1,721,002 research outputs found
Assessing Overall Indoor Environmental Comfort and Satisfaction: Evaluation of a Questionnaire Proposal by Means of Statistical Analysis of Responses
No full textConsidering all aspects of indoor environmental comfort (thermal, visual, acoustical and air quality) and their interactions, questionnaires aiming at detecting assess people's perception of indoor environmental quality (IEQ), well-being and satisfaction should be designed in a more homogeneous way. In particular, the choice of the questions, response options and scales adopted must satisfy consistency criteria between different IEQ areas, but also allow a direct correlation to specific measurable quantities. In this work, the design of a comprehensive questionnaire is presented for assessment of overall IEQ in educational buildings. Its ability to effectively describe users' sensation, preference, comfort and satisfaction for all four IEQ domains (thermal, visual, acoustic and air quality) is evaluated in terms of effectiveness, efficiency and resolution, using experiments and statistical analysis. The analysis shows the agreement of mean votes with environmental parameters, correlations between sensation, comfort, satisfaction in each IEQ domain, and the relationship between scales and distributions of votes in each domain
Evaluation of thermal satisfaction scales through the analysis of sensation and preference votes
No full textIn this work, the analysis of thermal satisfaction votes expressed by students during regular classes was conducted to point
out (i) the capability of predicting satisfaction votes starting from sensation and preference votes and (ii) the correspondence
between two evaluation scales which are commonly used in the assessment of satisfaction. An experimental campaign in 50
classrooms in central Italy was carried out between 2020 and 2022 through the administration of questionnaires while
monitoring indoor environmental data. Questions about thermal sensation, preference and satisfaction were addressed.
While a 7-point-scale was used for thermal sensation and preference (-3 to +3), satisfaction was investigated using a 4-point,
one-pole-scale (0 to 3) as well as a dichotomic scale (0 to 1), with 0 as “satisfied” in both cases. First, classification trees
were used to train a model having thermal sensation and preference votes as independent variables, and satisfaction
expressed in the dichotomic scale as the dependent variable. The model was rendered as a two-entry color-coded matrix to
map the probability of satisfaction votes starting from given sensation and preference votes. Then, such model was used to
predict dichotomic satisfaction for the samples in which satisfaction vote was cast on the 4-point-scale. The comparison
between the predicted (0 to 1) and the observed (0 to 3) satisfaction votes highlighted that the “1” votes expressed in the 4-
point-scale correspond in 62% of the cases with thermal satisfaction. This is somewhat not consistent with the definition of
the scale, that assumes the 0 pole as absence of attribute, and the remaining votes as gradient degrees of dissatisfaction.
Extensions of this work will focus on (i) including environmental conditions as confounding factors (ii) extending such
analysis to the IAQ, visual and acoustic domains
Thermal perception and satisfaction of Italian students in distance (home) learning vs face-to-face learning environments during the heating season
Full text linkDuring the 2020-2021 COVID-19 pandemic situation, millions of high school students in Italy had to adapt a room in their home for partial distance learning. This paper investigates the thermal perception and satisfaction with the thermal conditions expressed by 45 teenage students alternating between Distance Learning (DL) and Face-to-face learning (FL) during that period. Students completed questionnaires about their perception and satisfaction with the thermal environment while air temperature and humidity were monitored for 14 weeks. The thermal conditions in the classrooms, where students attended classes every other day, were also monitored during this time. The results show that students at home experienced a high percentage of time with conditions outside recommended comfort limits. Nevertheless, most of the students expressed a TSV equal to 0. In addition, the proposed long-term thermal discomfort indicators, such as running mean of the indoor air temperature, correlated rather poorly with subjective votes. This may indicate that different indices should be considered when analyzing mid-term subjective thermal comfort evaluations
Within- and cross-domain effects of environmental factors on students’ perception in educational buildings
No full textStudents in classrooms are exposed to environmental stimuli in the thermal, visual, acoustic and air quality domains, which affect their overall comfort and performance. Therefore, in recent studies, questionnaires are used to collect information about subjective perceptions and investigate links with physical parameters. Most field studies in educational buildings either focus on a single comfort domain, or consider multiple domains but provide inconsistent questions among the 4 domains (i.e., IAQ, thermal, visual and acoustic). Very few studies have investigated cross-domain effects in a consistent manner, considering satisfaction, comfort and perception aspects. To address this research gap, a survey with consistent questions among the 4 comfort domains was designed and used to collect more than 900 subjective responses from students. The analysis of subjective data together with objective measurements allows: (i) correlating the environmental physical parameters and students' perception in each of the comfort domains; (ii) understanding the students' preferred environmental conditions; and (iii) understanding cross-domain effects, i.e., the effects between the average conditions and the mean vote expressed for another domain. The results show that air temperature, illuminance and sound pressure level are correlated with the sensation in the respective domains, in contrast to CO2 concentration. Regarding cross-effects, the study confirms interference of CO2 concentration and illuminance on thermal sensation as well as the effect of sound pressure level on visual sensation
