Koen Steemers

Thermal comfort and psychological adaptation as a guide for designing urban spaces

Investigating thermal comfort conditions in outdoor urban spaces, has thrown some light on the complexity of the issues involved, demonstrating that a quantitative approach is insufficient in describing comfort conditions outdoors. It revealed that although microclimatic parameters strongly influence thermal sensation, they cannot fully account for the wide variation between objective and subjective comfort evaluation, whereas, psychological adaptation seems to becoming increasingly important. This paper concentrates on the issue of psychological adaptation: naturalness, expectations, experience (short-/long-term), time of exposure, perceived control and environmental stimulation, and presents an attempt to try and evaluate the relative impact of each of these parameters. Understanding the interrelationship between the different parameters of psychological adaptation would be of interest in order to compare their relative significance, and to assess their design role, that is whether design considerations would influence these parameters, or vice versa, whether they could influence design decisions. An awareness of these issues would be valuable to architects, planners and urban designers, not by the way of limiting possible solutions, rather by enriching the design possibilities.

Thermal comfort in outdoor urban spaces: understanding the human parameter

The research being undertaken seeks to achieve a better understanding of the richness of microclimatic characteristics in outdoor urban spaces, and the comfort implications for the people using them. The underlying hypothesis is that these conditions influence people’s behaviour and usage of outdoor spaces. The initial results demonstrate that a purely physiological approach is inadequate in characterising comfort conditions outdoors, and an understanding of the dynamic human parameter is necessary in designing spaces for public use. The thermal environment is indeed of prime importance influencing people’s use of these spaces, but psychological adaptation (available choice, environmental stimulation, thermal history, memory effect, expectations) is also of great importance in such spaces that present few constraints.

Energy and the city: density, buildings and transport

Cities by definition are a focal point of energy consumption. Their forms have a significant bearing on the balance of building and transport energy use, which are the two sectors that are directly affected by urban planning (the third being industrial). This paper establishes the relative magnitudes of building energy use in comparison to transport, and points out the interrelationships between the two in the context of the cities and of a temperate climate. The main part of the paper assesses the building energy trends and implications of urban form, with a particular reference to the effect of varying density, and presents strategic findings. It calls for continued research and development, particularly in the field of modelling the urban microclimate as a function of design, as well as comfort research with an emphasis on outdoor comfort. Urban microclimate and comfort are the themes of this journal, and this paper aims to set the scene.

Building form and environmental performance: archetypes, analysis and an arid climate

Abstract Leslie Martin and others at Cambridge University addressed the question “What building forms make the best use of land?” in a number of influential papers published in the late 1960s. They selected six simplified urban arrays based on archetypal building forms. Then they analysed and compared the archetypes in terms of built potential and day lighting criteria, eventually reaching the conclusion that courtyards perform best. Their results, which inspired a generation of designers, are briefly reviewed here and reassessed in environmental terms using innovative computer analysis techniques. Furthermore, the implications of their question, which to date has not addressed the link with climate, are explored using a case study in a hot-arid region.

Modelling domestic energy consumption at district scale: A tool to support national and local energy policies

This paper presents the development, evaluation and application of the Domestic Energy and Carbon Model (DECM) for predicting the energy consumptions and carbon dioxide emissions of the existing English housing stock. A novel feature of DECM is the adoption of an occupancy pattern model which is derived from the household employment status data. We believe this modification has significantly improved the accuracy of the estimation in space heating energy use. At national level, the model estimation of carbon emissions and gas and electricity consumptions are respectively 4.5%, 3.4% and 1.0% higher than the national statistics. At the sub-national level (Local Authority), two methods are used to produce estimations: one based on dwelling type and the other based on socio-economic class. For both methods, the correlations between the model estimations and the government records are statistically significant and substantial (all rs > 0.9 and ps<0.01). According to the results, it can be inferred that over 85% of the variance in dwelling energy consumptions and carbon emissions can be accounted for by dwelling type and the socio-economic class of households. The paper presents a local sensitivity analysis which examines the effects of various building fabric and service system parameters on the modelled average carbon emissions per dwelling. Based on the findings, a set of predictive charts are developed which can provide rapid estimations of the effect of various energy efficiency measures on dwelling energy consumptions and carbon emissions taking into account the potential rebound effect. In summary, this paper shows that the DECM model can be a useful tool to assist the formation of energy efficiency policies at both national and local levels.

