Tsichritzis, L. and Nikolopoulou, M. (2019). The effect of building height and façade area ratio on pedestrian wind comfort of London. Journal of Wind Engineering and Industrial Aerodynamics [Online] 191:63-75. Available at: https://doi.org/10.1016/j.jweia.2019.05.021.
The evaluation of wind environment has been receiving increasing attention as it has been associated with issues related to the quality of the urban climate, such as heat island intensity and air pollution, affecting health and wellbeing in large metropolitan areas. Focusing on the context of London, this study aims to associate pedestrian level wind comfort with the characteristics of urban morphology that incorporate information about the height variability and the vertical dimensions of buildings. More than 20 case studies of different configurations and dimensions 500 × 500 m were examined through CFD simulations. For each case study, eight wind directions were tested and the BRE wind comfort criteria were implemented for the different outdoor human activities. The results reveal a strong connection between the ground level mean wind speed ratio and the development of acceptable or tolerable wind conditions for pedestrians. From the morphological indicators examined, façade area ratio was the most dominant on mean wind speed ratio and on the percentage of outdoor space which is comfortable for certain activities, especially for increasing values of plan area ratio. The results of the study indicate that façade area ratio should be taken into consideration for assessing pedestrian level wind environment.
Vasilikou, C. and Nikolopoulou, M. (2019). Outdoor thermal comfort for pedestrians in movement: thermal walks in complex urban morphology. International Journal of Biometeorology [Online]. Available at: https://doi.org/10.1007/s00484-019-01782-2.
In the discussion of designing for a healthier city, people in movement between interconnected spaces perform a non-sedentary activity enhancing sustainability and well-being. However, adverse weather conditions may create uncomfortable thermal sensations that change or ruin the experience of people walking outdoors. This paper is presenting the findings of a 3-year study on the perceptual variation of thermo-spatial conditions and comfort state for pedestrians moving between interconnected spaces. Thermal walks were organised in two European pedestrian routes of 500-m length. The structured walks were conducted with simultaneous microclimatic monitoring and field surveys of thermal perception based on 314 questionnaires, with a focus on the variation of comfort states. The findings suggest that spaces in sequence do not affect significantly microclimatic variation but have a large impact on the dynamic thermal perception of pedestrians. Interconnected spaces of high density result in a differentiation of thermal pleasantness between streets and squares. The aspect of movement along with complexity in urban morphology along a sequence enhances diversity in thermal sensation. This understanding opens possibilities in developing a multisensory-centred urbanism, where the experience of the thermal environment plays an integral role for perception-driven and healthier urban design.
Sivitanidou, A. and Nikolopoulou, M. (2019). The Intuitive Bioclimatism and Embedded Sustainability of Cypriot Vernacular Farmhouses, as Principles for their Strategic Restoration and Reuse. IOP Conference Series: Earth and Environmental Science [Online] 329:12033. Available at: https://doi.org/10.1088/1755-1315%2F329%2F1%2F012033.
This research aims to investigate the bioclimatic design, sustainability and environmental behaviour of Cypriot vernacular farmhouses, as part of small-scale family-owned farmsteads. These farmhouses, located in village outskirts, are still in operation, greatly supporting the primary sector of Cypriot economy. Current uses have conduced arbitrary modifications in their morphology, layout, construction and usage, which in the past had contributed positively to thermal comfort and household autonomy. In the present, these modifications caused farmhouses to become climatically inept, devoid of Bioclimatism and Sustainability. This research employs multiple case studies with a fully-integrated mixed-methods design. Findings are drawn via triangulation of qualitative and quantitative data from ethnographic participant observation, post-occupancy evaluation survey, interviews, in-situ documentation and environmental monitoring. Initial findings show that there is a tangible and intangible relationship between the dwelling, its inhabitants and the environment, strengthened in time due to tradition, accumulated knowledge and experience, and born out of necessity, scarcity and practicality. It is an interdependent, dynamic and adaptive reciprocity, induced by the complex interplay of socio-cultural, economic, technological, aesthetic and environmental factors. The end result was for bioclimatic design to be applied intuitively and sustainability to be embedded in the form, configuration, construction and operational modes of farmhouses. As Cyprus attempts to conform to its EU obligations regarding the sustainable development of rural environments and make the transition towards nearly-zero energy buildings, the Cypriot vernacular farmhouse can offer valuable lessons in building design and performance, whilst provide clear guidance for its strategic restoration and reuse.
Aljawabra, F. and Nikolopoulou, M. (2018). Thermal comfort in urban spaces: a cross-cultural study in the hot arid climate. International Journal of Biometeorology [Online]. Available at: https://doi.org/10.1007/s00484-018-1592-5.
