Applied Science, Faculty of
Non UBC
Engineering, School of (Okanagan)
DSpace
Energies 18 (7): 1740 (2025)
Perera, Ishanka
Hewage, Kasun
Rana, Anber
Sadiq, Rehan
The indoor environmental quality (IEQ) in buildings is vital for health, work efficiency, productivity, and the overall sustainability of buildings. IEQ is governed by four parameters: indoor air quality and thermal, acoustic, and visual comfort. The recent pandemic has compelled people to think beyond energy efficiency and refocus on the health, well-being, and productivity of building occupants. Despite numerous IEQ guidelines and standards, there remains a paucity of systematic research that critically examines the relationship between IEQ and building energy efficiency. This systematic review explores the existing equilibrium and identifies gaps between IEQ standards and building energy codes. Firstly, this review examined the status of the IEQ standards and identified that most of the North American IEQ guidelines cannot achieve energy efficiency targets. Secondly, existing building energy codes were reviewed to determine how well these codes fare with IEQ requirements. It was revealed that the expensive energy certification documents are more focused on IEQ than traditional energy codes. The identified factors indicate that most building energy codes can meet only indoor air quality thresholds (a subset of IEQ), while other parameters are inadequately addressed. This review revealed 19 relationships between IEQs and energy efficiency. Building energy code/IEQ guidelines developers could consider the identified 19 relationships to develop a combined set of guidelines/standards for future building stock. An integration model between IEQ and energy efficiency is proposed as a future research direction to contribute to the better design and construction of modern buildings. The findings will facilitate the construction of healthy and sustainable buildings, and they aim to generate new residential communities that achieve an optimal health–energy–carbon nexus.
Academic Editors: Piero Bevilacqua,Cynthia Cruickshank and MiroslavCˇekonReceived: 6 February 2025Revised: 23 March 2025Accepted: 25 March 2025Published: 31 March 2025Citation: Perera, I.; Hewage, K.;Rana, A.; Sadiq, R. Combining EnergyPerformance and IndoorEnvironmental Quality (IEQ) inBuildings: A Systematic Review onCommon IEQ Guidelines and EnergyCodes in North America. Energies2025, 18, 1740. https://doi.org/10.3390/en18071740Copyright: © 2025 by the authors.Licensee MDPI, Basel, Switzerland.This article is an open access articledistributed under the terms andconditions of the Creative CommonsAttribution (CC BY) license(https://creativecommons.org/licenses/by/4.0/).Systematic ReviewCombining Energy Performance and Indoor EnvironmentalQuality (IEQ) in Buildings: A Systematic Review on CommonIEQ Guidelines and Energy Codes in North AmericaIshanka Perera 1 , Kasun Hewage 1,*, Anber Rana 2 and Rehan Sadiq 11 School of Engineering, The University of British Columbia, Okanagan Campus, 3333 University Way,Kelowna, BC V1V 1V7, Canada; ishankas@student.ubc.ca (I.P.); rehan.sadiq@ubc.ca (R.S.)2 College of Built Environments, University of Washington, Seattle, WA 98195, USA; anber.rana@alumni.ubc.ca* Correspondence: kasun.hewage@ubc.caAbstract: The indoor environmental quality (IEQ) in buildings is vital for health, workefficiency, productivity, and the overall sustainability of buildings. IEQ is governed byfour parameters: indoor air quality and thermal, acoustic, and visual comfort. The recentpandemic has compelled people to think beyond energy efficiency and refocus on the health,well-being, and productivity of building occupants. Despite numerous IEQ guidelinesand standards, there remains a paucity of systematic research that critically examines therelationship between IEQ and building energy efficiency. This systematic review exploresthe existing equilibrium and identifies gaps between IEQ standards and building energycodes. Firstly, this review examined the status of the IEQ standards and identified thatmost of the North American IEQ guidelines cannot achieve energy efficiency targets.Secondly, existing building energy codes were reviewed to determine how well thesecodes fare with IEQ requirements. It was revealed that the expensive energy certificationdocuments are more focused on IEQ than traditional energy codes. The identified factorsindicate that most building energy codes can meet only indoor air quality thresholds (asubset of IEQ), while other parameters are inadequately addressed. This review revealed19 relationships between IEQs and energy efficiency. Building energy code/IEQ guidelinesdevelopers could consider the identified 19 relationships