Indoor Environmental Quality Index Research Articles

Development of indoor environmental quality index using a low-cost monitoring platform

The fundamental goal of modern high-performance buildings is to achieve low environmental carbon footprint while securing indoor conditions that promote human health and well-being. Current procedures for indoor environmental quality (IEQ) assessment are often sporadic, expensive, intrusive and often limited to few parameters and experts-use only. This research examines an overall IEQ assessment model in three field studies. The assessment of IEQ is achieved with the methodology for the integration of relevant IEQ parameters into an overall index through derivation of their individual weighting coefficients. A low-cost open-source platform “ENVIRA” was developed and deployed for continuous measurement of relevant IEQ parameters. A total of 125 occupants participated in the field studies – 69 in two open offices and 56 in the educational building. The results from occupant survey regression analysis for offices showed that indoor air quality is the most critical IEQ parameter with the weight of 0.35 followed by thermal comfort (0.285), acoustic comfort (0.195) and illumination (0.17). The occupant preference differed in the educational building where thermal comfort was the most dominant component (0.31) followed by indoor air quality and acoustics (0.25), and lighting (0.19). Results show that individual weighting coefficients are not equivalent and could differ across building types. Finally, the mean absolute error between the average survey results and the overall IEQ index for the three field studies was <3% suggesting that the platform can be used for generating large IEQ datasets for researchers and practitioners.

Implementation of the Indoor Environmental Quality (IEQ) Model for the Assessment of a Retrofitted Historical Masonry Building

Achieving a satisfactory level for indoor environments of historical buildings is an ongoing problem that needs to be solved due to a large demand for deep retrofits in the whole of Europe. The implementation of the indoor environmental quality index (IEQ) to predict an occupant’s satisfaction in thermo-modernized historical buildings is a new concept which is a response to existing needs. In this article, a relevant study is provided with the intention to evaluate the indoor environmental performance of retrofitting effects in historical buildings dating back to the years 1873–1878. Considering the historical character of the buildings, some of the cellar spaces were fitted out with an innovative internal insulation system of mineral sheets based on calcium silicate to prevent water vapor condensation and effectively limit mold growth. The IEQ methodology was applied for retrofitted and non-retrofitted spaces as a comparison. Four essential components of indoor quality are investigated: thermal comfort, indoor air quality, acoustic comfort, and visual quality. The results of sub-component indexes are calculated based on the measured indoor parameters and the specific sensory functions. This paper discusses the results of an indoor environmental analysis including a mycological air quality assessment with the newly developed IAQindex (fungal air contamination index), total volatile organic compound concentration (TVOC), CO2, and formaldehyde (HCHO) assessment, the evaluation energy-related thermal comfort, acoustic, and visual quality, of modernized spaces. A questionnaire survey study was additionally carried out among a building’s users intentioned to compare the accounts of satisfaction before and after the retrofitting process and also to compare “subjective” results with the one’s based on in situ tests. The retrofitting approach was proven to be effective in limiting the presence of molds and a significant difference in indoor environmental quality between thermally insulated and uninsulated spaces was observed and discussed.

Review of Indoor Environmental Quality Evaluation Index Based on Regional Climate Connected Green Building

This article will review and analyses the indoor environment quality indicators in the existing green building rating system, both foreign and Chinese green building standards. Based on the relevance of ‘human climate architecture’, the indoor environment quality indicators which are intuitively perceivable, health related and connected to regions and climates will be sorted out, to establish the foundation for further indoor environmental quality index classification research.

Air Enthalpy as an IAQ Indicator in Hot and Humid Environment—Experimental Evaluation

The authors studied the impact of indoor air humidity in the range of 60% to 90% on building user perception in the temperature range of 26 to 28 °C. The research thesis was put forward that the impact of humidity on indoor air quality dissatisfaction of building users in a warm and humid indoor environment is greater than that indicated in thermal comfort models. The presented experiment examined the indoor air quality perception of n = 28 subjects in the test chamber of a nearly zero energy building under ten environmental conditions, together with a thermal comfort assessment. The authors developed an experimental relation for predicting building users’ satisfaction based on the Weber–Fechner law, where the predicted percentage of dissatisfied users (PD) is determined by means of air enthalpy (h), PD = f(h). The obtained results confirmed the sated thesis. Additionally, the intersection points of the experimental function and isotherms resulting from the Fanger model are presented, where the thermal comfort assessment starts to indicate lower user dissatisfaction results than experimental values. The authors recommend the experimental equation for humid air enthalpies in the range of 50 to 90 kJ/kg. The indoor air quality assessment based on the enthalpy value is simple and can be used to determine the overall Indoor Environmental Quality index of a building (IEQindex).