This cross-cultural research is an inaugural attempt to investigate the outdoor thermal comfort and the effect of cultural and social differences in hot arid climates. Case studies were carefully selected in two different parts of the world (Marrakech in North Africa and Phoenix, Arizona, in North America) to represent two different cultures in similar climatic context. Field surveys, carried out during winter and summer, included structured interviews with a standard questionnaire, observations and microclimatic monitoring. The results demonstrate a wide thermal comfort zone and prevalence of air-conditioning influencing thermal comfort requirements. The work also provides evidence of substantial cross-cultural differences in thermal comfort requirements between residents in Marrakech and Phoenix. It shows that adaptive measures, such as level of clothing, changing place, cold drinks consumption and thermal experience, varies between cultures and this influences the thermal evaluation of visitors in outdoor spaces in the hot arid climate. Evidence between the time spent in outdoor spaces and thermal expectations has been found. Moreover, environmental variables such as air temperature and solar radiation have a great impact on the use of the outdoor spaces in the hot arid climate and may determine the number of people in urban spaces. The study also identified significant differences in thermal comfort requirements between different socio-economic groups, highlighting the need for comfortable open spaces.
Adekunle, T. and Nikolopoulou, M. (2018). Post-occupancy evaluation on people’s perception of comfort, adaptation and seasonal performance of sustainable housing: a case study of three prefabricated structural timber housing developments. Intelligent Buildings International [Online]. Available at: https://doi.org/10.1080/17508975.2018.1493677.
This paper discusses the results of the post-occupancy evaluation conducted in three-prefabricated timber housing developments. The study investigated occupants’ perception of comfort, adaptation to the thermal environment, and seasonal performance of the buildings. The buildings are constructed with engineered timber products (SIPs and CLT). The survey was conducted in the summer, but it also evaluated the performance of the buildings in winter. The results show 81% of the respondents feel ‘warm’ in summer. More than 50% of the respondents feel ‘neutral’ or ‘slightly warm’ in winter. Over 90% of the participants con?rmed the use of control with higher control satisfaction. Higher control satisfaction votes observed in one of the buildings are found to be strongly in?uenced by the occupancy period and ownership status. The respondents who are satis?ed with control perceived a high level of control across the case study buildings. The importance of control for thermal comfort/satisfaction may be a contributing factor as control increases; a key suggestion for widening the adaptive actions of people in buildings. Overall, the results showed the occupants did not perceive extreme summertime overheating at the buildings, despite higher thermal sensation votes (summer) recorded during the survey. The study provides an insight into occupants’ perception of comfort and adaptation in the buildings. The study identi?es the signi?cant impact of control on occupants’ comfort and adaptation. The paper concludes that the buildings perform better in winter than summer.
Chatzipoulka, C., Compagnon, R., Kaempf, J. and Nikolopoulou, M. (2018). Sky view factor as predictor of solar availability on building façades. Solar Energy [Online] 170:1026-1038. Available at: https://doi.org/10.1016/j.solener.2018.06.028.
Solar availability on urban façades varies signifcantly, affected by obstructions by nearby buildings as well as orientation. A convenient way to evaluate their solar energy potential is deemed to facilitate the task of architects in increasing the use of photovoltaic systems and, thus solar energy generation in the urban environment. This study explores to what extent the sky view factor (SVF), a measure of the openness of a point to the sky, can be employed for evaluating solar irradiation of façades in complex urban scenes. For this purpose, extensive statistical analysis was performed testing the correlation of SVF with solar irradiances for 30 orientations, considering three European climates (i.e. Athens, London and Helsinki), and three periods (i.e. year, January and July). Special emphasis is put on global irradiance, which expresses the sum of three solar components, i.e. direct, diffuse and reflected. The study uses 24 urban forms - of 500 × 500 m area - in London for which SVF and solar irradiance simulations were performed for nine sky models (three locations by three periods). The results reveal a strong linear relationship (R2 > 0.8) between SVF and annual global irradiance in all orientations, at all three locations. In fact, as SVF was found to correlate well with both major solar components, direct and diffuse, it can be presumably used for predicting façades' annual solar irradiation at any location within the tested range of latitudes. With respect to monthly global irradiance, the relationship appears less consistent, affected by the increased sensitivity of the relationship of SVF with monthly direct irradiance to façade orientation and location's latitude, associated with the variations of solar altitude.
Pantavou, K., Lykoudis, S., Nikolopoulou, M. and Tsiros, I. (2018). Thermal sensation and climate: a comparison of UTCI and PET thresholds in different climates. International Journal of Biometeorololgy [Online] 62:1695-1708. Available at: https://doi.org/10.1007/s00484-018-1569-4.