to develop a combined set ofguidelines/standards for future building stock. An integration model between IEQ andenergy efficiency is proposed as a future research direction to contribute to the better designand construction of modern buildings. The findings will facilitate the construction ofhealthy and sustainable buildings, and they aim to generate new residential communitiesthat achieve an optimal health–energy–carbon nexus.Keywords: indoor environmental quality (IEQ); thermal comfort; indoor air quality (IAQ);acoustic comfort; visual comfort; building energy efficiency; green building standards1. IntroductionThe rapid growth of the human population and increasing levels of activities haveresulted in an exponential increase in energy and resource use. Several adverse impactshave been induced due to increased energy consumption. Climate change, potential energycrises, energy poverty, geopolitical issues, and negative impacts on human health andwell-being are among the adverse effects [1]. The global building sector is one of theprimary consumers of global fossil-fuel-based energy. Buildings generate vast amountsof anthropogenic greenhouse gas (GHG) emissions [2]. Reducing building-related energyEnergies 2025, 18, 1740 https://doi.org/10.3390/en18071740Energies 2025, 18, 1740 2 of 30consumption and emissions has been a dominant aim in the building construction industryover the past decade [3,4]. Building energy use in North America is predicted to be asignificant contributor to fossil-fuel-based carbon emissions by 2025 [5,6]. In Canada, 80%of the GHG emissions are attributed to fossil-fuel-based energy usage, and out of that,the building sector is responsible for 12% of the GHG emissions [7]. There are numerousinitiatives to reduce building energy consumption and mitigate building-related emissions.The most widely applied initiatives include building energy codes and green buildingperformance standards. The primary purpose of these initiatives is to act as a policymechanism to improve energy use while reducing building-related emissions. The currentbuilding designs and construction process heavily depend on these methods since buildingenergy efficiency is mandated by regulations and laws in many countries [8]. However,the potential of these initiatives to maintain and improve the occupant-related dimensionsof building performance, including occupant health, satisfaction, and productivity, is notfully explored [9].The design and development of healthy, energy-efficient, and occupant-centric build-ings have recently become popular, as indoor living conditions remain unsatisfactory inmany buildings [10]. Domestic houses, schools, and office buildings (residential, institu-tional, and commercial) have garnered major attention here. These are the places wheremost daily human activities take place. Moreover, the aging population further contributesto increased indoor dwelling time, as they spend around 95% of their time indoors. TheCOVID-19 pandemic has contributed to significant lifestyle changes and has increasedindoor dwelling time among all age groups. Currently, several building standard orga-nizations, such as the American Society of Heating, Refrigerating, and Air-ConditioningEngineers (ASHRAE), are introducing response resources to decrease the impact and spreadof airborne infections like COVID-19 by improving indoor environmental conditions. How-ever, these response resources are still in the early development stages and do not coveroverall human health conditions, including full indoor environmental aspects with energyefficiency as a whole package. Hence, the necessity to develop comprehensive guidelinesand standards that maintain building energy efficiency and improve indoor environmentalconditions is increasing [11].The indoor conditions of buildings are determined by indoor environmental quality(IEQ) standards and relevant IEQ parameters. IEQ standards are crucial as the publicinterest is now shifting towards building indoor conditions and healthy living environ-ments. IEQ standards set the mechanisms for developing indoor environment conditionsbased on prescriptive or performance levels. Thermal comfort, indoor air quality, acousticcomfort, and visual comfort are the pillars of IEQ. The overall building design, construc-tion method, operation, and maintenance techniques directly impact a building’s indoorenvironmental conditions [12,13].The implementation of building energy codes may favor positive or negative impactson IEQ parameters based on the fundamental design differences. Most building energycodes emphasize reduced infiltration, lower air changes, and higher thermal-mass-basedinsulation [14]. Previous studies on using high thermal masses in