Combined Model for IAQ Assessment: Part 1—Morphology of the Model and Selection of Substantial Air Quality Impact Sub-Models

Indoor air quality (IAQ) is one of the most important elements affecting a building user’s comfort and satisfaction. Currently, many methods of assessing the quality of indoor air have been described in the literature. In the authors’ opinion, the methods presented have not been collected, systematized, and organized into one multi-component model. The application purpose of the assessment is extremely important when choosing IAQ model. This article provides the state-of-the-art overview on IAQ methodology and attempts to systematize approach. Sub-models of the processes that impact indoor air quality, which can be distinguished as components of the IAQ model, are selected and presented based on sensory satisfaction functions. Subcomponents of three potential IAQ models were classified according to their application potential: IAQ quality index, IAQ comfort index, and an overall health and comfort index. The authors provide a method for using the combined IAQ index to determine the indoor environmental quality index, IEQ. In addition, the article presents a method for adjusting the weights of particular subcomponents and a practical case study which provides IAQ and IEQ model implementation for a large office building assessment (with a BREEAM rating of excellent).

Determining indoor environmental criteria weights through expert panels and surveys

ABSTRACTA growing focus on occupant comfort, health and wellbeing has resulted in attempts to quantify indoor environmental quality (IEQ) and to determine the relative contributions of single IEQ aspects to an overall IEQ index. The recently developed IV20 tool assesses potential IEQ to label overall IEQ, and assign separate scores for the main indoor environment (IE) areas: thermal, visual, acoustic and air quality. In the absence of objective, universally applicable IEQ weights, this paper develops and executes a methodology asking regional experts with different backgrounds to make relative comparisons between related IE aspects. The authors hypothesize that wide-ranging subjective evaluations can be combined into useful relative weights (best operational solution based on the current status of IE literature).This paper presents results from an IE expert survey on relative IE aspect weights using simple percentile prioritization and the Analytic Hierarchy Process pairwise comparison. Results are compared to expert panel judgements to ensure validity. The advantages of this combined weight determination method are (1) that the expert survey ensures a broad spectrum of opinions and allows for input from different built environment disciplines, and (2) that the expert panel has tool-specific insight, methodology awareness and state of the art knowledge.

Optimizing Indoor Environmental Quality in hot arid climates

Indoor Environmental Quality (IEQ) is a key indicator of the quality of the built environment and the health of its occupants. The purpose of this study is to investigate a range of IEQ parameters in buildings located in hot, arid climates, representing some of the recurring challenges in offices. The study aims to identify the main IEQ factors and their acceptable ranges, including light, thermal comfort, air quality and noise. An IEQ index is utilized (Wagdi et. al 2017) as a tool which assesses the predefined IEQ parameters in office buildings providing a rating scheme which aggregates the obtained readings. Data collected from offices located in Dubai and Cairo is used to assess the indoor environment against defined benchmarks. The full range of parameters was monitored in a group of office spaces and the obtained readings were used to compute the IEQ index. For this investigation, all offices were completely fit out and tests were performed after at least one month of operation. The recorded results demonstrate that with careful design and informed material selection, acceptable IEQ levels can be achieved. The results and application of the index aim to provide an assessment tool to optimize design and construction practices, ultimately improving employee productivity, comfort and health.

Optimizing Indoor Environmental Quality in hot arid climates

Indoor Environmental Quality (IEQ) is a key indicator of the quality of the built environment and the health of its occupants. The purpose of this study is to investigate a range of IEQ parameters in buildings located in hot, arid climates, representing some of the recurring challenges in offices. The study aims to identify the main IEQ factors and their acceptable ranges, including light, thermal comfort, air quality and noise. An IEQ index is utilized (Wagdi et. al 2017) as a tool which assesses the predefined IEQ parameters in office buildings providing a rating scheme which aggregates the obtained readings. Data collected from offices located in Dubai and Cairo is used to assess the indoor environment against defined benchmarks. The full range of parameters was monitored in a group of office spaces and the obtained readings were used to compute the IEQ index. For this investigation, all offices were completely fit out and tests were performed after at least one month of operation. The recorded results demonstrate that with careful design and informed material selection, acceptable IEQ levels can be achieved. The results and application of the index aim to provide an assessment tool to optimize design and construction practices, ultimately improving employee productivity, comfort and health.