The influence of physiological acclimatization and psychological adaptation on thermal perception is well documented and has revealed the importance of thermal experience and expectation in the evaluation of environmental stimuli. Seasonal patterns of thermal perception have been studied, and calibrated thermal indices’ scales have been proposed to obtainmeaningful interpretations of thermal sensation indices in different climate regions. The current work attempts to quantify the contribution of climate to the longterm thermal adaptation by examining the relationship between climate normal annual air temperature (1971–2000) and such climate-calibrated thermal indices’ assessment scales. The thermal sensation ranges of two thermal indices, the Universal Thermal Climate Index (UTCI) and the Physiological Equivalent Temperature Index (PET), were calibrated for three warm temperate climate contexts (Cfa, Cfb, Csa), against the subjective evaluation of the thermal environment indicated by interviewees during field surveys conducted at seven European cities: Athens (GR), Thessaloniki (GR),Milan (IT), Fribourg (CH),Kassel (DE), Cambridge (UK), and Sheffield (UK), under the same research protocol. Then, calibrated scales for other climate contexts were added from the literature,
and the relationship between the respective scales’ thresholds and climate normal annual air temperature was examined. To maintain the maximum possible comparability, three methods were applied for the calibration, namely linear, ordinal, and probit regression. The results indicated that the calibrated UTCI and PET thresholds increase with the climate normal annual air temperature of the survey city. To investigate further climates, we also included in the analysis results of previous studies presenting only thresholds for neutral thermal sensation. The average increase of the respective thresholds in the case of neutral thermal sensation was about 0.6 °C for each 1 °C increase of the normal annual air temperature for both indices, statistically significant only for PET though.
Chatzipoulka, C. and Nikolopoulou, M. (2018). Urban Geometry, SVF and Insolation of Open Spaces: the case of London and Paris. Building Research & Information [Online] 46:881-898. Available at: https://doi.org/10.1080/09613218.2018.1463015.
The radiant environment in open spaces is very sensitive to the surrounding built form, which determines their openness to the sky and exposure to the sun. This paper presents the analysis of 132 urban forms in London and Paris, two cities at similar geographical latitude, but of different urban geometry, focusing on the relationship between urban geometry and insolation of open spaces at neighbourhood scale. The method consists of three stages: (1) the geometric analysis of the urban forms, (2) their solar access analysis and (3) the statistical exploration of the results. Special emphasis is on the sky view factor (SVF), which is employed as an integrated geometry variable and environmental performance indicator. The comparative analysis of the two cities underlines the significance of urban layout for modifying the outdoor radiant environment, and reveals temporal characteristics of the relation between urban geometry and insolation of urban forms, induced by the varying solar geometry. Indicatively, the average mean ground SVF (mSVF) was found to be primarily affected by the quantitative characteristics of the open space, and able to predict average daytime insolation on March 21 and June 21 (R2?>?0.8), in both cities.
Kotopouleas, A. and Nikolopoulou, M. (2017). Evaluation of comfort conditions in airport terminal buildings. Building and Environment [Online] 130:162-178. Available at: https://doi.org/10.1016/j.buildenv.2017.12.031.
This paper presents findings from extensive field surveys in three airport terminal buildings in the UK, where the indoor environmental conditions were seasonally monitored and simultaneous structured interviews were conducted with 3087 terminal users. Moving beyond the recent work which brought to light the significantly differentiated requirements for thermal comfort between passengers and staff, this paper expands on the investigation of thermal and lighting comfort needs for the entire spectrum of terminal users under the scope of energy conservation. The results demonstrate the influence of the thermal environment on overall comfort and reveal consistent discrepancies, up to 2.1 °C, between preferred and experienced thermal conditions. Outdoor temperature dictated the clothing levels worn indoors, where the preferred thermal state was other than neutral. Terminal users demonstrated high levels of thermal tolerance and wide acceptability temperature ranges, averaging 6.1 °C in summer and 6.7 °C in winter, which allow for heating energy savings through the fine-tuning of indoor temperature set-points. Lighting comprises an additional field for energy savings through the maximisation of natural light. Bright rather than dim conditions were preferred and a preference for more natural light was evident even in cases where this was deemed to be sufficient, while the preference for more daylight was found to be time-dependent suggesting a link with the human circadian rhythm. The findings from this study can inform strategies aimed at reducing energy use in airport terminals without compromising comfort conditions as well as the design and refurbishment of new and existing terminals respectively.