residential buildingshave shown that hot summers adversely increase indoor temperatures [15]. Such issuesarise from the excessive use of building code details without properly accounting for thecombined effect of IEQ and energy efficiency. The recent climate events involving extremelyhot temperatures further increase the requirement for proper indoor environmental thermalbalance with energy efficiency. The 2023 summer heat wave in North America [16] and the2021 summer heat dome in the province of British Columbia, Canada [17], are the mostrecent of such events.Energies 2025, 18, 1740 3 of 30The adverse impacts of poor IEQ are not just tied to the thermal environment but alsoto the health, well-being, and workplace satisfaction of the occupants through indoor airquality [18]. Reduced infiltration and low fresh air rates can cause poor indoor air quality.Likewise, improved indoor air quality in occupant spaces can enhance work productivityby 0.5–5%. The equivalent monetary value of this productivity increase is estimated at USD12–125 billion annually [19]. Furthermore, the global annual extra expenses are aroundUSD 100 billion due to poor IAQ issues, including the treatment of SBS and other illnesses,worker absenteeism, and maintenance costs for problematic buildings [19]. Sick buildingsyndrome (SBS) is one of the most common adverse effects residents suffer in energy-efficient buildings related to indoor air [20]. With SBS, occupants may experience adversehealth symptoms without a specific illness when indoor climate control methods are ineffect under energy code practices. Hence, indoor air quality is also essential for the healthof occupants and the overall sustainability of the building through energy, emissions, andeconomic performance. In North America, adverse impacts on building IAQ due to energyefficiency practices are well documented. The National Institute of Occupational Safety andHealth in the United States of America has identified inadequate ventilation rates as theprimary contributor to SBS [21,22]. In Canada, PM2.5, a major indoor pollutant, is estimatedto cause CAD 5.5 billion worth of healthcare costs associated with premature deaths [23].Likewise, problems of poor visual and acoustic comfort are documented even inenergy-efficient office buildings. For instance, a statistical survey of 120 employees whoshifted from an old conventional office building to a low-energy building revealed that de-spite improved thermal comfort, indoor air quality and levels of visual and acoustic comfortdecreased. Similarly, a study conducted on two LEED (Leadership in Energy and Environ-ment Design)-certified buildings found that over 50% of the occupants believed that theindoor conditions were negatively influencing their work performance and health [22,24].Therefore, the above practical cases highlight major conflicts between the design of thebuilding envelope and energy systems to achieve higher energy efficiency and IEQ of occu-pant spaces. This indicates that the relationship between IEQ and existing building energycodes is poorly understood. Based on the existing body of knowledge, very few studieshave attempted to identify these dynamics between IEQ standards and building energycodes in a combined platform. Indoor conditions and occupants’ health are extremely sen-sitive to design methods and energy-saving practices in occupant-centric building designs.Therefore, the evaluation of all the IEQ parameters needs to be comprehensively exploredin relation to building energy efficiency. In particular, the significance of proper IEQ levelsand quality of living spaces have been highlighted since the COVID-19 pandemic.The primary objective of this study is to identify the current state of commonlyavailable IEQ standards and the interrelationships between IEQ standards and buildingenergy codes/standards from a North American perspective. This review focuses on thecommon IEQ parameters, current guidelines, standards for IEQ maintenance, variousassessment models to analyze IEQs, and interrelationships between IEQs and existingbuilding energy codes. Moreover, the limitations and missing aspects of these NorthAmerican codes are discussed compared to other global standards as to how they shouldbe revised or modified accordingly. Building energy code developers, building-relatedmandates, and policymakers could greatly benefit from the content of this review. Moreover,future research directions could be derived based on the findings to integrate the IEQstandard assessments into building energy efficiency enhancement methods.2. Materials and MethodsThis review investigates the existing status of the common North-America-basedIEQ standards and guidelines and their interaction with