Improvements to the Globe Thermometer for Outdoor Use

The rapid changes in radiant conditions outdoors, require a fast response globe thermometer. As part of a research project entitled “Thermal Comfort in Outdoor Urban Spaces”, extensive field studies are being carried out involving environmental monitoring and interviews, thus the development of such an instrument was crucial. This paper describes a series of parametric studies of five 38 mm-diameter globe thermometers, of different thickness and materials, with the objective of reducing the thermometers response time to approximately 4 min, similar to the duration of the interviews. Contrary to current belief, it is not only the slow heat transfer from the globe to the heat sensor that is responsible for long response times, but the heat capacity of the system as well, and by reducing it, shorter response times were achieved.

The Luminance Differences index: a new indicator of user preferences in daylit spaces

This paper presents part of the findings of a research project conducted at the Martin Centre University of Cambridge, which looked into how daylighting quality affects the users of a library interior. It discusses the importance of luminance in the field of view for the perception of quality and introduces a new index named Luminance Differences (LD) which represents luminance variability (‘noise’). It will be illustrated that this index was successful in relating to the users’ subjective assessments of daylight quality, suggesting that it can be used to predict user preferences in a daylit space.

LT Method 3.0 — a strategic energy-design tool for Southern Europe

The LT Method is an energy-design tool which responds to parameters available early in the design development. It provides an output of annual primary energy for lighting, heating cooling and ventilation. This paper introduces LT 3.01, a version for Southern Europe which includes a procedure to evaluate the affect of shading devices on cooling loads and on lighting.

Environmental diversity in architecture

Part 1: Introduction 1. Environmental Diversity in Architecture Part 2 Framework 2. Social, Architectural and Environmental Convergence 3. The Ambiguity of Intentions 4. Human Nature 5. Designing Diverse Lifetimes for Evolving Buildings Part 3: Urban 6. Urban Diversity 7. Outdoor Comfort 8. Intermediate Environments 9. The Reverential Acoustic Part 4: Interior 10. Environmental Diversity and Natural Lighting Strategies 11. Daylight Perception 12. Exploring Thermal Comfort and Spatial Diversity Part 5: Design 13. Experiencing Climate: Architecture and Environmental Diversity

Ventilation strategies for urban housing: lessons from a PoE case study

Mechanical ventilation with heat recovery is still not widely used in UK housing, but with insulation and air-tightness standards becoming increasingly strict, it is likely to become more common. Operable windows are almost a given for housing and the UK climate is rarely extreme enough to restrict peoples use of those windows for natural ventilation. This is a potential problem for the use of heat-recovery systems and could greatly reduce their energy efficiency. The paper takes the Iroko housing scheme at Coin Street, London, as a post-occupancy evaluation (PoE) case study to investigate the questions raised with respect to how well the occupants of the houses cope with balancing both natural ventilation and mechanical systems to achieve thermal comfort energy efficiently. First, the optimum balance of mechanical and natural ventilation is estimated and used to determine the maximum potential saving it could give when compared with natural ventilation alone. Short-term monitoring of the building in question together with the results of questionnaires showed why this theoretical balance is not achieved and that the energy consumption is likely to be worse than for natural ventilation alone. Noise, perceived control, perceived freshness and misunderstanding are all discussed as possible causes for the apparent disjunction. Misunderstanding on the part of residents was shown to be a critical determinant, so information about the heat recovery system was distributed to the residents and the paper ends by looking at what theoretical energy savings might be made as a result of this act.