ID2: Multicriteria environmental perception
Thermal notations as a design tool: evaluating the thermal comfort of pedestrians moving in spatial sequences
Centre for Architecture and Sustainable Environment, University of Kent, United Kingdom
Thermal perception plays a major role in the pedestrian’s experience of complex urban environments, based largely in a continuous diversity of spaces, microclimates and comfort state. When moving in spatial sequences, the ability to measure thermal comfort forms a vital part of the design of comfortable urban spaces. This raises the question regarding an efficient and accurate way to evaluate thermal comfort in spatial sequences and how can this evaluation be transformed into an efficient urban design tool. Outdoor thermal comfort studies based on fieldwork tend to evaluate thermal comfort with an emphasis on the static experience of people in disconnected individual urban spaces. The impact of pedestrian movement and rapid passage from one space to the other on thermal perception, comfort and its subtle variations has not been sufficiently analysed. The author’s recent work has attempted to fill this gap by developing the methodology of thermal walks. This provided an efficient tool for evaluating thermal comfort along spatial sequences through the combination of microclimatic measurements and people surveys. The present study aims to focus on the critical task of making the results of “thermal walks” accessible to architects and urban designers. This is achieved with the creation of a standard of notation that codifies a wide range of objective and subjective measurements and facilitates their interpretation and use by the non-expert.
Thermal notations are a graphic representation tool that depicts both objective and subjective data of microclimatic conditions and their effect on thermal perception along a spatial sequence of spaces. The combination of all investigated parameters is based on spatial and climatic specificity, objective and subjective descriptors and evaluation of thermal comfort. By locating the spatial sequence on a plan or a section, the notational scheme can be understood as a layer of transparency added to traditional modes of depicting urban spaces. The descriptors provide a measured value of each microclimatic parameter. At the same time, subjective descriptors record the pedestrians’ perception of each objective parameter, allowing for an indication of prevailing influence between temperature, wind speed and solar radiation. Finally, this method of graphic representation provides a strong distinctive image for each thermal environment and the basis for a comparative thermal analysis between spaces. Thermal notation can be applied to the overall evaluation of a spatial sequence and the designer may use this tool to identify spaces of discomfort and propose design solutions to improve them. The present paper draws from fieldwork that took place in spring and summer 2014 in the city centre of Paris, in the context of a redevelopment project of a street sequence. This included simultaneous microclimatic monitoring and people surveys in structured thermal walks. The results are presented using the tool of thermal notations.
The evidence-based approach of the thermal notation tool shows the importance of pedestrians as generators of data in the evaluation of outdoor thermal comfort and spatial quality. Correctly interpreted, its contribution is vital and needs to be taken into account in the design of pedestrian networks identifying design improvements in spaces of movement and lingering. This opens the way towards the broad use of thermal notation and its effective integration in the design process. The thermal representation of urban space may lead to significant results about projects of pedestrianisation and spatial quality in everyday walking environments.
New qualitative methods to explore thermal perception in urban spaces
1Wageningen University, The Netherlands, Landscape Architecture; 2University of Kent, UK, Architecture Department
The concept of ‘outdoor thermal comfort’ relies on the way people experience the thermal environment through their thermal and other sensory perceptions. So, not only the physical factors that influence direct thermal sensation, but also cues that originate from other senses (e.g. visual or haptic) play a role in thermal perception. Therefore, outdoor thermal comfort cannot be expressed with precision exclusively through the use of thermal indices based on measurements. Indicators of outdoor thermal comfort also need to take other sensory experiences and spatial information into account. Given this context, individual thermal perceptions need to be described through qualitative information as well.
Various professions that shape the environment (e.g. architects, urban designers or landscape architects) strive to design for ‘outdoor thermal comfort’. And through their design interventions they can influence many factors with an impact on thermal perceptions such as microclimate, spatial configurations and ambiance of spaces. Hence, professions that shape the environment need to be provided with design guidelines that take this knowledge connecting thermal perception and design interventions into account.
