Indoor Environmental Quality Measurements Research Articles

Predicting thermal satisfaction as a function of indoor CO[formula omitted] levels: Bayesian modelling of new field data

In the pursuit of mitigating the performance gap between model-predicted thermal comfort and measurements of perceived thermal comfort, recent studies have investigated the multi-domain nature of thermal comfort and IEQ. This paper presents an update to a recent work that applied Bayesian logistic regression to examine possible independent correlations between perceived thermal comfort of building occupants and metrics of indoor environmental quality (IEQ) such as CO2 concentrations. The prior work made use of the COPE dataset, a 20-year-old field database of objective and subjective IEQ measurements collected from approximately 800 occupants of open-plan offices in large Canadian and US cities. This study updates that work with a new IEQ field study of 141 workstations carried out at the University of British Columbia across 2019 and 2020. In addition, a new, hierarchical (multi-level) Bayesian logistic regression model is formulated and applied. The new results not only increase the credibility of observing measurements of CO2 concentrations to improve predictions of thermal satisfaction in the original COPE dataset, but that the credibility of this evidence is strengthened on the addition of the new data. At indoor temperatures of 23.5 °C, the probability of an occupant feeling thermally satisfied at measured CO2 levels of 550 ppm was 0.62 [0.54 - 0.69, 95% CrI]. This decreased to 0.28 [0.17-0.42, 95% CrI] at 750 ppm.This study does not suggest these observations are generalizable outside the COPE and UBC datasets, nor does it suggest that CO2 must be affecting occupants physiologically or psychologically to cause these observations. However, it is suggested that CO2 levels may remain overlooked as a contextual, or latent variable for the real-time prediction of perceived thermal comfort in buildings. For instance, prior research has observed a relationship between indoor CO2 levels and perceived air quality as well as a relationship between multiple perceptual factors of IEQ, such as air quality and thermal comfort. If the findings of this paper continue to be found in future studies, measurements of CO2 concentrations may be used to improve the accuracy of thermal comfort prediction models. The core recommendation for future work is therefore to expand measurements in future thermal comfort field studies to include, at least, measurements of indoor CO2 levels. A greater dataset is needed to determine whether the findings of this study are possibly universally applicable, and/or whether knowledge of indoor CO2 concentrations may improve personalized models of thermal comfort that are building- and context-specific.

Correlations between thermal satisfaction and non-thermal conditions of indoor environmental quality: Bayesian inference of a field study of offices

The judgment of thermal comfort is a cognitive process influenced by physical, psychological and other factors. Prior studies have suggested that occupants who are generally satisfied with many non-thermal conditions of indoor environmental quality (IEQ) are also more likely to be satisfied with thermal conditions as well. This paper applies Bayesian logistic regression to identify and predict the independent relationship between non-thermal metrics of IEQ, such as CO2 concentrations, noise levels, and light levels, and perceived thermal comfort. The study is the first to do so with respect to a large field study. The regression analysis is done against a dataset of objective and subjective IEQ measurements collected from 779 occupants of open-plan offices in large Canadian and US cities. The results suggest there is evidence supporting a view that measurements of indoor CO2 concentrations and indoor speech intelligibility are correlated with perceived thermal satisfaction. For example, a posteriori predictions drawn from the regression model suggest that, under the same psychrometric conditions (i.e., operative temperature = 23 °C, relative humidity = 30%, etc.), occupants experiencing indoor CO2 concentrations of 500 ppm were ~30 ± 8% more likely to state they felt thermally satisfied than occupants experiencing indoor conditions at 900 ppm.

IEQ Field Investigation in High-Performance, Urban Elementary Schools

School buildings are one of the most commonly occupied building types for children, second only to their homes. Indoor environmental quality (IEQ) is an ongoing issue in schools, especially in urban environments where students are exposed to higher levels of outdoor pollutants. To examine this issue, five elementary school buildings located in a major city on the East Coast of the United States were selected for one-week of quantitative IEQ measurements, with a satisfaction survey collected from teachers at the selected schools. The schools included three high-performance schools, one recently renovated school, and one conventional school. Despite building designers and operators following the recommendations of current high-performance design standards, the three high-performance school buildings did not have measurably better IEQ than the renovated and conventional school buildings, nor were they perceived as better based on the satisfaction survey. This indicates that current high-performance design standards may not place enough emphasis on reducing health-related pollutants in urban schools.

