• Energy Research

We present a method that can be used to optimize CFD analyses of ventilation performance in buildings; the method was successfully applied in other disciplines. In the method, three statistical methods are used - the Taguchi method, ANOVA, and Grey Relational Analysis (GRA) to achieve optimization. We then model the risk of draft and the mean age of air in a two-dimensional benchmark test case to exemplify the application of the method. We use five independent variables for modeling: temperature, air velocity, and three room dimensions, each with five levels. In short, the method is implemented as follows: At first, using an L25 orthogonal array in the Taguchi method, we decreased the total number of cases to be modeled from 3125 (5 5) to 25. Then, we modeled the 25 cases with CFD and used the Taguchi method and ANOVA analyses to find the best solutions for draught risk or the age of air, while with the GRA method we found the best solution for both of them considered jointly. Finally, new CFD models for the variables describing the best solutions were run to confirm their superiority within the 25 cases selected for modeling within the orthogonal L25 array. They were not compared against all possible 3125 cases because the computational time would have been prohibitive. Nevertheless, we believe, that the results are credible in identifying the best solutions. This is based on experience in other disciplines. We, therefore, propose that the presented method is considered when complex problems are analyzed related to ventilation performance requiring large computational power.

Abstract The effects on human performance of elevated temperature causing thermal discomfort were investigated. Recruited subjects performed neurobehavioural tests examining different component skills, and addition and typing tasks that were used to replicate office work. The results show that thermal discomfort caused by elevated air temperature had a negative effect on performance. A quantitative relationship was established between thermal sensation votes and task performance. It can be used for economic calculations pertaining to building design and operation when occupant productivity is considered. The relationship indicates that optimum performance can be achieved slightly below neutral, while thermal discomfort (feeling too warm or too cold) leads to reduced performance. Consequently, it makes sense to set the PMV limits in workplaces in the range between −0.5 and 0 instead of between −0.5 and 0.5 as stipulated in the present standards.

Indoor environments have a large impact on health and well-being, so it is important to understand what makes them healthy and sustainable. There is substantial knowledge on individual factors and their effects, though understanding how factors interact and what role occupants play in these interactions (both causative and receptive) is lacking. We aimed to: (i) explore interactions between factors and potential risks if these are not considered from holistic perspective; and (ii) identify components needed to advance research on indoor environments. The paper is based on collaboration between researchers from disciplines covering technical, behavioural, and medical perspectives. Outcomes were identified through literature reviews, discussions and workshops with invited experts and representatives from various stakeholder groups. Four themes emerged and were discussed with an emphasis on occupant health: (a) the bio-psycho-social aspects of health; (b) interaction between occupants, buildings and indoor environment; (c) climate change and its impact on indoor environment quality, thermal comfort and health; and (d) energy efficiency measures and indoor environment. To advance the relevant research, the indoor environment must be considered a dynamic and complex system with multiple interactions. This calls for a transdisciplinary and holistic approach and effective collaboration with various stakeholders.

Abstract This paper is an overall summary of research by the authors on how classroom conditions affect the performance of schoolwork by children, motivated by the fact that the thermal and air quality conditions in school classrooms are now almost universally worse than the relevant standards and building codes stipulate that they should be. This is sometimes because financial resources for the maintenance and upgrade of school buildings are inadequate, but it is also because schools are increasingly allowing classroom temperatures to drift above the recommended range of 20–22 °C in warm weather and allowing outdoor air supply rates to remain so low that carbon dioxide (CO 2 ) levels during school hours exceed 1000 ppm for long periods, in order to conserve energy. The research that is summarized in this paper shows that the indoor environmental consequences of either of these investment-free but ill-advised energy conservation measures can reduce children's performance of schoolwork by as much as 30%, so a more sophisticated approach to maintaining good classroom indoor environmental quality (IEQ) is required.

The present study investigated indoor climate and window opening behaviour by pupils, as well as their perceptions and symptoms in classrooms with different types of ventilation systems. Four classrooms were selected in the same school in suburban Denmark. Classroom ventilation was achieved either by manually operable windows, or by automatically operable windows with and without an exhaust fan in operation, or by a balanced mechanical ventilation system. Indoor air temperature, relative humidity, carbon dioxide (CO2) concentration and window opening were continuously monitored for one month in non-heating and heating seasons; CO2 concentration was used to estimate average classroom ventilation rates. At the end of each measuring period, the pupils were asked to report their perceptions of the indoor environment and their acute health-related symptoms. The classroom in which ventilation was achieved by manually operable windows had the highest air temperatures and CO2 concentrations during both non-heating and heating season; the estimated average air-change rate was lowest in this classroom. The classroom with mechanical ventilation had the highest estimated average air-change rate. Windows were frequently opened in all four classrooms in the non-heating season but very seldom in the heating season. Automatic operation of the windows had a marked effect on CO2 concentration and classroom temperature in the heating season. Perceptions of the indoor environment were more positive in the classroom that was ventilated by automatically operable windows with an exhaust fan in operation: fewer symptoms were reported in this classroom compared with classrooms with other systems. Present results and approach can be used as the basis for rational selection of systems that ensure adequate classroom ventilation.

