The importance of sample grouping; Exploring thermal sensitivity of occupants within one building type and ventilation mode

Occupants’ thermal response is influenced by their sensitivity to temperature variations, i.e. the rate of change in occupants’ thermal sensation per unit change in indoor temperature. Thermal sensitivity is commonly taken as constant (Griffiths constant) in the calculation of occupants’ comfort temperature. This constant is based on small differences found between buildings’ ventilation modes [naturally ventilated (NV) vs. air conditioned (AC)]. However, recent research found significant differences depending on building type, ventilation mode, age, gender and climate. This paper reviews thermal sensitivity within the same building type and main ventilation mode using longitudinal surveys and monitoring data from school buildings, two in the UK (U1 and U2) and one in Sweden (S1). Results show that in two of the schools (U1 and S1) children were half as sensitive as in school U2 and the difference is statistically significant. A similar result with slightly different thermal sensitivities was derived from comparison by clusters derived from the classrooms’ indoor temperatures. This outcome suggests that building ventilation mode (AC/NV), which is typically considered the main determinant of occupants’ thermal experience and often the only building information recorded in field surveys, is inadequate to explain this important occupant response factor

The role of a building’s thermal properties on pupils’ thermal comfort in junior school classrooms as determined in field studies

Recent thermal comfort research in a light-weight junior school building showed that children were more sensitive to higher temperatures than adults and subsequently that current thermal comfort standards were not appropriate for the assessment of their thermal environment. This paper presents a comparison of these survey results to those from a survey conducted in a medium-weight school building, in order to evaluate the role of the construction type on the results. Both surveys followed the same methodology, including thermal comfort questionnaires and measurements of indoor environmental variables. A total of 2990 responses were gathered. The buildings had an average difference in air temperature of 2.7oC during occupied hours in the period of investigation (June and July 2012), with the medium-weight building being cooler than the light-weight building. However, the different construction type and the cooler overall thermal environment in the medium-weight school building had little impact on the pupils’ overall thermal sensitivity. The comparison showed a general agreement on the pupils’ warm thermal sensation trends, interpersonal variation and undeveloped adaptive behaviour. The results further support the finding that current thermal comfort criteria lead to an underestimation of pupils’ thermal sensation during summer

Winter thermal comfort and indoor air quality in Swedish grade school classrooms, as assessed by the children

This paper presents results from a pilot thermal comfort study in five Swedish grade school classrooms in three different buildings during winter 2015/16. The study includes measurements of environmental parameters (air temperature, globe temperature, relative humidity, air speed, CO2) and questionnaire surveys designed to match the children’s cognitive level. The questionnaire includes questions about thermal perception, air quality and air movement, as well as the children’s clothing level. The aim of this study is to investigate whether recently found differences in thermal sensation between children and adults outside the heating season also apply to the winter season. Children’s assessment is compared to the objective measurements during the surveys, to winter design criteria for school classrooms and to comfort temperatures from previous studies. The results agree with the previously found warmer sensation of children compared to adults’ predicted thermal sensation based on the currently used PMV model, although this time the difference is smaller. Regarding air quality, no relationship was found between children’s assessment and CO2 levels

The potential of the adaptive thermal comfort concept in longterm actively conditioned buildings for improved energy performance and user wellbeing

Technological progress in conditioning practice combined with prevailing thermal comfort criteria, created stable, tightly controlled indoor temperature bands. Research shows indoor temperatures to be increasing in the heating period, leading to higher building energy use than planned. Field studies provide proof that occupants not in control of their indoor climate are more dissatisfied and report problems in wellbeing. Widening temperature bands could be an effective measure leading to energy conservation, increasing satisfaction and, as shown recently, helping to mitigate health problems related to our way of life. The adaptive approach to thermal comfort postulates that people\u27s thermal comfort perception adapts to the indoor and outdoor climatic conditions they normally experience. However, according to standards, the adaptive model is applicable only to passively conditioned (free-running) buildings, even though the adaptive principles may well apply also to actively conditioned buildings. Our review found studies demonstrating positive health effects and energy conservation potential in permanently or seasonally conditioned buildings. On this basis, the potential of the adaptive approach and translations into concrete design or operation solutions for actively conditioned buildings are discussed in this paper. We conclude that the adaptive concept offers a potential for indoor climate control in actively conditioned buildings in the temperate and cold climates

Analysis of Swedish school buildings\u27 energy performance certificates with focus on ventilation systems

Energy performance certificates are valuable sources of information about buildings. They are primarily used to assess the buildings\u27 energy performance, however the data included can also be used for building stock description or analysis from different perspectives. School buildings account for a substantial part of the Swedish public building stock and represent a great opportunity for implementation of energy saving strategies. To improve the energy efficiency, it is first important to analyse and understand the current energy use and identify the key factors responsible for most of the energy use. In Sweden, data used for EPC compilation are in most cases real measured data opposite to other European countries where EPC comprises calculated data practices. Therefore, the energy performance value provides a much more realistic representation of the building energy use. This study analyses certain aspects of school buildings\u27 energy performance using data available in EPCs, such as year of construction, floor area, heat supply systems and ventilation system. Comparison with data from some other European countries is also presented. The data which could be included in the certificate to extend the potential of EPC use in other areas, such as evaluation of indoor environmental quality, is also discussed

Influence of indoor environmental quality and dwelling satisfaction aspects on overall satisfaction: Findings from a Swedish national survey

