Marcel Schweiker

Verification of stochastic models of window opening behaviour for residential buildings

Based on the analyses of data from two distinct measurement campaigns conducted in residential indoor environments in Japan and Switzerland, we identify the specificities of occupants’ behaviour with respect to their interactions with windows, including the choice of opening angles for axial openings. As a first step, each dataset is analysed to develop separate predictive models which account for the specificities of window usage in the residential context. The predictive accuracy of these models is then challenged by validation on external data: using models inferred from data obtained from one survey, actions on windows are simulated for the other survey and the predictions are compared with observations. Dynamic models developed using data from office buildings as well as previously published models are also compared using this verification procedure. In the case of the Swiss dataset, these analyses demonstrate the ability of carefully formulated behavioural models developed from office environment data to reliably predict window usage in a residential context and vice-versa. However, we observe that the same models perform less satisfactorily in the prediction of window usage in Japan. From these results it seems that such models require specific calibration in the case of buildings equipped with an air-conditioning unit as was the case for the hot and humid summer climate of Japan.

Challenging the assumptions for thermal sensation scales

ABSTRACT Scales are widely used to assess the personal experience of thermal conditions in built environments. Most commonly, thermal sensation is assessed, mainly to determine whether a particular thermal condition is comfortable for individuals. A seven-point thermal sensation scale has been used extensively, which is suitable for describing a one-dimensional relationship between physical parameters of indoor environments and subjective thermal sensation. However, human thermal comfort is not merely a physiological but also a psychological phenomenon. Thus, it should be investigated how scales for its assessment could benefit from a multidimensional conceptualization. The common assumptions related to the usage of thermal sensation scales are challenged, empirically supported by two analyses. These analyses show that the relationship between temperature and subjective thermal sensation is non-linear and depends on the type of scale used. Moreover, the results signify that most people do not perceive the categories of the thermal sensation scale as equidistant and that the range of sensations regarded as ‘comfortable’ varies largely. Therefore, challenges known from experimental psychology (describing the complex relationships between physical parameters, subjective perceptions and measurement-related issues) need to be addressed by the field of thermal comfort and new approaches developed.

Explaining the individual processes leading to adaptive comfort: Exploring physiological, behavioural and psychological reactions to thermal stimuli

Behavioural, physiological and psychological adaptive processes are presumed reasons for the discrepancies between predicted mean vote and observed comfort votes during field studies. However, few are known about the individual portions of these processes. An experimental design was developed, which aims at identifying those portions and is meant for climate chambers with operable windows facing the exterior. This article looks in detail at behavioural and physiological reactions together with their effect on the perceived level of comfort. By means of multivariate regression analyses, these reactions are analysed in order to assess differences due to variations in indoor/outdoor conditions as well as the number of interactive opportunities. One of the results shows that the restriction to keep the window closed is counterbalanced by an increased amount of physiological reactions, such as an increased level of skin temperature, together with an increase of still permitted actions such as drinking. The results highlight the importance of detailed insights into single aspect of adaptive processes for a better understanding of the phenomenon called ‘adaptive comfort’. Such approach is novel and important because a detailed knowledge and quantification of the occupant’s comfort perception in naturally ventilated buildings permits a planning with less uncertainty.

Comfort-related feedforward information: occupants’ choice of cooling strategy and perceived comfort

ABSTRACT Approaches to provide feedforward information to building occupants about the impact of potential actions on individual thermal comfort levels are scarce. Even less is known about the effect of such information on the decision process of occupants to interact with their built environment and their level of comfort after such decisions. In a naturalistic study, participants (Nu2009=u200976) were given a choice of four actions to counteract thermal discomfort induced by constantly rising room temperatures: removing a piece of clothing, opening the window, switching on the ceiling fan or switching on the air-conditioning. After receiving information about the potential change in comfort and energy consumption of these options, they had to confirm or revise their choice. The vast majority of participants initially chose to open the windows (Nu2009=u200928) or remove a piece of clothing (Nu2009=u200937); only a few chose the ceiling fan (Nu2009=u20092) or the air-conditioning (Nu2009=u20099). About one-third (Nu2009=u200923) revised their choice of action; most of them (Nu2009=u200915) indicated an influence from the provided information. In conclusion, feedforward information can be a useful tool to combat overheating problems by increasing energy-aware behaviour and thermal acceptance.

Exploring internal body heat balance to understand thermal sensation

ABSTRACT A biological perspective is used to understand thermal sensation. The main premise is that thermal sensation serves an organism for the regulation of body temperature. A biological concept related to this premise is the physiological thermoneutral zone (TNZ). Within the TNZ the body can adjust body tissue insulation to maintain thermal balance and a stable core temperature. The approach presented here is based on the assumption that humans express neutral thermal sensation near the centre of their TNZ. To test this hypothesis, dTNZop is defined as the distance between measured operative temperature and the centre of the TNZ, and dTNZsk as the distance between measured mean skin temperature and the centre of the TNZ. The TNZ centre is calculated with a biophysical model using measured data from a climate chamber study with 16 female subjects. Regression between observed thermal sensation votes (TSV) and dTNZx revealed that the intercept corresponds with a slightly higher-than-neutral TSV and a strong linear relationship between TSV and dTNZop and dTNZsk. This approach shows great potential to improve the understanding of human thermal sensation in the context of physiology.