Tseliou, A., Tsiros, I. and Nikolopoulou, M. (2017). Seasonal differences in thermal sensation in the outdoor urban environment of Mediterranean climates – The example of Athens, Greece. International Journal of Biometeorololgy [Online]. Available at: http://dx.doi.org/10.1007/s00484-016-1298-5.
Outdoor urban areas are very important for cities and microclimate is a critical parameter in the design process, contributing to thermal comfort which is important for urban developments. The research presented in this paper is part of extensive field surveys conducted in Athens aimed at investigating people’s thermal sensation in a Mediterranean city. Based on 2313 questionnaires and microclimatic data the current work focuses on the relative frequencies of people’s evaluation of the thermal along with the sun and wind sensations between two seasons trying to identify the seasonal differences in thermal sensation. The impact of basic meteorological factors on thermal discomfort with respect to season are also examined, as well as the use of the outdoor environment. Results show that psychological adaptation is an important contributing factor influencing perception of the thermal environment between seasons. In addition, the thermal sensation votes during the cool months show that individuals are satisfied to a great extend with the thermal environment whereas the combination of high air temperature, strong solar radiation and weak wind lead to thermal discomfort during summertime. As far as the appropriate urban design in the Mediterranean climate is concerned, priority should be given to the warm months of the year.
Queiroz da Silveira Hirashimaa, S., Sad de Assisb, E. and Nikolopoulou, M. (2016). Dataset on daytime outdoor thermal comfort for Belo Horizonte, Brazil. Data in Brief [Online] 9:530-535. Available at: http://dx.doi.org/10.1016/j.dib.2016.09.019.
This dataset describe microclimatic parameters of two urban open public spaces in the city of Belo Horizonte, Brazil; physiological equivalent temperature (PET) index values and the related subjective responses of interviewees regarding thermal sensation perception and preference and thermal comfort evaluation. Individuals and behavioral’ characteristics of respondents were also presented. Data were collected at daytime, in summer and winter, 2013. Statistical treatment of this data was firstly presented in a PhD Thesis  providing relevant information on thermal conditions in these locations and on thermal comfort assessment. Up to now, this data was also explored in the article “Daytime Thermal Comfort in Urban Spaces: A Field Study in Brazil” . These references are recommended for further interpretation and discussion.
Christina, C., Raphaël, C. and Marialena, N. (2016). Urban geometry and solar availability on façades and ground of real urban forms: using London as a case study. Solar Energy [Online] 138:53-66. Available at: http://dx.doi.org/10.1016/j.solener.2016.09.005.
Availability of solar radiation in the urban environment is determined to a great extent by urban geometry, namely how densely built-up an area is and how the given built volume is distributed spatially within the site. This paper explores relationships between urban geometry and solar availability on building façades and at the pedestrian level, with implications for buildings’ passive potential and outdoor thermal comfort, respectively. The study was based on the morphological and solar analysis of 24 urban forms of London, covering a wide range of built density values found across the city. Two aspects of solar availability were investigated at the neighbourhood scale, through statistical analysis: i) the relationships between urban geometry variables and solar availability indicators in different time periods, and ii) the seasonal solar performance of urban forms’ façades and ground.
Apart from the strong, negative effect of density, the analysis revealed that solar availability on ground and façades is significantly affected by urban layout. Mean outdoor distance, site coverage, directionality and complexity were the most influential for the solar performance of open spaces; whilst building façades were mostly affected by complexity, standard deviation of building height and directionality. However, direct solar irradiance on ground and façades was found to be influenced by different variables in January and July, which is attributed to the different solar altitude angles. Related to that, urban forms have been identified that present higher irradiance values in January and lower in June when compared to others. Considering temperate climates, these examples highlight the potential for enhancing the seasonal solar performance of existing and future urban developments. Finally, the seasonal effect on solar availability appears to be much more pronounced for ground with its mean direct irradiance value increasing on average by a factor 15, from January to July, while for façades the increase is only by a factor 2.6.
Hirashima, S., de Assis, E. and Nikolopoulou, M. (2016). Daytime thermal comfort in urban spaces: A field study in Brazil. Building and Environment [Online] 107:245-253. Available at: http://dx.doi.org/10.1016/j.buildenv.2016.08.006.
Adekunle, T. and Nikolopoulou, M. (2016). Thermal comfort summertime temperatures and overheating in prefabricated timber housing. Building and Environment [Online] 103:21-35. Available at: http://dx.doi.org/10.1016/j.buildenv.2016.04.001.
Kotopouleas, A. and Nikolopoulou, M. (2016). Thermal comfort conditions in airport terminals: Indoor or transition spaces?. Building and Environment [Online] 99:184-199. Available at: http://dx.doi.org/10.1016/j.buildenv.2016.01.021.