The Spatial and Temporal Variability of the Indoor Environmental Quality during Three Simulated Office Studies at a Living Lab

The living lab approach to building science research provides the ability to accurately monitor occupants and their environment and use the resulting data to evaluate the impact that various components of the built environment have on human comfort, health, and well-being. A hypothesized benefit of the living lab approach is the ability to simulate the real indoor environment in an experimentally controlled setting over relatively long periods of time, overcoming a significant hurdle encountered in many chamber-type experimental designs that rarely reflect typical indoor environments. Here, we present indoor environmental quality measurements from a network of sensors as well as building system design and operational data demonstrating the ability of a living lab to realistically simulate a wide range of environmental conditions in an office setting by varying air temperature, lighting, façade control, and sound masking in a series of three human subject experiments. The temporal variability of thermal and lighting conditions was assessed on an hourly basis and demonstrated the significant impact of façade design and control on desk-level measurements of both factors. Additional factors, such as desk layout and building system design (e.g., luminaires, speaker system), also contributed significantly to spatial variability in air temperature, lighting, and sound masking exposures, and this variability was reduced in latter experiments by optimizing desk layout and building system design. While ecologically valid experimental conditions are possible with a living lab, a compromise between realism and consistency in participant experience must often be found by, for example, using an atypical desk layout to reduce spatial variability in natural light exposure. Based on the experiences from these three studies, experimental design and environmental monitoring considerations for future office-based living lab experiments are explored.

Post-Occupancy Evaluation and IEQ Measurements from 64 Office Buildings: Critical Factors and Thresholds for User Satisfaction on Thermal Quality

The indoor environmental quality (IEQ) of buildings can have a strong influence on occupants’ comfort, productivity, and health. Post-occupancy evaluation (POE) is necessary in assessing the IEQ of the built environment, and it typically relies on the subjective surveys of thermal quality, air quality, visual quality, and acoustic quality. In this research, we expanded POE to include both objective IEQ measurements and the technical attributes of building systems (TABS) that may affect indoor environment and user satisfaction. The suite of three tools, including user satisfaction survey, workstation IEQ measurements, and TABS in the National Environmental Assessment Toolkit (NEAT) has been deployed in 1601 workstations in 64 office buildings, generating a rich database for statistical evaluation of possible correlations between the physical attributes of workstations, environmental conditions, and user satisfaction. Multivariate regression and multiple correlation coefficient statistical analysis revealed the relationship between measured and perceived IEQ indices, interdependencies between IEQ indices, and other satisfaction variables of significance. The results showed that overall, 55% of occupants responded as “satisfied” or “neutral”, and 45% reported being “dissatisfied” in their thermal quality. Given the dataset, air temperature in work area, size of thermal zone, window quality, level of temperature control, and radiant temperature asymmetry with façade are the critical factors for thermal quality satisfaction in the field. As a result, the outcome of this research contributes to identifying correlations between occupant satisfaction, measured data, and technical attributes of building systems. The presented integrated IEQ assessment method can further afford robust predictions of building performance against metrics and guidelines for IEQ standards to capture revised IEQ thresholds that impact building occupants’ satisfaction.

Minimizing the energy consumption of low income multiple housing using a holistic approach

The present paper describes a holistic energy efficient retrofit of low income multiple social housing located in Athens, Greece. A holistic analysis was conducted in order to determine the optimum retrofit plan that includes innovative and state of the art commercially available technologies, passive techniques as well as renewable energy sources, aiming to reduce its energy consumption and carbon footprint, improve indoor environmental conditions and be cost effective at the same time. An extensive experimental campaign including air leakage measurements, thermal imaging, energy consumption and indoor environmental quality measurements was conducted before and after the implementation of the retrofit. In addition, advanced building simulation, occupant surveys and socioeconomic analyses were performed in order to evaluate the impact of the retrofit and estimate specific performance indicators.

Impacts of human and spatial factors on user satisfaction in office environments

Post Occupancy Evaluation (POE), as an architectural design decision tool, utilizes data concerning multiple users' satisfaction in conjunction with indoor environmental components to develop a better quality of human life. However, one of the limitations of POE that is frequently pointed out is its excessive reliance on surveys and general solutions, without a full understanding of the occupants' physiological characteristics and pertinent environmental performance/conditions. This lack of awareness may lead to irrelevant modifications and the occupants' dissatisfaction with indoor environmental quality (IEQ). Therefore, this study suggested an integrated POE, that combined a quantifiable environmental dataset to indicate each individual occupant's satisfaction with each IEQ element. At 411 workstations in modern offices located in Southern California of the U.S., on-site IEQ measurements and user satisfaction surveys were conducted. Statistical analyses of the collected data were also conducted within specific categories of building types, spatial attributes, and human factors. These analyses revealed significant relationships that exist between human factors and IEQ satisfaction, as well as environmental conditions, including gender, age, workstation location, etc. These relationships could be ranked in accordance with the impact that sensitivities of individual IEQ elements using a decision tree algorithm, have on human physiological conditions. These findings suggested a hierarchical approach as an optimal design solution to maximize the occupants' well-being in their workplace environments. Therefore, these results reinforced the necessity for an integrated POE with consideration of human and environmental factors in order to provide enhanced/optimal IEQ design solutions for specifically-targeted population and spatial conditions.

