (OTUS). However, few studies have considered the effects of OTUS on the ground greening configuration and the further effects of the ground greening configuration on the outdoor thermal environment. This study aimed to provide insights into the design of OTUS for improving outdoor thermal environments. Two residential areas with row and enclosed layouts in Nanjing, China, were numerically studied using the computational fluid dynamics (CFD) simulation software ENVI-met. Outdoor thermal environments in the two residential areas, which had the same greening coverage rate, were simulated under different OTUSs and ground green configurations. The results indicate that to create a comfortable outdoor thermal environment, the OTUS should be designed to satisfy the requirement for planting small trees. If this requirement cannot be adequately satisfied, individuals can also set up tree wells or add soil on top of underground structures to plant small trees, and establish an OTUS that can satisfy the requirement of planting large shrubs in other areas.

On the impact of the wind speed on the outdoor human comfort: a sensitivity analysis

The energy demand of buildings and outdoor human comfort are key elements of a sustainable urban design. The wind speed has an enormous impact on thermal sensation, but the sensation itself is hard to quantify. The objective of this paper is to understand how the wind influences thermal energy exchanges, and to quantify its impact on outdoor thermal sensation. In order to do so, three outdoor comfort models were selected. Each thermal model was then calculated for the EPFL campus (Switzerland) by coupling the software tools CitySim and RayMan. In order to factor the importance of local meteorological data, two different sources of data are used: the software Meteonorm and recorded onsite data. Results obtained underline the impact of the wind speed on the thermal perception of pedestrians, describing the sensitivity of each of the thermal models, as well as the environmental characteristics.

Implications of climate and outdoor thermal comfort on tourism: the case of Italy

Whether a journey is pleasant or not usually depends on the climatic conditions which permit to perform outdoor activities. The perception of climatic conditions, determined by physiological and psychological factors, can vary according to different adaptation phenomena related to the person involved and the weather conditions of the place where they live. Studying the bioclimatology of a country characterized by a high flux of tourism, as e.g. Italy, can provide some important information about where and when is it better to visit a place. Some differences have to be specified though, like the local tourism, which is used to that type of climate, and international tourism, which is formed by people coming from countries with different types of climates. Therefore this paper examined the climatic conditions and outdoor thermal comfort through the Mediterranean Outdoor Comfort Index (MOCI) for local tourism and through the predicted mean vote (PMV) for international tourism. The cities examined were three (Venice, Rome and Palermo located in the North, Centre and South of Italy, respectively), where average information were collected every week for an entire year. Finally, a map of the entire Italian territory reporting the seasonal average values of these indexes was also reported.

A methodology to evaluate outdoor microclimate of the archaeological site and vegetation role: A case study of the Roman Villa in Russi (Italy)

Extensive literature exists on the effects and risks on environmental products, and in particular on the vegetation in archaeological areas; vegetal framework, as is known, changes the microclimate conditions and may affect the conservation of an archaeological site.The objective is to verify the effects of the presence of trees on the outdoor microclimate in these areas to determine and assess the conservation strategies and outdoor comfort conditions. Software modelling is carried out with ENVI-MET V4, which allows the analysis of micro-climatic conditions of the area and the context of interactions with the vegetation. The research described in this article relates to the remains of which are surrounded by a plain of woodlands. The simulations have allowed us to understand the real influence of trees on conservation ruins, also defining the perceived well-being benefits for visitors.Result simulation about climate condition in study area show that distribution of air temperature varies depending on the presence of trees and trees species, also mean radiant temperature, while the value of Relative Humidity depend on both tree evopotranspiration and weather-climatic conditions of the season.