Understanding the Effects of Environmental Factors on Human Perception by Means of Surveys and in Field Measurements
No full textThe discomfort prediction inside buildings by means of correlations able to estimate people subjective response from indoor conditions has been widely investigated with the purpose of supporting design, commissioning and operation of buildings. Technical standards have been developed based on these findings, suggesting or prescribing acceptability ranges for the different environmental quantities involved mainly in single comfort aspects. However, buildings' occupants are not exposed to one environmental factor at a time, but to acoustical, thermal, visual, and air quality stimuli simultaneously so that the overall effect of the indoor environment on human perception and performance depends on their combined effect. Some researchers have investigated these aspects by means of laboratory studies, while few ones have conducted with field studies. Even if lab environments allow the full control of the environmental parameters, the research in real buildings has the advantage of capturing the response of people in an everyday context, while they are involved in their real activity. Among all different building types, in the educational ones the indoor factors can critically affect students' concentration and ability to learn, so that they are worth investigating. The main aim of this paper is to present results from field subjective surveys and measurements carried out in university and high school classrooms to find the crossed effects and interaction effects of different environmental factors on human perception and comfort
Comfort and energy performance analysis of different glazing systems coupled with three shading control strategies
No full textShading control strategies are often required to optimize the balance between solar gains, daylight availability, glare protection, and view to the outside. Automated shading operation, when properly designed, may avoid performance losses due to manual operation while maintaining indoor environmental comfort. In this work, the integrated performance of different glazing systems coupled with three control approaches for roller shades is presented for a typical office space. The first control is a standard open–closed operation based on a workplane illuminance range, while the other two are able to set intermediate shade positions according to the solar position to maximize daylighting. The third control addresses excessive daylight on the workplane by imposing a workplane illuminance threshold to reduce the risk of daylight discomfort glare. Daysim, based on Radiance and the daylight coefficient method, was used to calculate the annual illuminance profile over the workplane, and Evalglare was used to calculate glare indexes. EnergyPlus was used for thermal comfort and energy analysis. The results were processed through aMATLAB code for transferring required information from one tool to another. Moreover, to assess the global performance of the shading controls and fenestration configurations studied, visual and thermal comfort were evaluated through a set of metrics able to express both the availability (the fraction of time with acceptable comfort conditions at specific positions) and the spatial usability (the fraction of space simultaneously within comfort range at specific moments). The energy performance was also quantified in terms of primary energy demand for heating, cooling, and lighting. The results showed that it is possible to balance daylighting, thermal and visual comfort, and energy use. This can be achieved by simultaneously selecting shading controls that allow adequate daylight without causing glare, and glazing properties with good thermal performance that allow adequate daylight (high visible transmittance) but limit solar gains (lower solar transmittance or solar heat gain coefficient [SHGC]) for moderate and cooling-dominated climates
Model-based shading and lighting controls considering visual comfort and lighting energy use
No full textFenestration properties and controls affect energy use and comfort conditions in building perimeter zones. Dynamic façades with high performance glazing and automated shading have the potential to balance daylighting needs, comfort and energy use, when integrated with lighting and thermal systems controls. Recent efforts on developing efficient shading control strategies mainly focused on either providing more daylight to reduce lighting energy use, preventing glare, or controlling solar gains to reduce cooling requirements. Usually, this requires different sensors and control systems for shading, lighting and air-conditioning operation. This Thesis presents the development and implementation of a model-based control algorithm for automated shading and lighting operation, aiming at minimizing energy use while reducing the risk of glare. A detailed lighting model is used to compute real-time interior lighting conditions, energy use and daylight glare probability, based on the readings of two sensors on every building façade. The model, validated with full-scale experiments, is able to predict the performance of dynamic façades with complex fenestration systems and employs a hybrid ray tracing and radiosity method for lighting simulation and a detailed daylight glare module based on DGP. The model-based operation ensures optimal shade position and light dimming levels that minimize energy use while satisfying glare constraints at each time step. The developed algorithm is demonstrated in a full-scale office space, controlling shades and electric lighting through the real-time model-based optimizer, using simple sensor readings as inputs. The results show the performance of the optimized controls in terms of energy use, visual comfort and daylight provision, leading to integrated, smart façade controls for perimeter building zones
Daylighting and energy analysis of perimeter spaces with dynamic shading