building energy codes and greenEnergies 2025, 18, 1740 4 of 30building standards. This work aims to see how well IEQ standards align with existingenergy codes and standards and to identify conflicts, synergies, and overall implicationsfor sustainable building policies and practices. To achieve these objectives, the PreferredReporting Items for Systemic Reviews and Meta-Analysis (PRISMA) 2020 guidelines werefollowed, and a systematic content analysis was conducted [25]. The PRISMA guidelineswere first introduced in 2009 as a technique to perform systematic analysis. The PRISMA2020 guidelines are the latest revision that considers advancements in data identification,collection, and analysis. Content analysis is a widely used research tool to determine thepresence and relationships of certain concepts and words where qualitative data can bepresented under certain themes. The integration of the PRISMA guidelines and content inthis work ensures that the relevant literature is identified and themes and trends in existingIEQ standards and building energy codes are uncovered.The following figure, Figure 1, describes the results of the search and selection process, fromthe number of records identified in the search to the number of studies included in this review,using the PRISMA 2020 flow diagram for systematic reviews. The flow diagram was madewith the assistance of the Shinyapp tool available on the Prisma 2020 statement website [26].A detailed PRISMA 2020 checklist is provided in the Supplementary Materials File S1 thatexplains further details on the process of data extraction from databases.Energies 2025, 18, x FOR PEER REVIEW 4 of 31 2. Materials and Methods This review investigates the existing status of the common North-America-based IEQ standards and guidelines and their interaction with building energy codes and green building standards. This work aims to see how well IEQ standards align with existing energy codes and tandards and to identify c nflicts, synergies, n overall implications for sustainable building policies and practices. To achiev th e objectives, the Preferred Reporting Items for Systemic Reviews and Meta-Analysis (PRISMA) 2020 guid lin s were followed, and a systematic ontent an lysis w s conducted [25]. The PRISMA guidelines were first i troduced in 2009 as a technique to perform systematic analysis. The PRISMA 2020 guidelines are the latest revision that considers advance ents in data identification, collection, a d analysis. Content analysis is a widely used research tool to determine the presence and relationships of certain concepts and words where qualitative data can be rese ted under certain themes. The integration of the PRISMA guidelines an conte t in this work e sures that the relevant literature is identified and themes a d trends in exist-ing IEQ standards and building energy codes are uncovered. The following figure, Figure 1, describes the results of the search and selection pro-cess, from the number of records identified in the search to the number of studies included in this review, using the PRISMA 2020 flow diagram for systematic reviews. The flo diagram was made with the assistance of the Shinyapp tool available on the Prisma 2020 statement website [26]. A detailed PRISMA 2020 checklist is provided in the Supplemen-tary Materials File S1 that explains further details on the process of data extraction from databases. Figure 1. The PRISMA 2020 flow diagram for the results of the search and selection process. Figure 1. The PRISMA 2020 flow diagram for the results of the search and selection process.Data collection is the first step in the PRISMA 2020 method. The data collectionprocess involved keyword searches in peer-reviewed journals and scientific databasessuch as Compendex Engineering Village, Google Scholar, and IEEE Xplore [27,28]. TheseEnergies 2025, 18, 1740 5 of 30three databases were selected based on their broad coverage of engineering disciplines,ease of access, and global reach. In particular, Compendex Engineering Village and IEEEXplore contain a vast collection of peer-reviewed journals and book chapters. Moreover,the inbuilt automation features such as sorting, abstract summarization, and key wordcombinations are available in the Compendex Engineering Village database with fullaccess to Elsevier data. Moreover, the Compendex Engineering Village database narrowsdown the Elsevier database through the lens of engineering disciplines. Since this reviewdoes not include any statistical data and experiments, statistical databases were excludedfrom the research data extraction process. The content gathered by the selected databasesincluded peer-reviewed research articles, conference publications, and scientific