Darunee Mongkolsawat

Is user satisfaction a good thermal performance indicator?

Abstract

Increasing demand for air-conditioned buildings in hot-humid countries is of concern to energy policy makers, as air-conditioning takes the largest proportion of building energy consumption. A vast number of studies in thermal comfort have suggested that thermal adaptability is the key to maintaining user thermal comfort whilst reducing cooling and/or heating energy. However, to apply this concept to existing non-residential buildings installed with air-conditioning remains difficult since it may affect user satisfaction and expectations.

To investigate the possibility of applying the adaptive thermal comfort theory to practice, the mixed-mode buildings in higher education sector in Thailand are chosen as the case study, since this building type has high potential to reduce the cooling energy by the adaptive thermal comfort approach. Twenty-four heads of facility managers in different faculties were interviewed regarding the thermal operations and the possibilities of implementing three given mixed-mode strategies in their existing buildings. The proposed mixed-mode strategies are (1) to use fans to assist air-conditioners and set thermostats one or two degrees higher to save energy, (2) to use fans and windows for the morning/evening classes and in the cool season, and (3) to preserve or increase naturally ventilated spaces.

From the interviews, most facility managers that provide no user control (nine faculties) over the thermal environment said that the three mixed-mode strategies were impossible while those who provide high user control (thirteen faculties) said the strategies were difficult. In contrast, one out of two interviewees who provide moderate user control confirmed that all three strategies are currently implemented in their faculty. Further interviews revealed that concerns of energy waste and user satisfaction were two main factors that influenced the level of thermal control given to end-users. However, in many cases user satisfaction became more powerful since it directly affects the relationships between service providers and users. While many facility managers thought it is necessary to take over user control to reduce energy waste, due to fear of complaints they compensated for the loss of user control by quick response when something went wrong. In nine cases, user demand for quick cool air was responded by space pre-cooling. That is, the rooms would be air-conditioned five to fifteen minutes before use. The interviewees said this was also to prevent users from setting the temperature too low, causing a premature air-conditioner breakdown.

Once the overall control has been taken from end-users, sole responsibility for negative feedback lies in facility management staff’s hand. In this situation, the staff seems to have a higher motivation to maintain user satisfaction which probably results in over-provision of air-conditioning. This could explain the high expectation for air-conditioning and low possibilities to implement the mixed-mode strategies among the ‘no user control’ faculties.

In conclusion, this study suggests that the attempt to increase user satisfaction may not necessarily improve the building performance but rather weaken users’ adaptive capacity. While thermal adaptability is considered vital in an unpredictable climate, a thermal performance indicator that shows this aspect of a building should be developed alongside the user satisfaction.

(Keywords: Thermal comfort, user satisfaction, facility management, air-conditioning, higher education buildings)

Laura Patricia Narvaez Zertuche

The spatial distribution of economy and the morpho-logic of spatial networks

Abstract

The study of urban form is often related to how the physical complexities of the city are distributed at various scales, from the street patterns that build the structure of towns to the arrangement of street blocks, plots and individual buildings. Therefore, urban morphology can be understood more than the study of form itself. It is a centre for human activity in which different forces act together that shape and help develop our cities. This research is concerned with two such forces: economically and socially. In order to study form and structure under these two perspectives, it is proposed to relate bid-rent theory and how this relates to the different functional areas of the city, specifically in the formation and process of different centralities. Thus, the research proposes three general questions that relate the spatial distribution of economy and the configurational logic of spatial networks. The first general question is about how spatial accessibility can be priced, which in turn raises questions of how the physical patterns of the city is organised in terms of the proximity of different markets, namely real-estate properties. The second question addresses the issue of how the urban grid overlaps with patterns of location, land use and accessibility. The third general question deals with the relationship between urban form and economy as a two-fold perspective: one in which the relations of space act as the product of economic performance, and the reverse view of economy as the effect of urbanisation.

In studying how city centres are formed, literature suggests that the economic performance of urban form functions in a free market where the highest bidder will obtain more land. With this premise, the first assumption argues that distance is not only a cause of cost measured from place-to place, but also a resource that acquires value, becoming an asset of urban form. The formation of different local centres are accounted to the value of accessibility, in which the activities of the society can be reached, including the trade-off of benefits received through the connectivity of spaces. Therefore, a second assumption is that the geometrical properties of the urban grid are affected by price, which also has an effect on the distribution of activities. The final assumption is that in order to deepen our understanding of urban spaces in a localised economy it is necessary to unfold the spatial and economic actions as by-products of each other which also reflects the role of space in its social dimensions. In order to disentangle these questions and to test these hypotheses the City of Cardiff, Wales is explored using the theories and techniques of ‘Space Syntax’. The method combined detailed street-level mapping of land uses, building footprint and rental values with different types of topological, metric and angular distance measures. Using the ‘Bid Rent Curve’ model applied in the street network configuration, the first results have shown the physical properties of how a polycentric city like Cardiff is developed and how different ‘centralities’ within the city are generated accounting specific market distributions and the morphological properties formed within them.