No full textIn this work, a building façade is not treated as a single building component, but as a part of building perimeter zones, which may also include controllable electric lighting, shading attachments, HVAC components and indoor environmental parameters. Consequently, façade design becomes part of perimeter zone design, and the objective is to balance the need for daylighting and view versus the need of controlling of solar gains and maintaining human comfort, while at the same time minimizing energy use for air-conditioning and lighting. First, a flexible dynamic daylighting and thermal simulation model was developed, applicable to perimeter spaces with one or several exterior facades equipped with automated interior roller shades (the most common type of shading used in commercial buildings). The model accepts various fenestration properties as inputs, and provides several daylighting, thermal and electric lighting control options. Outputs of the model include the most advanced daylighting metrics, thermal loads, surface and air temperatures and energy consumption for every calculation step -as well as annual indices. Thermal and lighting results were presented for a variety of different envelope options and climates with recommendations for different orientations. It was found that windows occupying 30–50% of the facade can actually result in lower total energy consumption for most cases with simple shading controls, depending on glazing properties. New, innovative and practical shading control methods were developed for maximizing daylight utilization and minimizing building energy consumption. The new control strategies were simulated using the developed integrated model to investigate their impact on outdoor view, daylighting metrics, thermal loads and energy consumption as well as on excessive illuminance that can cause visual discomfort. For the first time, model-based control of shading devices, demonstrated in a comparative way, allowed selection of orientation-dependent control strategies and use of alternate control criteria. At the same time, the interplay between lighting energy use, solar and internal heat gains was studied considering dynamic façade systems in an integrated manner. Experimental studies were conducted to assess the impact of façade design options and related controls and to validate the developed models. Two identical full-scale office spaces with reconfigurable façade and lighting systems were designed and built for this purpose. The rooms were full instrumented with lighting and thermal sensors and equipped with automated interior roller shades and dimmable lighting systems that can be controlled according to the new developed strategies. Shading devices with different properties and different controls were tested extensively to quantify the impact of façade and lighting controls on interior conditions and energy use. A global uncertainty and sensitivity analysis was performed using the integrated model, to identify the most important factors with respect to building thermal and daylighting performance. The uncertainty analysis is based on the Monte Carlo method with Latin Hypercube Sampling, showing the possible ranges in performance indices. The sensitivity analysis uses a variance-based method in the extended FAST implementation. Application of the analysis to perimeter private office spaces showed the first order and total order effects of each studied parameter. Finally, a state-of-the-art tool with a powerful engine and a simplified interface was developed to assess the overall impact of dynamic façade elements and perimeter zone performance. It is intended to provide guidelines and quick feedback to both building design professionals and non-experts and to promote the use of efficient façade controls in the buildings community. (Abstract shortened by UMI.
Evaluating the performance of passive chilled beams with respect to energy efficiency and thermal comfort
Full text linkExisting modeling approaches for passive chilled beams determined from tests on individual chilled beams in a laboratory are not adequate for assessing overall energy usage and occupant comfort within building simulation programs. In addition, design guidelines for passive chilled beam systems are needed for identifying appropriate applications and optimal configurations. This thesis includes (i) extensive experimental studies for characterizing the performance of passive chilled beams, in both laboratory settings and in field studies, (ii) development of passive chilled beam performance prediction models, (iii) integration of these models into building simulation models/tools and (iv) use of building simulation for overall assessment of different passive chilled beam system configurations in different climates in order to provide guidelines for appropriate applications. Experiments were conducted with a single passive chilled beam in a laboratory setting and with multiple passive chilled beams installed in a real occupied office space. Based on the experimental results, models that can predict total cooling capacity and chilled surface temperature of passive chilled beams were developed. These models use essential operating conditions of the system and thermal conditions in the environment as inputs and are able to predict the energy and thermal comfort performances of the passive chilled beam system when integrated into a system simulation. The validity of using a model developed from laboratory tests on a single passive chilled beam in a system simulation for spaces with multiple chilled beams was evaluated. Comparison of laboratory and field measurements indicates that the conventional method of predicting total cooling capacity of a passive chilled beam from laboratory measurements underestimates its performance when installed in a system. These differences could have an important impact on system sizing and commissioning. Side-by-side field measurements were conducted to compare energy and comfort performance of a passive chilled beam system against constant and variable air volume systems for nearly identical office spaces. While maintaining very similar thermal comfort levels in the two offices, the passive chilled beam system led to a 57% reduction in electric energy compared to the constant air volume