Such a knowledge basis needs to be derived from monitoring human thermal perception related to the experience of the spatial environment. The methods to do so are inspired by environmental psychology methods such as interviews, ‘sensewalking’ and cognitive mapping techniques. These were translated into novel qualitative methods to study outdoor thermal comfort. They all rely on interviews with people in longitudinal studies, relating their thermal perception (long and short term) to spatial perceptions.
There are two distinct strands in this people-surveys approach: first, interviews can be conducted with people observing a space and assessing its thermal environment while standing, and second, ‘sensewalking’ interviews may be applied to collect subjective data on thermal comfort by pedestrians in movement.
The first type of surveys with people who assess their thermal perception while standing in a space can result in individual ‘mental microclimate maps’ that reflect the interviewee’s microclimate perceptions of sub- areas. A large amount of such maps can be overlayed and be summarized into common ‘mental microclimate maps’. Such common microclimate maps allow to draw generalized conclusions about the effect of spatial configurations on people’s thermal perceptions. Through the interviews, additional information can be gained about the perception of building materials, colours, etc. that influence the ambiance and how this relates to thermal perceptions. Additional microclimate measurements in the spaces studied allow to make comparisons between perceptions and measured data.
The method of ‘thermal walks’ addresses the simultaneous monitoring of microclimatic conditions and their experience by pedestrians. This method is based on point-to-point evaluation of the thermal perception and includes the combination of measuring objective microclimatic and spatial data with subjective responses by pedestrians.
Both methodological strands involve the transfer of interview data into representations such as ‘mental microclimate maps’, material perception maps, ‘thermal walk notations’, cross- sections or other spatial representations depicting people’s thermal and spatial perceptions. The measurement data help to calibrate the outcomes. Generally, the combination of both quantitative and qualitative methods has yielded reliable information describing thermal perception in relation to spatial characteristics.
Conclusions from these calibrated spatial representations can provide design guidelines that relate thermal perception and spatial design interventions. These design guidelines are useful for all professions who want to create thermally comfortable environments.
In our presentation, we will discuss a series of these new methods that have been applied in different European studies and reflect on their reliability in landscape and urban design research and the usefulness for practical applications.
Performance standard for tropical outdoors: A proposal in a time of climate change
Glasgow Caledonian University, United Kingdom
Unusual (>3 standard deviations above the base climate of 1951-1980) and unprecedented (>5 SD) heat extremes are expected to be the norm in much of tropical Asia and Africa in the near term even as these regions undergo transformational social and economic change. Consequently, tropical cooling load – much of which is currently latent due to low levels of economic development – is likely to be the dominant category of global energy demand. Yet, deep technological development and efficiency improvements in cooling systems are yet to be achieved. To make matters worse, cultural practices and attitudes limit adaptive possibilities to warmer temperatures even as the improving socio-economic conditions in the tropics lead to ‘thermal indulgence.’ One likely outcome of these developments is an unrealistic thermal comfort expectation in the tropics that is in direct conflict with the ‘global good’ of low/zero carbon economy. A compromise has to be reached based on societal priorities to ensure low energy expenditure without confining tropical dwellers to an inferior thermal comfort.
This paper argues that defining urban thermal comfort is critical to enhance the quality of life of tropical dwellers as their cities continue their historically unique urban trajectories. This also bodes well from an equity standpoint. However, care is needed to ensure such standards reflect the activity patterns unique to the region. Among other things, this will necessitate that the standards be coupled with non-thermal attributes of the urban commons.
Specifically, it will propose the linking of the ‘in’ to ‘out:’ it is necessary to specify not the indoor conditions to be achieved but the magnitude of change that ought to prevail between the ‘in’ and ‘out.’ It will focus on specifying standards for ‘cool’ urban spaces that enhance greater tolerance of warm conditions indoors. Finally, the standards need to be dynamic, responding to changes in urban microclimate as well as regional and/or global changes to climate. It will do so by proposing an ‘intermediate zone of comfort’ for the urban outdoors as a third category, and point to research documenting the value of individual and combined voluntary behaviours to ameliorate comfort by using local, adaptive strategies.
Such applications of adaptive strategies in the design of urban spaces will help tropical cities enhance their liveability in a time of extreme heat.