The Approach of Including TVOCs Concentration in the Indoor Environmental Quality Model (IEQ)—Case Studies of BREEAM Certified Office Buildings

The article analyzes the impact of measured concentrations of Total Volatile Organic Compounds (TVOC) emissions determined for four BREEAM certified buildings on the Indoor Air Quality Index (IAQindex) and the overall Indoor Environment Quality index (IEQindex). The IEQindex indicates the percentage of building users who are satisfied from the indoor environment. In existing IEQ models, currently the concentration of CO2 is mostly used to evaluate the IAQindex sub-component. Authors point out that it is recommended to use TVOC instead CO2 at pre-occupant stage where building is mainly polluted by emission from finishing products. The research provides the approach where the component related to the emission of TVOCs is implemented to IEQ model. The first stage of assessment was a test of the volatile organic compounds concentrations in case study buildings. Secondly, the analysis results were assigned into the number of dissatisfied users (PD(IAQ)) from the theoretical function given by Jokl-Fanger resulting from the Weber-Fechner equation. Finally, the overall IEQindex was calculated. The IEQ approach proposed in this paper is mainly based on a consideration of EN 15251 and scientifically accepted models.

Indoor environment quality assessment in classrooms: An integrated approach

Indoor Environmental Quality is an important issue in educational buildings since it is directly related to students’ well-being and learning activities. Indoor Environmental Quality parameters have been assessed in three representative campus building typologies (old, new, and retrofitted), in Tehran, Iran, by measurements and questionnaire (n = 842) from July 2016 to April 2017. Results have been compared to the students’ overall satisfaction level and recommended standards. According to results, minimum attention to local standards with regard to Indoor Air Quality, acoustic, and lighting, especially in the old and retrofitted buildings, seems the main reason of low environmental quality in the studied cases. Fitting a multiple regression model to the questionnaire data, a mathematical model is developed to predict the overall comfort (Indoor Environmental Quality index). Studied buildings have been ranked based on the Indoor Environmental Quality index from high quality: I (building C) to out of the comfort range: IV (building A). Moreover, results reveal that the acceptable range of each Indoor Environmental Quality parameters, especially with regard to thermal and acoustic comfort, is broader in real condition in comparison with the standards. Finally, the buildings’ annual energy consumption is used to propose a Retrofit Potential Index in order to assess the impact of comfort parameters on energy consumption by integrated analyses.

Indoor environmental quality assessment, part 2: Model reliability analysis

Indoor environmental quality index involves a set of indoor environmental quality sub-components, provides an assessment of building user comfort and satisfaction and may be used as a tool to support the design of energy-efficient buildings. Unfortunately, the unknown reliability of the indoor environmental quality model is a recognized barrier for its wider practical use. In this article, a preliminary reliability test for the indoor environmental quality model is presented, providing a correct evaluation of the measurement data results and a step-by-step guide to the expression of its uncertainty. The uncertainty based on the physical parameters is first analyzed and then corrected by considering the impacts of the instability of the physical parameters. In the end, all sources of uncertainty are recognized, including uncertainties introduced by the probability distribution of panel sensory tests. A procedure for detecting internal incongruity in the indoor environmental quality model structure is also provided, and a criterion for elimination of this syndrome is proposed. Finally, in standardized indoor environment, the estimated uncertainty of the IEQindex is presented to be no less than ±17%.

Design and Development of a Low-Cost, Portable Monitoring Device for Indoor Environment Quality

This article describes the design and development of a low-cost, portable monitoring system for indoor environment quality (IEQ). IEQ is a holistic concept that encompasses elements of indoor air quality (IAQ), indoor lighting quality (ILQ), acoustic comfort, and thermal comfort (temperature and relative humidity). The unit is intended for the monitoring of temperature, humidity, PM2.5, PM10, total VOCs (×3), CO2, CO, illuminance, and sound levels. Experiments were conducted in various environments, including a typical indoor working environment and outdoor pollution, to evaluate the unit’s potential to monitor IEQ parameters. The developed system was successfully able to monitor parameter variations, based on specific events. A custom IEQ index was devised to rate the parameter readings with a simple scoring system to calculate an overall IEQ percentage. The advantages of the proposed system, with respect to commercial units, is associated with better customisation and flexibility to implement a variety of low-cost sensors. Moreover, low-cost sensor modules reduce the overall cost to provide a comprehensive, portable, and real-time monitoring solution. This development facilities researchers and interested enthusiasts to become engaged and proactive in participating in the study, management, and improvement of IEQ.