This paper reports on the investigation of the thermal comfort conditions in three airport terminals in the UK. In the course of seasonal field surveys, the indoor environmental conditions were monitored in different terminal areas and questionnaire-guided interviews were conducted with 3087 terminal users. The paper focuses on the thermal perception, preference and comfort requirements of passengers and terminal staff. The two groups presented different satisfaction levels with the indoor environment and significant differences in their thermal requirements, while both preferring a thermal environment different to the one experienced. The thermal conflict emerges throughout the terminal spaces. The neutral and preferred temperatures for passengers were lower than for employees and considerably lower than the mean indoor temperature. Passengers demonstrated higher tolerance of the thermal conditions and consistently a wider range of comfort
Kotopouleas, A. and Nikolopoulou, M. (2016). Thermal comfort conditions in airport terminals: Indoor or transition spaces?. Building and Environment 99:184-199.
This paper reports on the investigation of the thermal comfort conditions in three airport terminals in
the UK. In the course of seasonal field surveys, the indoor environmental conditions were monitored in
different terminal areas and questionnaire-guided interviews were conducted with 3087 terminal users.
The paper focuses on the thermal perception, preference and comfort requirements of passengers and
terminal staff. The two groups presented different satisfaction levels with the indoor environment and
significant differences in their thermal requirements, while both preferring a thermal environment
different to the one experienced. The thermal conflict emerges throughout the terminal spaces. The
neutral and preferred temperatures for passengers were lower than for employees and considerably
lower than the mean indoor temperature. Passengers demonstrated higher tolerance of the thermal
conditions and consistently a wider range of comfort temperatures, whereas the limited adaptive capacity
for staff allowed for a narrower comfort zone.
Nikolopoulou, M., Martin, K. and Dalton, B. (2015). Shaping pedestrian movement through playful interventions in security planning: what do field surveys suggest?. Journal of Urban Design [Online]:1-21. Available at: http://dx.doi.org/10.1080/13574809.2015.1106913.
The control and shaping of pedestrian movement recurs as an aspect of security planning for crowded spaces. Using the concepts of triangulation, performance and flow, this paper presents a series of experiments designed to shape pedestrian movement patterns in public spaces in different spatial and operation contexts, by eliciting noticeable behaviours and disrupting routine use of space. The hypothesis investigated is that playful, non-obstructive interventions foster a positive social experience yet can be used to shape pedestrian movement. The interventions examined were around the themes of floor marking and mirrors. Analysis demonstrated that the interventions were able to create zones of attraction and exclusion, engage people’s curiosity and elicit playful actions. Habituation, goal-directed behaviour and the influence of increased cognitive load at personal level were all important factors responsible for reducing the level of engagement with an intervention. The results suggest that increased understanding between environmental and interpersonal stimuli and behavioural responses can provide guidance in using socially acceptable design interventions to influence use of space in different operational contexts, contributing to sustainable security.
McGilligan, C., Natarajan, S. and Nikolopoulou, M. (2011). Adaptive Comfort Degree-Days: an index to compare adaptive comfort standards and estimate changes in energy consumption for future UK climates. Energy and Buildings [Online] 43:2767-2778. Available at: http://dx.doi.org/10.1016/j.enbuild.2011.06.037.
This paper introduces the concept of the Adaptive Comfort Degree-Day, a temperature difference/time composite metric, as a means of comparing energy savings from Adaptive Comfort Model standards by quantifying the extent to which the temperature limits of the thermal comfort zone of the Predicted Mean Vote Model can be broadened. The Adaptive Comfort Degree-Day has been applied to a series of climates projected for different locations (Edinburgh, Manchester and London) under different emissions scenarios in the United Kingdom for the 2020s, 2030s, 2050s and 2080s. The rate at which energy savings can be achieved by the European adaptive standard EN15251 (Category II) was compared with the ASHRAE 55 adaptive standard (80% acceptability) during the cooling season. Results indicate that the wider applicability of the European standard means that it can realise levels of energy savings which its counterpart ASHRAE adaptive standard would not achieve for decades.
Nikolopoulou, M. (2011). Outdoor thermal comfort. Frontiers in Bioscience [Online] S3:1552-1568. Available at: http://dx.doi.org/10.2741/245.