Abstract Energy conservation in buildings as a way to reduce the emission of greenhouse gases is forcing an urgent re-examination of how closely thermal and air quality conditions should be controlled in buildings. Allowing conditions to drift outside the optimum range would conserve very large amounts of energy and would in most cases have only marginal effects on health or subjective comfort. The question that then arises is whether occupant performance would be negatively affected and if so, by how much. This information is required for cost-benefit analyses. The answers in this paper are based on laboratory and field experiments that have been carried out since the massive increase in energy costs that took place in the 1970s. Although only a few of the mechanisms by which indoor environmental effects occur have been identified, it is already clear that any economies achieved by energy conservation will be greatly exceeded by the costs incurred due to decreased performance. Reducing emissions by allowing indoor environmental conditions to deteriorate would thus be so expensive that it would justify greatly increased investment in more efficient use of energy in buildings in which conditions are not allowed to deteriorate. Labour costs in buildings exceed energy costs by two orders of magnitude, and as even the thermal and air quality conditions that the majority of building occupants currently accept can be shown to reduce performance by 5–10% for adults and by 15–30% for children, we cannot afford to allow them to deteriorate still further.

Abstract This research focused on investigating thermal comfort in naturally ventilated (NV) dormitory buildings in hot summer and cold winter (HSCW) climate zone in China. A field study was conducted during the summer of 2016 in Changsha, located in HSCW climate zone. The occupants reported subjective thermal perception using questionnaires and ambient environmental variables were measured simultaneously. A total of 11 NV dormitory buildings were investigated. 467 valid sets of measurement data and subjective questionnaires were obtained. Both Griffiths and linear regression analysis showed that the neutral operative temperature (To) was 26.2 °C. The upper limit for 80% acceptability was determined as 28.5 °C. The most acceptable operative temperature was 26.6 °C. 80% of occupants were comfortable at the temperature range between 25 °C and 28.7 °C. Based on this study, the adaptive model was developed and verified. The adaptive behaviors of clothing adjustment and air velocity adjustment were closely correlated to indoor To. The functions of adaptive thermal behaviors can be used for building simulation. The results can be used to assess indoor thermal comfort in buildings, and help to build a more rigorous database for building designing.

Although indoor environmental quality (IEQ) and human health have been on the agenda of the green building industry, a new emphasis is being placed on building features that explicitly promote the experience of occupants. However, evidence of the performance of green-certified buildings from the occupant perspective remains inconsistent, with numerous questions on how to effectively design, assess and promote ‘healthy buildings’. Focusing on the key IEQ categories of indoor air quality, thermal comfort, lighting and acoustics, this paper synthesises emerging knowledge related to IEQ and health; identifies research and practical challenges that may impede the performance of green-rated buildings; sets the foundations for researchers and green rating system developers to capture immediate and long-term opportunities; and proposes a new framework for green-certified buildings. The envisioned future of green buildings will need to be based on a thorough knowledge of the building and its users, their inter- and intra-individual variability, their spatiotemporal localisation, their activities, their history of exposures, together with a capacity of anticipation of the likelihood of future events and preparedness for them. A balanced, integrated, consideration of these factors can provide the basis for more effective green building certification systems. 'Practice relevance' The Covid-19 pandemic has focused attention on the importance of IEQ and highlighted the limitations of prevailing practice for promoting human experience, health and wellbeing. Most critically, the good intentions of project planning are often not reflected in real-world conditions, and establishedbest practiceshave not kept pace with advances in research. This paper provides a critical synthesis of the literature on the effectiveness of green building ratings systems for human experience. It identifies limitations and practical opportunities for improvement in the design and application of rating tools. These observations present specific, actionable, opportunities to improve the design and operation of green building rating systems. Rating system developers and practitioners can use this information to better align design intentions with outcomes. Explicit consideration is needed for differences in individual preferences, spatial and temporal variabilities of IEQ factors, occupant exposure history, and other factors impacting IEQ.