system. However, the variable air volume (VAV) system consumed 21% less energy compared to the passive chilled beam system during the field measurements. This is mostly because of the current configuration of the passive chilled beam system which represents the worst case scenario in terms of system configuration. The parallel air system used in the field measurement is a typical air system including the outdoor air and return air damper system. As a starting point followed by various configurations assessment with computer simulations, the return air damper was closed during the entire field measurements of the passive chilled beam system. In order to consider more realistic energy savings compared to VAV systems, alternative passive chilled beam configurations were evaluated using a system simulation model that was validated with the available measurements. The integrated simulation tool was developed and validated for the case study office space and was then used to perform comprehensive comparisons of alternative passive chilled beam and conventional systems in order to evaluate savings potential in various climatic zones. While maintaining the same thermal environments in spaces, the best passive chilled beam configuration provided electrical energy savings up to 24% for hot and humid climates and up to 35% savings for hot and dry climates compared to a variable air volume system. The radiation cooling effects of passive chilled beams were also analyzed through experiments and simulations. Both experiments and computer simulations revealed that the effect of the radiation cooling of passive chilled beams is not significant in terms of energy savings and thermal comfort improvement. Based on simulation results covering various passive chilled beam system configurations and climatic zones, the percentage of radiation cooling energy relative to total passive chilled beam cooling energy varied between 7 to 15%
An Adaptive Personalized Daylighting Control Approach for Optimal Visual Satisfaction and Lighting Energy use in Offices
No full textIn perimeter building zones with glass façades, controllable fenestration (daylighting/shading) and electric lighting systems are used as comfort delivery systems under dynamic weather conditions, and their operation affects daylight provision, outside view, lighting energy use, as well as overall occupant satisfaction with the visual environment. A well-designed daylighting and lighting control should be able to achieve high level of satisfaction while minimizing lighting energy consumption. Existing daylighting control studies focus on minimizing energy use with general visual comfort constraints, when adaptive and personalized controls are needed in high performance office buildings. Therefore, reliable and efficient models and methods for learning occupants’ personalized visual preference or satisfaction are required, and the development of optimal daylighting controls requires integrated considerations of visual preference/satisfaction and energy use.In this Dissertation, a novel method is presented first for developing personalized visual satisfaction profiles in daylit offices using Bayesian inference. Unlike previous studies based on action data, a set of experiments with human subjects was designed and conducted to collect comparative visual preference data (by changing visual conditions) in private offices. A probit model structure was adopted to connect the comparative preference with a latent satisfaction utility model, assumed in the form of a parametrized Gaussian bell function. The distinct visual satisfaction models were then inferred using Bayesian approach with preference data. The posterior estimations of model parameters, and inferred satisfaction utility functions were investigated and compared, with results reflecting the different overall visual preference characteristics discovered for each person.Second, we present an online visual preference elicitation learning framework for efficiently learning and eliciting occupants’ visual preference profiles and hidden satisfaction utilities. Another set of experiments with human subjects was conducted to implement the proposed learning algorithm in order to validate the feasibility of the method. A combination of Thompson sampling and pure exploration (uncertainty learning) methods was used to balance exploration and exploitation when targeting the near-maximum area of utility during the learning process. Distinctive visual preference profiles of 13 subjects were learned under different weather conditions, demonstrating the feasibility of the learning framework. Entropy of the distribution of the most preferred visual condition is computed for each learned preference profile to quantify the certainty. Learning speed varies with subjects, but using a single variable model (vertical illuminance on the eye), most subjects could be learned to an acceptable certainty level within one day of stable weather, which shows the efficiency of the method (learning outcomes).Finally, a personalized shading control framework is developed to maximize occupant satisfaction while minimizing lighting energy use in daylit offices with roller shades. An integrated lighting-daylighting simulation model is used to predict lighting energy use while it also provides inputs for computing personalized visual preference profiles, previously developed using Bayesian inference from comparative preference data. The satisfaction utility and the predicted lighting energy use are then used to form an optimization framework. We demonstrate the results of: (i) a single objective formulation, where the satisfaction utility is simply used as a constraint to when minimizing lighting energy use and (ii) a multi-objective optimization scheme, where the satisfaction utility and predicted lighting energy use are formulated as parallel objectives. Unlike previous studies, we present a novel way to apply the MOO without assigning arbitrary weights to objectives: allowing occupants to be the final decision makers in real-time balancing between their personalized visual satisfaction and energy use considerations, within dynamic hidden optimal bounds – through a simple interface
- …