A review of the various approaches in understanding outdoor thermal comfort is presented. The emphasis on field surveys from around the world, particularly across Europe, enables us to understand thermal perception and evaluate outdoor thermal comfort conditions. The consistent low correlations between objective microclimatic variables, subjective thermal sensation and comfort outdoors, internationally, suggest that thermophysiology alone does not adequate describe these relationships. Focusing on the concept of adaptation, it tries to explain how this influences outdoor comfort, enabling us to inhabit and get satisfaction from outdoor spaces throughout the year. Beyond acclimatization and behavioral adaptation, through adjustments in clothing and changes to the metabolic heat, psychological adaptation plays a critical role to ensure thermal comfort and satisfaction with the outdoor environment. Such parameters include recent experiences and expectations; personal choice and perceived control, more important than whether that control is actually exercised; and the need for positive environmental stimulation suggesting that thermal neutrality is not a pre-requisite for thermal comfort. Ultimately, enhancing environmental diversity can influence thermal perception and experience of open spaces.
Nikolopoulou, M., Kleissl, J., Linden, P. and Lykoudis, S. (2011). Pedestrians’ perception of environmental stimuli through field surveys: focus on particulate pollution. Science of the Total Environment [Online] 409:2493-2502. Available at: http://dx.doi.org/10.1016/j.scitotenv.2011.02.002.
The connection between perception of individual exposure to different environmental stimuli; microclimate, noise and especially particulate matter (PM) was examined. Microclimate, noise and PM were monitored during field surveys with 260 questionnaire-guided interviews at a road construction site and a traffic site on the UC San Diego campus. The overall comfort was determined primarily by the thermal environment. The air quality was considered to be poor by 42% of the interviewees at the construction site, which was burdened with higher PM counts and sound levels. Overall, higher PM concentrations were correlated with perception of poor air quality. Similarity between the overall air quality and how dusty it feels suggests that visual clues of PM, such as dust, affect the perception of air quality and pollution. The effect of medical or smoking history on the perceived air quality was also examined. People with a medical history of hay fever voted more frequently for poor air quality conditions than those without, whereas current smokers were the least sensitive to ambient air quality conditions. Through the exposure-response relationships between the various perception votes and PM, it was possible to predict perceived air cleanness using the PM count. Understanding the human assessment of environmental stimuli could inform the design and development of urban spaces, in relation to the allocation of uses and activities, along with air quality management schemes.
Tseliou, A., Tsiros, I., Lykoudis, S. and Nikolopoulou, M. (2010). An evaluation of three biometeorological indices for human thermal comfort in urban outdoor areas under real climatic conditions. Building and Environment [Online] 45:1346-1352. Available at: http://dx.doi.org/10.1016/j.buildenv.2009.11.009.
Three biometeorological indices were examined in terms of their potential to describe the actual thermal sensation as this is experienced by humans at areas with different climatological characteristics. The thermal comfort scales, as derived from using Physiological Equivalent Temperature (PET), the Temperature-Humidity Index (THI) and the wind chill index (K), were compared to Actual thermal Sensation Votes (ASV) data as expressed on a 5-point scale. These data were collected by surveys that covered all four seasons of the year and were conducted in seven European cities (Athens, Thessaloniki, Milan, Fribourg, Cambridge, Sheffield and Kassel). Results show that, for any given ASV class, the corresponding classes calculated according to PET, THI and K, present a strong correlation with the climatic mean temperature of the survey site, which in turn leads to misclassification of the thermal sensation. Accordingly, an effort was made to apply an adjustment to the indices based on climatic mean temperature. Only small improvements were observed on the performance of the indices.
Aljawabra, F. and Nikolopoulou, M. (2010). The influence of hot arid climate on the use of outdoor urban spaces and thermal comfort: do cultural and social backgrounds matter?. Intelligent Buildings International [Online] 2. Available at: http://dx.doi.org/10.3763/inbi.2010.0046.
Climate-sensitive open spaces within cities may benefit the three dimensions of sustainability affecting economic, social and environmental factors. Aiming to improve microclimatic conditions in urban spaces can enable people to spend more time outdoors, with the potential to influence the social cohesion of a space and increase economic activity. The wider aim of this research was to develop a better understanding of the complex relation between microclimate and human behaviour in open public spaces in hot arid climates. Case studies were carefully selected in two different parts of the world (Marrakech in North Africa and Phoenix-Arizona in North America) to represent a variety of users in similar climatic context. This enabled us to study the effects of the socio-economic and cultural diversity on thermal comfort, behaviour and use of space. Field surveys included structured interviews with a standard questionnaire and observations of the human activities, along with microclimatic monitoring, carried out during winter and summer 2008 and 2009. The analysis consisted of: the microclimatic influence on the thermal sensation, preference and people attendance; the effect of psychological adaptation on subjective thermal evaluation of outdoor spaces; and finally, investigation of socio-economic and socio-cultural impact on behaviour of people in outdoor space.