The objective of this study is to contribute to the discussion on the impact of dwelling satisfaction aspects (size, standard, layout, appearance/aesthetics, well-being, cost and area/neighbourhood) and perceived indoor environmental quality (thermal comfort, air quality, satisfaction with daylight and acoustic comfort) on occupants\u27 overall satisfaction. This article uses data from the Swedish National Survey, BETSI (2007/08). The results are representative of adults living in multi-family and single-family buildings (1597 responses/955 buildings). Linear regression models are developed with overall satisfaction as the dependent variable and independent variables: seven satisfaction aspects, four indoor environmental quality factors and all combined (eleven). An all-model explained 54.7% of the results (best performed). All the retained variables (except satisfaction with daylight) are statistically significant predictors. Satisfaction with well-being (b = 0.286) and satisfaction with dwellings\u27 standard (b = 0.188) have the greatest effect on overall satisfaction. The model with the IEQ aspects explained only 35.5% of the results. Reliability statistics (Cronbach\u27s alpha) and confirmatory factor analysis have been implemented in the dataset. The responses can be categorized into two clusters. The two clusters were significantly different across living duration, dwelling type, age category and tenure status

Indoor humidity of dwellings in a northern climate

Low indoor relative humidity has been shown to be an issue in Swedish dwellings and mostly apartments, during the heating season. Present analysis adds to the scientific literature by demonstrating a possible association between low relative humidity and particular health symptoms and complaints

Using data-driven indoor temperature setpoints in energy simulations of existing buildings: A Swedish case study

Building energy analyses of large samples or building stocks commonly use National building stock temperature averages in their calculations. However, such averages may not be representative of the conditions in a specific building type and may mask meaningful information found at building or dwelling level. Analysis of indoor temperature data from the Swedish housing stock showed that 25% out of approximately 1000 dwellings were heated at a temperature ≥23\ub0C in wintertime. If indoor temperature management is considered as a potential energy saving measure for the building stock it may be more effective to explore implementation in these specific dwellings, than considering average temperature reduction across the entire building stock. This however would require more detailed input data on indoor temperatures. Would such an approach be worthwhile? To answer this question, two types of Swedish multifamily buildings were simulated with i) business-as-usual scenarios and ii) setpoints based on indoor temperature data from the last Swedish National Survey. The study shows that using data-driven, dwelling-specific indoor temperatures could lead to more effective decision making on indoor temperature management, targeting buildings and dwellings where temperature reduction would most likely cause the least compromise on comfort. Such a strategy however should be complementary to a wider plan of improved energy efficiency measures across the building stock

Indoor humidity of dwellings and association with building characteristics, behaviors and health in a northern climate

Data from a nationwide survey on the status of the Swedish residential building stock and indoor air quality was placed in the public domain by the National Board of Housing, Building and Planning of Sweden. The current research investigates the indoor humidity conditions in Swedish residential buildings, single-family houses and apartments, assessing the measurements from the extensive BETSI-survey against adjusted relative humidity levels based on existing norms and Standards. The aim of this study is to investigate associations and correlations between relative humidity levels and multiple building and system characteristics, occupancy patterns and behaviors and health symptoms-complaints. The analysis uses 13 categorical and 9 continuous variables-parameters of the examined dwellings. Analysis shows that low indoor relative humidity is a realistic issue in Swedish dwellings during the heating season. The issue is more prevalent in apartments than single-family houses. In addition, low indoor relative humidity seems to be more extensive in dwellings with higher indoor temperature, smaller volume, higher ventilation rate and frequent airing practices, lower number of occupants, constructed mainly after 1985, in city suburbs and in the northern parts of the country. The developed multinomial logistic regression model may predict very accurately the relative humidity level of the Swedish dwellings, during heating season. This analysis offers additional evidence to the scientific literature for possible correlation of low relative humidity with specific health symptoms, complaints and disturbances

Exploring the Link between Thermal Experience and Adaptation to a New Climate

Numerous field studies conducted in different locations have found that peoples’ thermal comfort varies with local climate. However, little is understood about the effect of moving from one climate to another. Literature suggests that people would be able to adapt to the typical indoor climate in a new location, though estimated timescales for this process differ. This paper uses data from a 6-month field study to investigate the process of thermal adaptation to a new climate. The field study consisted of a series of four thermal comfort surveys conducted with 48 occupants of single occupancy residential accommodation units, which helped to estimate their preferred temperatures. The surveys were carried out between October 2015 and April 2016 in Southampton, UK, with high resolution indoor air temperature data collected for the periods between the surveys.Study participants were grouped into three categories: long term residents of the UK (Category A), recently moved to the UK from cold climates (Category An) and recently moved to the UK from warm climates (Category B). The higher indoor temperatures of participants from cool climates (Category An) indicates the influence of indoor thermal history in determining thermal comfort conditions in a new location. This is highlighted by the fact that 94% of Category An participants reported having heating in their previous residence compared to 17% of Category B participants. Analysis of comfort temperatures over the first 6 months of occupancy shows no indication that occupants from Category An or B are adapting their indoor preferences to match that of long term UK residents, given the choice to create their preferred environment. Finally, comparison of indoor air temperature and comfort temperature found a higher correlation in Category A participants which supports the key principles of adaptive comfort theory. Category An demonstrated fairly close correlation though air temperatures were higher than comfort temperatures which may be due to embedded heater use behaviour patterns. Category B demonstrated no correlation between comfort temperature and air temperature which may be due to unfamiliarity to indoor heating systems