Indoor environmental quality index for conservation environments: The importance of including particulate matter

It is commonly known that the conservation state of works of arts exhibited inside museums is strongly influenced by the indoor environmental quality (IEQ). Heritage institutions traditionally record and evaluate their IEQ by monitoring temperature, relative humidity, and -more rarely-light. However, smart use of technology enables monitoring other parameters that give a more complete insight in environmental ‘air aggressiveness’. One of this parameters is particulate matter (PM) and especially its concentration, size distribution and chemical composition. In this work, we present a selection of data sets which were obtained in a measuring campaign performed in the War Heritage Institute in Brussels, Belgium. A continuous monitoring of PM concentration with a light scattering based particle counter was performed. In addition the daily mass concentration and size distribution of airborne PM was monitored by means of Harvard impactors. The chemical composition of sampled PM was inferred from the results of XRF and IC analysis. The insights from these datasets are combined with the results of traditional environmental monitoring (temperature, relative humidity and light intensity), and assessed against the recommended guidelines for conservation environments. By using an integrated approach based on the calculation of an IEQ-index, we present a straightforward methodology to evaluate and visualize the IEQ including also continuous PM monitoring. It is clear from the results of this study how including PM in IEQ analysis allows to identify potential risks for museum collections that remain invisible when only traditional parameters are considered.

Indoor environmental quality assessment: Part 1: Choice of the indoor environmental quality sub-component models

Indoor environment quality is a relative measure of comfort perception by people exposed to the indoor conditions. It is expected that any assessment of energy performance should also include indoor comfort. This study is to review indoor environmental quality models (with respect to thermal and acoustic comfort, indoor air and lighting quality). A simplified indoor environmental quality model is also developed with consideration of EN 15251 draft ‘Guideline for using indoor environmental input parameters for the design and assessment of energy performance of buildings’. This article analyses what components should be modelled and in particular discusses the effect of different weighting schemes on the overall indoor environmental quality index. The analysis includes thermal comfort models, indoor air quality, acoustic comfort and daylight illumination versus lightning. The proposed indoor environmental quality component sub-models will give the most reliable results when the model indoor environment input data are correctly measured and disturbing influences of indoor environmental quality monitoring process are well defined and properly assessed. The final indoor environmental quality result is based on subjoining the uncertainty values achieved in panel analysis of percentage of persons dissatisfied with indoor environmental quality with corrected measurement uncertainty. All simulations for IEQindex sub-components and preliminary metrological analysis of the whole indoor environmental quality model were performed with the NIST program for Monte Carlo tests. The presented indoor environmental quality model proposal is developed to support engineers’ practice as the convenient tool for a practical assessment of building’s occupational satisfaction.

Grey preference analysis of indoor environmental factors using sub-indexes based on Weber/Fechner's law and predicted mean vote

The purpose of this study was to determine the influences of environmental parameters on common health symptoms in office buildings. A grey preference analysis based on a new indoor environment quality (IEQ) index and a controlled field survey of 91 office occupants were conducted in an office building in Guangzhou, China. The new IEQ index based on Weber/Fechner’s law and predicted mean vote (PMV) was developed and validated by our survey. In the survey, the six environmental parameters (air temperature, illumination intensity, noise level, carbon dioxide, formaldehyde and PM10) were measured. The subjects’ satisfaction levels and the nine health symptoms (eye dryness, lethargy, dry throat, headache, nausea, skin dryness, blocked nose, influenza-like symptom and chest tightness) were determined using questionnaires. The results show that the proposed IEQ index can preferentially predict the subjective sensations of occupants. PM10 was identified as the most significant environmental parameter, followed by formaldehyde, air temperature, carbon dioxide, noise level and illumination intensity. Eye dryness and lethargy were the most significant symptoms, followed by dry throat, headache, nausea, skin dryness and chest tightness. Blocked nose and influenza-like symptom were hardly reported by subjects. The findings of this study could provide a practical guidance for IEQ management to reduce unhealthy diseases for occupants.

Determining the Indoor Environment Quality for an Educational Building

Indoor environment quality, IEQ, is considered as an indicator of the level of comfort which is not confined to the thermal conditions, it includes elements such as thermal comfort, acoustic comfort, indoor air quality and visual comfort. Knowledge of IEQ is useful for rehabilitation of buildings, for example, it can indicate areas which require improvement measures of the parameters which affects indoor environment. We must consider that indicators of comfort are only valid for the stationary regime. An energy evaluation of building is required for a good interpretation of indoor environment quality index (IIEQ) depending on energy consumption and possibly to finding increase in energy consumption in order to include IIEQ in a higher class.