Nikolopoulou, M. and Lykoudis, S. (2007). Use of Outdoor Spaces and Microclimate in a Mediterranean Urban Area. Building and Environment [Online] 42:3691-3707. Available at: http://dx.doi.org/10.1016/j.buildenv.2006.09.008.
This paper presents some of the findings of the European project, RUROS, concentrating on the effect of microclimatic conditions on the use of open spaces in an urban Mediterranean environment. The findings confirm that there is a strong relationship between microclimatic conditions and use of open spaces. Regarding the users of open spaces, a sensitivity to the summer heat was apparent for the age category >65. The spatial distribution of the interviewees demonstrates that in summer, visitors prefer to sit in shaded areas, whereas in autumn and winter sunlit areas are more popular. Observations of the use of space revealed that air temperature and solar radiation were found to be the most dominant parameters in relation to the use of space, with wind speed and relative humidity having a weak effect. In general, people prefer shaded areas at higher air temperatures. However, as high air temperature is a factor contributing to discomfort, overall presence is reduced when air temperature rises significantly. The preference of sun, differs from season to season, depending on the activities taking place in the areas (either designated or not). The diurnal pattern of the use of space also reveals a strong dependency on meteorological parameters. Regarding the time of maximum attendance, this is found in the evening during summer, while there is a transition of the time of maximum attendance towards noon as the season progresses from summer to winter. Daytime attendance figures of autumn and winter are 300-400% higher than in the summer. The need open spaces cover and the social ties provided may also be traced by analyzing the social composition of the interviewees and the reasons bringing them in the space.
Nikolopoulou, M. and Lykoudis, S. (2006). Thermal Comfort in Outdoor Urban Spaces: analysis across different European countries. Building and Environment [Online] 41:1455-1470. Available at: http://dx.doi.org/10.1016/j.buildenv.2005.05.031.
This paper presents some of the findings of the European project, RUROS, primarily concerned with the environmental and comfort conditions of open spaces in cities. The results of the microclimatic and human monitoring, in relation to the thermal environment and comfort conditions in open spaces are presented. The database consists of nearly 10,000 from field surveys in 14 different case study sites, across 5 different countries in Europe. The findings confirm a strong relationship between microclimatic and comfort conditions, with air temperature and solar radiation being important determinants of comfort, although one parameter alone is not sufficient for the assessment of thermal comfort conditions. Overall comfort levels are over 75% for all cities on a yearly basis. There is also strong evidence for adaptation taking place, both physically, with the seasonal variation in clothing and changes to the metabolic rate, as well as psychologically. Recent experience and expectations play a major role and are responsible for a variation over 10 °C of neutral temperatures, largely following the profile of the respective climatic temperatures on a seasonal basis, across Europe. In this context, perceived choice over a source of discomfort is another important parameter for people in open spaces.
Nikolopoulou, M., Kotopouleas, A. and Lykoudis, S. (2018). From indoors to outdoors and in-transition; thermal comfort across different operation contexts. In: 10th Windsor Conference: Rethinking Comfort. Available at: http://windsorconference.com/.
This paper focuses on the investigation of thermal comfort conditions in three very different
operational contexts using meta-analysis of different studies within a similar climatic context in the UK. This
includes extensive surveys indoors from offices, outdoors from urban areas, as well as indoors from airport
terminals. Recent research in airport terminal buildings has highlighted that there are very different user groups,
with diverse requirements for thermal comfort in such facilities. The paper investigates the hypothesis that staff
working in the different areas have needs more similar to those of staff working in offices, while passengers use
the building as a transition area with very different requirements and hence closer to the outdoor environment.
Analysing and comparing the thermal comfort conditions from the different contexts, it explores the role of
adaptation for thermal comfort attainment and satisfaction with the environment and the similarities of very
different operational contexts in terms of their thermal comfort characteristics. Finally, the paper highlighted
techniques for the potential transformation of thermal comfort scales, which can enable comparison between
different types of surveys and inform the wider thermal comfort debate.
Watkins, R., Nikolopoulou, M., Giridharan, R. and Kotopouleas, A. (2015). The Performance of Natural Ventilation In A Dance Studio – Lessons From Tracer Gas Measurements And Control Integration. In: 31st International PLEA Conference, Passive Low Energy Architecture.
