Thomas Parkinson

Thermal pleasure in built environments: physiology of alliesthesia

International standards that define thermal comfort in uniform environments are based on the steady-state heat balance equation that posits ‘neutrality’ as the optimal occupant comfort state for which environments are designed. But thermal perception is more than an outcome of a deterministic, steady-state heat balance. Thermal alliesthesia is a conceptual framework to understand the hedonics of a much larger spectrum of thermal environments than the more thoroughly researched concept of thermal neutrality. At its simplest, thermal alliesthesia states that the hedonic qualities of the thermal environment are determined as much by the general thermal state of the subject as by the environment itself. A peripheral thermal stimulus that offsets or counters a thermoregulatory load-error will be pleasantly perceived and vice versa, a stimulus that exacerbates thermoregulatory load-error will feel unpleasant. The present paper elaborates the thermophysiological hypothesis of alliesthesia with a particular focus on set-point control and the origins of thermoregulatory load-error signals, and then discusses them within the broader context of thermal pleasure. Alliesthesia provides an overarching framework within which diverse and previously disconnected findings of laboratory experiments, field studies and even comfort standards spanning the last 40 years of thermal comfort research can be more coherently understood.

Thermal pleasure in built environments: alliesthesia in different thermoregulatory zones

The principle of thermal alliesthesia indicates that the hedonic character of a thermal environment is determined as much by the general state of the subject as by the environment itself. An environmental stimulus that offsets or counters a thermoregulatory load error will be pleasantly perceived, and vice versa. Extant empirical evidence supporting thermal alliesthesia only exists for instances of core temperature deviation. Yet the reconciliation of alliesthesia with contemporary neurophysiological discourse (in the previous paper in this series) renders the concept directly relevant to everyday experiences in built environments where core temperature rarely deviates from neutral values. New experimental data are presented that explore alliesthesia in non-steady-state conditions across three different physiological states: thermoneutral; the upper and lower fringes of the thermoneutral zone; and mild excursions into the sweating and shivering regulatory zones. Thirteen human subjects evaluated the hedonic tone of a sequence of temperature step-changes and ramps. It was found that the psychophysiological principle of thermal alliesthesia operates within the thermoneutral zone, making it equally relevant to quotidian indoor environments as it is to the extremes found in traditional physiological research. Non-steady-state built environments can potentially offer spatial alliesthesia through carefully managed contrasts between local and mean skin temperature trends. Transitional zones are suggested as design solutions.

Thermal pleasure in built environments: spatial alliesthesia from contact heating

The comfort zone is bounded by thermal environmental conditions that may be described as acceptably cool or acceptably warm, and engineering out of existence these innocuous thermal conditions on the fringes of the adaptive comfort range may not be necessary. In contrast to the conventional understanding of local discomfort, spatial alliesthesia exploits corrective differences in the rate of change in skin temperature between individual body segments to elicit positive affective sensations. This paper examines reverse instances of local discomfort, or spatial alliesthesia, from warm contact stimuli applied to hand and feet when exposed to ambient conditions towards the lower margin of the comfort zone. It was found that subjects with moderate feelings of displeasure or even indifference were still capable of experiencing a pleasant response to localized thermal stimuli. Brief whole-body thermal pleasure was observed from in-situ skin temperature changes at a single distal body site. These effects were subtle and not universally experienced, so the success of their deliberate implementation in built environments depends heavily on some form of individual control. Spatial alliesthesia therefore complements the body of literature investigating personal environmental control and local thermal discomfort by providing a theoretical framework of thermal perception in non-neutral environments.

Thermal pleasure in built environments: spatial alliesthesia from air movement

ABSTRACT In recent years there has been a shift in research focus away from the negative effects of draught towards the positive benefits of air movement, particularly in the context of personal environmental control (PEC) systems. Thermal perception under targeted air movement is different from exposures in airflow uniformly distributed across the body, but is less well understood. Specification of performance criteria for PEC systems remains unresolved, as there are no clear conclusions regarding optimum target area, velocity ranges or patterns of velocity dynamics. This paper examines the effects of different local air-velocity profiles on thermal sensation and thermal pleasure experienced by human subjects near the upper boundary of the comfort zone, and interprets the findings within the theoretical framework of spatial alliesthesia. It was found that positive thermal pleasure can be achieved when contrasting relationships between local and global skin temperatures trends are established. The substantial body of research literature on local thermal discomfort can be coherently interpreted within the theoretical framework of spatial alliesthesia; local discomfort represents thermal alliesthesia with the incorrect polarity between local and global thermal states. Spatial alliesthesia therefore provides a conceptual framework to understand PEC systems and their potential to minimize occupant thermal dissatisfaction.