Performance validation case study: Federal office building with an integrated facade

The General Services Administration Edith Green Wendell Wyatt building has undergone an extensive retrofit and is distinguished by its new integrated facade.1 It has been transformed from a poorly performing office building into a highly efficient Leadership in Energy and Environmental Design (LEED) Platinum facility. The unitized curtain wall includes fixed exterior shading tuned for each solar orientation. The new interior environment optimizes daylight and electric lighting, thermal comfort, and air quality. This article reports on post-occupancy evaluations to validate and fine-tune the performance of Edith Green Wendell Wyatt building. The focus is on post-occupancy evaluation studies that relate to the integrated facades. Overall, post-occupancy evaluations address three categories: (1) resource use and generation—energy and water, (2) occupant satisfaction, and (3) indoor environmental quality measurements. During design, the impact of building enclosure measures and internal loads was linked directly to the selection of the mechanical system. The team determined that strategic use of glazing and exterior shading would support highly efficient hydronic radiant heating and cooling. Post-occupancy evaluation methods include installed data sources (from the building management system and other installed measurement and verification systems) and proposed field testing. Occupant satisfaction has been evaluated with an on-line survey from the Center for the Built Environment. The results have been filtered by solar orientation, floor, and other criteria to understand the facades’ impact on occupant satisfaction. Pre-occupancy results and additional benchmarking compare the results with government and other general office buildings. As of January 2015, many of the post-occupancy evaluation studies have been completed, but some are still on-going. Post-occupancy evaluation objectives include: demonstrating federal energy compliance, refining building performance, and providing feedback for future work.

Indoor Air Quality Survey of Nail Salons in Boston

Employees in nail salons, largely Vietnamese immigrant women in Boston, are exposed to a range of volatile organic chemicals from the products used in salons, including solvents, glues and polishes. Some of these chemicals have the potential to cause short and long-term adverse health effects. Only limited research has been performed on assessing occupational exposures. This project aimed to characterize total volatile organic compound (TVOC) and PM2.5 concentrations in nail salons as a function of ventilation, building characteristics, customer and employee occupancy, and type of services being performed. Students conducted sampling in 21 salons in Boston, MA from September to December, 2011. Study visits included: indoor environmental quality measurements (TVOCs, PM2.5 and carbon dioxide), site observations, and an interview. CO2 levels in 15 of 21 salons exceeded 800 ppm, suggesting that these salons may have insufficient ventilation. Higher TVOC and PM2.5 levels were found in salons with less ventilation (as estimated using CO2 concentrations). Contrary to our a priori hypothesis, average levels of TVOCs, CO2 and PM2.5 were consistent throughout salons, indicating that exposures may not be restricted to areas in the salon where work is being performed (e.g., at the manicure table). Higher TVOC concentrations were observed when tasks were being performed, yet were not dependent upon the number of tasks being performed. Improving ventilation conditions in salons to meet minimum outdoor air delivery requirements can reduce exposures to TVOCs.

Novel second-degree solution to single zone mass-balance equation improves the use of build-up data in estimating ventilation rates in classrooms

Recent advances in international guidelines for indoor air quality and on-going work on guidelines for ventilation in Europe increase the need for routinely applicable measurement methods for indoor air quality and ventilation. Ventilation is the key determinant of the behaviour of pollution from both indoors and outdoors in buildings and therefore should be measured together with other indicators of indoor air quality. Various methods have been proposed to measure ventilation rates in different types of buildings. Utilizing carbon dioxide as a marker substance and applying several ventilation phase-based methods together allows for recognizing air recirculation and quantifying CO 2 emission levels that have been identified as challenges in CO 2 -based methods, as well estimating the intrinsic variability of ventilation rates over various levels of occupancy. In schools CO 2 based estimation of ventilation has often been applied to decay phase only, which is not representative of exposure of the school children while using time periods when the classroom is not occupied and when the ventilation may be enhanced, e.g., by opening windows. This paper presents a novel solution to the mass-balance equation facilitating the use of the build-up phase to solve air exchange rates. The new equation allows to avoid impacts of device calibration errors and in combination with previously used steady state and decay methods improves significantly representativity of ventilation estimates in schools. Practical implications Combined use of occupancy phase based ventilation assessment method improves the quality of CO 2 -based estimates of ventilation alone and as part of more comprehensive indoor environmental quality measurements.