The naturally ventilated, three storey School of Arts Jarman Building provides two dance studios, an exhibition gallery, teaching rooms, video editing suites and offices. The main dance studio is double-height, has underfloor heating and accommodates sixty people. Fresh air enters from low level perimeter louvres and exits at high level through a stack that rises through the third storey to a stack terminal with motorized louvres. Tracer gas (CO2) measurements were used to measure the ventilation rate in conjunction with hot-wire anemometry in the stack tower. The results showed that when all air inlet and exit louvres were set to closed, the residual air flow up the stack was 0.33m3/s representing a potential heat loss of 9kW in winter at 0°C outside. When the louvres were all open, the air flow increased to between 0.49 and 0.62m3/s, a level consistent with the studio’s design occupancy. It was found that the studio’s 4m high perimeter curtains represent a barrier to fresh air entering the main room space and cause the incoming air to migrate upwards towards the stack exit and effectively bypass the central part of the studio. Tracer gas decay rates showed that the main space experienced an air exchange rate 50% less than that for the overall studio. An investigation of the controls also revealed that the underfloor heating system operated independently of the control of the stack ventilation system, leading to simultaneous heating and venting. The research shows the vital importance of prescribing contractually that key controls are integrated, that fresh air dampers are well-sealed when closed, and the importance of designing a fresh air supply that matches the way a space is used.
Chatzipoulka, C., Nikolopoulou, M. and Watkins, R. (2015). The impact of urban geometry on the radiant environment in outdoor spaces. In: ICUC9 9th International Conference on Urban Climate. Available at: http://www.meteo.fr/icuc9/.
Urban geometry, namely the quantitative relationship of building volumes and open spaces (i.e. built density) and their spatial configuration (i.e. urban layout), is a major modifier of urban microclimate. This paper presents the results of an ongoing research which explores the impact of urban geometry on the radiant environment in outdoor spaces, with direct implications for urban microclimate and outdoor thermal comfort. In particular, the research investigates the relationship between a set of urban geometric indicators (such as Built Density, Site Coverage, Mean building Height and Frontal Area Density) and Mean Radiant Temperature (Tmrt) at the pedestrian level, in different areas of London.
Three representative areas of London were selected to be studied; in central, west and north London which are of high, medium and low built density, respectively. Each area was divided into squares of 500m x 500m size, with a total of 84 urban squares included in the study. The methodology comprises three stages: (i) A set of simple geometric indicators have been computed for all urban squares using special algorithms written and executed in Matlab software. (ii) Radiation simulations have been performed for 10 days of a typical year in London, with the use of SOLWEIG software. SOLWEIG simulates hourly, 3-D radiation fluxes, incoming to / outgoing from the ground, spatial variations of Tmrt, Ground View Factor (GVF) as well as Sky View Factor (SVF). Sunny and cloudy days have been considered, evenly distributed in the year in order for the effect of solar angles to be examined. (iii) Statistical tests have been conducted for investigating the correlation between urban geometry, as expressed by the geometric variables, and hourly, average values of Mean Radiant Temperature in the outdoor spaces of the urban squares.
The simulation results show that at night-time and in fully overcast conditions, the outdoor spaces of central London’s urban squares are warmer than those of west and north London, due to greater longwave radiation emitted and reflected by building volumes. In contrast, on sunny days, average daytime Tmrt values have been found to be higher in North London’s urban squares due to the larger insolation of their outdoor spaces. Additionally, the statistical analysis has shown that in the absence of direct solar radiation, the correlation between the geometrical variables and average values of Tmrt is very high with an almost perfect linear relationship between the geometrical variables and average SVF values (r2= 0.980). In the presence of direct solar radiation, the strength of the correlation varies with the sun altitude angle; the higher the sun altitude angle, the higher the correlation. In particular, a threshold altitude angle of 20 degrees has been identified, above which the correlation of average Tmrt values with urban geometry approximates that of night-time / cloudy hours. Finally, further statistical tests showed that site coverage (built area over site area) and frontal area density (façades’ total area over site area) are the strongest indicators among those considered in the analysis.
Kotopouleas, A. and Nikolopoulou, M. (2014). Understanding Thermal Comfort Conditions in Airport Terminal Buildings. In: NCEUB. Available at: http://windsorconference.com/_archive/Proceedings_Windsor_Conference_2014.pdf.
This paper presents the results from the thermal comfort studies at three airport terminal buildings in the UK where seasonal on-site surveys were conducted. The investigation involved extensive monitoring of the indoor environmental conditions along with 3,087 questionnaire-guided interviews with terminal users. The paper quantifies the thermal requirements of the terminal population and focuses on the thermal perception of passengers and staff in different terminal spaces. The findings demonstrate the preference for a different thermal environment than the one experienced and that thermal neutrality is found to lie at lower temperatures than those experienced, suggesting an overheating issue, predominantly in winter. Passengers and staff present different satisfaction levels with the indoor environment while their thermal sensation is greatly affected from the characteristics and function of the terminal spaces.