(Keywords: urban morphology, bid-rent theory, spatial economics, Cardiff)

Lusine Tarkhanyan

A statistical perspective on locational analysis of crime

Abstract

Crime is not geographically constant. Some areas in the city have more crime than the others. Apart from socio-economic differences, it is suggestive that the distribution of geographical features and the way people navigate across the street grid also reflects the distribution of crime activates. The different mapping techniques developed for the past decades largely explore this dependency.

This presentation illustrates two different levels of crime mapping, where the same spatial statistical test is applied to point dataset aggregated, in one case, to the ‘areal’ level, and another, to the ‘segment’ level of analysis. The key difference in these spatial units is in modelling technique, mainly how point data is aggregated. The ‘areal’ level of analysis defines the case study area as polygons that contain crime incidents. The ‘segment’ level of analysis closely replicates the street grid and contains crime incidents that are closest to the given segment. Overall, the statistical test shows the general spread of crime distribution across the study area. Mainly, it tests how similar or different is the given location in comparison to the neighbouring locations in terms of crime intensity. The final output of the test illustrates the small areas of higher than average crime activity embedded in a large area of relative lower than average crime frequencies.

In the case of ‘areal’ unit of analysis the final map illustrates the hot spots of crime embedded in a larger area of relative calm. Although, this type of map shows specific places where the crime is concentrated, it is limited to predefined areal level, thus it is hard to depict the underling pattern of crime, because all locations with the same polygon are treated equally constant in crime rates. Moreover, depending on predefined scale of polygons, the hot spot might shift from one place to another. In contrary, the linear mapping represents finer grain of analysis, where the incident map shows the crime concentration along the streets. Here, the crime frequencies are not the same for the two neighbouring lines, furthermore the crime rates dramatically shift from one line to another, which is suggestive that the underling structure of street network might have an important effect on geographical variability of crime rates.

Even though, depending on the unit of analysis the distribution of crime values will differ considerably, this comparative test is suggestive that the ‘segment’ unit is more precise in modelling and quantifying the crime values, since it acknowledges the topology of street network. From the detection and prevention perspective, this level of analysis can considerably improve the geographical understanding of crime patterns, since it indicates streets that need more police attention or have high probability of being or becoming crime places.

(Keywords: crime mapping, spatial statistics, hot spot, street network)

Note: Lusine is jointly registered at the UCL Security Science Doctoral Research Training Centre and the Bartlett School of Graduate Studies

Garyfalia Palaiologou

Urban dialectics; a historic study of the domestic interface with the street

ABSTRACT

This research discusses historic transformations of the public-private interface of New York's row houses and London’s terraced houses. More particularly, the study considers morphological and configurational properties of the architectural, urban and social parameters that have shaped the residential streetscape in West Village, New York and in Islington, London.

The aim is to capture any characteristic generic physical properties of the built environment that might relate to potentials for flexibility in the ‘micro’ scale in order to respond to the continuously shifting socio-spatial circumstances over time. For this purpose, the study looks at the physical constitution of the urban streetscape in terms of the structured building-street relations. Considering the streetscape as a composition of building-street interfaces implies considering also a relation between the properties of the built form and the street network. In other words, the study examines the way properties of the street network, of the lot organisation and the building façade organisation might influence the evolution of a street segment over time in terms of its socio-spatial context. The methodological approach uses the analytical measures of space syntax, along with architectural and morphological analysis of urban form.

It is argued that citywide urbanisation processes affect shifts in building form, layout and use over time. The study aims to show the way historic changes in the urban grid and the ‘macro’ city scale imprint on the street façade and its transformation over time so as to construct compatible building-street interfaces alongside the evolving urbanisation. The selected cases studies aim to provide an insight in the way different city grid structures influence the way the dwelling/street interface evolved through time for two relevant housing typologies, such as the row house and the terraced house. New York and London are cities that present differences in their emergence, syntax and evolutionary processes: planned and orthogonal with significant three-dimensional development for New York, in contrast to a more village-like, irregular geometry and organic spatial evolution for London.

A first analysis of the New Work case study shows how the local scale of West Village area has adapted to New York's urbanisation by allowing for spatial - and therefore social and economic - diversity in the built fabric at all scales: façade, lot, block and, grid. The study shows that two opposing forces had an impact on the area’s neighbourhood profile: on the one hand, the historic preservation restrictions and regulations for the area’s row houses, which preserved in general their generic built form characteristics; and on the other hand, the extensions of main street arteries that increased the area’s connectivity to the rest of the city.

(Key words: historic transformations, urban interface, spatial diversity, space syntax)