Study on the effect of preference of air–conditioning usage on the exergy consumption pattern within a built environment

According to previous work, preference is one major factor influencing occupants behaviour. This paper aims at identifying the magnitude preference on the exergy consumption pattern within a built environment. The comparison is made between one group claiming to like sleeping in air–conditioned spaces and the other claiming to dislike it. In conclusion, the exergy analysis showed that at the individual level, preference accounts for an exergy consumption rate up to 15% higher and that, at the community level, the exergy consumption rate of those preferring the AC–unit use is up to four times higher than that of the others.

Quantifying individual adaptive processes: first experiences with an experimental design dedicated to reveal further insights to thermal adaptation

Due to more frequent unusual weather phenomena being observed, there is an urgent need to identify and quantify the abilities of occupants to adapt to climate changes. The adaptive comfort model identifies behavioural, physiological and psychological adaptive processes. However, besides giving a statistical approximation of their general effect on the thermal perception vote, little is known about the individual contributions of the three types of adaptive processes to this effect. Knowing such portions would enable us to extend the existing comfort models in such a manner that they incorporate adaptive (re-)actions of the occupant. This could be used for the design of passively cooled buildings, particularly with regard to interaction between occupants and the building (envelope) for individual adjustment of the thermal indoor environment. This article describes first experiences with a new experimental design dedicated to reveal further insights to the adaptive processes along with the description of requirements for the inside–outside climate chamber currently under construction in Karlsruhe.

Laboratory Approaches to Studying Occupants

Laboratories offer the possibility to study occupant behavior in a very detailed manner. A wide range of indoor environmental scenarios can be simulated under precisely controlled conditions, and human subjects can be selected based on pre-defined criteria. The degree of control over experiments is high and a large number of physical, physiological, and psychological quantities can be monitored. This chapter gives an overview of various types of test facilities in the world and their main features in terms of experimental opportunities. It then presents typical technical equipment and sensor technologies used in laboratory environments. Finally, questions on appropriate laboratory design and experimental set-ups are discussed. One conclusion is that, in spite of many advantages, there are limits to investigating occupant behavior in a laboratory’s “artificial” environment, in part due to the fact that subjects always feel observed to some extent. However, valuable results can be achieved if the specific opportunities of laboratories are utilized both by appropriate design and precise experiments during operation.

Occupancy and Occupants’ Actions

Occupants’ presence and actions within the built environment are crucial aspects related to understanding variations in energy use. Within this chapter, first, a nomenclature for the field of research dealing with occupants in buildings is defined. This nomenclature distinguishes between occupants’ presence and behavior, states and actions, adaptive triggers, non-adaptive triggers, and contextual factors. Second, an extensive list of occupant behaviors is provided and categorizations of occupants’ actions are introduced. The list includes most of the possible phenomena that researchers may wish to study, measure, and ultimately model. The categories are physiological, individual, environmental, and spatial adjustments. Third, a list of adaptive and non-adaptive triggers together with contextual factors that could influence occupant behavior is presented. Individual elements are further grouped into physical environmental, physiological, psychological, and social aspects. Finally, a comprehensive table of studies related to occupant behavior and the corresponding significant and non-significant predictors, based on an extensive literature review, is shown. This table highlights areas of research where numerous studies have been conducted, as well as areas where hardly any research has been published. The conclusion highlights the importance of publishing future occupant monitoring campaigns with sufficient detail to inform future researchers and save redundant effort. Such detail is especially necessary in relation to the methodology, including, for example, a clear description of the type of variables monitored, and in relation to the results, where both the influencing factors that were found to be significant and insignificant should be documented.

Evaluating the performance of thermal sensation prediction with a biophysical model

Neutral thermal sensation is expected for a human body in heat balance in near-steady-state thermal environments. The physiological thermoneutral zone (TNZ) is defined as the range of operative temperatures where the body can maintain such heat balance by actively adjusting body tissue insulation, but without regulatory increases in metabolic rate or sweating. These basic principles led to the hypothesis that thermal sensation relates to the operative temperature distance from the thermoneutral centroid (dTNZop ). This hypothesis was confirmed by data from respiratory climate chamber experiments. This paper explores the potential of such biophysical model for the prediction of thermal sensation under increased contextual variance. Data (798 votes, 47 participants) from a controlled office environment were used to analyze the predictive performance of the dTNZop model. The results showed a similar relationship between dTNZop and thermal sensation between the dataset used here and the previously used dataset. The predictive performance had the same magnitude as that of the PMV model; however, potential benefits of using a biophysical model are discussed. In conclusion, these findings confirm the potential of the biophysical model with regard to the understanding and prediction of human thermal sensation. Further work remains to make benefit of its full potential.