Energy efficiency versus indoor environmental quality in different Romanian countryside schools

The current research study, aims to couple the indoor environmental quality (IEQ) in countryside schools with energy efficiency. A detailed investigation took place on three different types of rural schools (old, new, and renovated) conveniently located for comparison purposes within a radius of 2.5km from each other. The IEQ assessment covered the period autumn 2013–spring 2014 and included both long term measurements and spot recordings. In terms of indoor air quality all three buildings performed poorly, registering average CO2 concentrations in excess of 2000–3000ppm and even approaching the health hazard level of 5000ppm. Based on these concentrations, the corresponding ventilation rates have been calculated at 2.4L/s/person (renovated school), 2.25L/s/person (new school) and 0.7L/s/person (old school). The IEQ index was calculated using the experimental data allowing the three analyzed schools to be better rated. The new and renovated buildings rank class C on the IEQ index scale and class A from an energy consumption standpoint, whereas the old building is rated D class (IEQ) and C class (energy efficiency). This shows that high energy consumption, as is the case for the old school, does not necessarily result in better comfort conditions despite their inverse correlation.

IEQ assessment on schools in the design stage

Nowadays, the indoor environment quality (IEQ) is growing as a new and very useful index of the building quality. The current literature presents the IEQ assessment based on questionnaires applied for existing building. The original approach of this study consists in the development of an IEQ index model that can be used by architects and engineers during design stage, in order to use it as an evaluation indicator or optimize the building energy consumption versus indoor environmental conditions. Based on a large database of values resulted from simulations, multiple non-linear regression models were obtained in order to predict variables such as operative temperature, indoor sound pressure level, indoor average illuminance and specific energy consumption. A predictive model for IEQ index is proposed as a function of the four quality indexes (air quality, thermal, acoustic and visual comfort). The entire approach was tested by means of a study case where the impact of windows’ size and type on the IEQ assessment is discussed for a random climate. Also, there are presented detailed results concerning the monthly variation of IEQ and its correlation with the energy consumption. The proposed method proves to be a fast and useful method to verify architectural and engineering solutions according to the IEQ estimator.

Indoor Environmental Quality Benchmarks for Air-conditioned Offices in the Subtropics

Indoor environmental quality (IEQ) of air-conditioned offices could be benchmarked by the occupants' acceptability. This study proposes a five-star IEQ benchmarking system based on an expression of the occupants' overall IEQ acceptance on thermal comfort, indoor air quality and aural and visual comfort. By using an earlier proposed IEQ index, the occupants' adaptive response of clothing adjustment for the perceived thermal environment was reported in order to determine the overall IEQ acceptance. The benchmarking parameter of a star rating system and the IEQ index were applied to express relative IEQ performance of air-conditioned offices in Hong Kong. The IEQ performance of some recommended environmentally sustainable policies for ``Excellent'' and ``Good'' offices was evaluated and compared with the existing offices. The probable IEQ in some Hong Kong offices were determined by Monte Carlo simulations from reports of surveyed studies. Among the existing office stock, results have shown that in offices which are renovated to the ``Excellent'' and ``Good'' IEQ criteria recommended by some policies, the IEQ acceptances for 5-star IEQ benchmarked offices are namely 0.95, 0.94, and 0.92, while for 3-star IEQ benchmarked offices, they are 0.89, 0.89, and 0.67 accordingly. The proposed star rating system would serve as a quantitative measure of IEQ for air-conditioned office environment in Hong Kong and given selected model parameters, it would be a useful reference for similar environments where the evaluation of an occupant is expected.

An energy performance assessment for indoor environmental quality (IEQ) acceptance in air-conditioned offices

Maintaining an acceptable indoor environmental quality (IEQ) for air-conditioned office buildings consumes a considerable amount of thermal energy. This study correlates thermal energy consumption with the overall occupant acceptance of IEQ in some air-conditioned offices. An empirical expression of an IEQ index associated with thermal comfort, indoor air quality, aural and visual comfort is used to benchmark the offices. Employing input parameters obtained from the building stocks of Hong Kong, the office portfolios regarding the thermal energy consumption and the IEQ index are determined by Monte Carlo simulations. In particular, an energy-to-acceptance ratio and an energy-to-IEQ improvement ratio are proposed to measure the performance of energy consumption for the IEQ in the air-conditioned offices. The ratios give the thermal energy consumption corresponding to a desirable percentage of IEQ acceptances and to an IEQ upgrade, respectively. The results showed a non-linear increasing trend of annual thermal energy consumption for IEQ improvement at the offices of higher IEQ benchmarks. The thermal energy consumption for visual comfort and indoor air quality would also be significant in these offices. This study provides useful information that incorporates the IEQ in air-conditioned offices into the development of performance evaluation measures for thermal energy consumption.