reports.Moreover, government-issued documents, provincial or regional municipality reports,North American standards and guidelines (e.g., ASHRAE, WHO, and ISO), and relevantwebsites from several organizations were also identified.Data related to specific guidelines/standards were mostly adopted from direct onlinesources through online access to the standards (depending on the availability of the accesswithin the research/study institute). This was carried out due to the continuously updatingnature of the guidelines and standards.Screening is the second main step after the report/data search. Some of the primarykeywords used for data screening were ‘thermal comfort’, ‘indoor environmental quality’,‘air quality’, ‘standards and policies for IEQ and energy efficiency’, ‘North Americanbuilding energy codes’, ‘building energy code and standards’, ‘energy efficiency and humancomfort’, ‘building energy codes’, ‘energy certification standards’, and ‘green buildings’.The keywords were used to filter the number of previous studies while searching in theabove three databases. This review primarily focused on indoor environmental qualityand building energy efficiency. IEQ is fundamentally developed based on thermal comfort,air quality, acoustic comfort, and visual comfort. Therefore, it is a must to include themost important keywords for the indoor environmental quality in the database search.On the energy efficiency aspects, the key words of ‘energy efficiency’, ‘green building’,and ‘energy performance enhance’ were used to narrow the search records where IEQand energy performance were both considered. Moreover, this review focused on theinterrelations and connections between these two aspects. Hence, combined keywordsbetween IEQ and energy efficiency were used in the databases to narrow down specificstudies and records that considered both of these aspects. The combined keyword search isa specific feature used in the Compendex Engineering Village database from Elsevier. NoAI-based instruments were used to screen and summarize the existing literature prior to theinvestigation. The inbuilt automation tools, such as sorting and duplicate removal, wereused inside some of the databases to screen the vast amounts of records in the keywordsearch resultsWhile specifying the inclusion and exclusion criteria for the above source selections,any data and sources after the COVID-19 pandemic were given priority. Moreover, sincethis review is primarily about energy codes and IEQ guides, any relevant revisions andguidelines before 2019 were also considered when the reference was limited. The scope ofthe content analysis was limited to the codes and guidelines in the North American region.These inclusion criteria were essential, as numerous IEQ guidelines and energy codes areavailable globally, making a thorough analysis technically and practically non-feasible.In addition, narrowing the geographical location can help to focus and discuss tailoringpolices and standards specific to the region.After the keyword search, most relevant articles were selected for a thorough readingbased on the abstract details of the studies. However, since this review mainly focuseson existing energy codes and IEQ guidelines, a review of the reports, papers, and relayedEnergies 2025, 18, 1740 6 of 30guidelines was conducted to support the findings. Peer-reviewed publications focusingon building energy efficiency, IEQ, or building sustainability from a North Americanperspective were prioritized. All the data sources and references are cited throughout thereview and can be found as a separate bibliography list at the end of the manuscript andSupplementary Materials.A content analysis was performed on the final list of studies, reports, guidelines, andstandards. In the context of the research objectives, a graphical overview of basic stepsfor data analysis is provided in Figure 2. Please note that under the data source graphics,the figure only presents a limited number of sources for the purpose of illustration. Thefirst step involved the development of a conceptual framework based on how differentIEQ parameters were defined in the literature. In the second step, the IEQ standards andguidelines were reviewed to identify the scope, limitations, and assumptions. In the thirdstage, building energy codes and standards were compared with the IEQ standards toassess how well these two codes and standards aligned with each other. In the last step,particular emphasis was given regarding the future directions for building energy policiesand standards in light of the current standards. Recommendations were formulated fordesigners, engineers, and policymakers to facilitate the development of a more sustainablebuilding sector.Energies 2025, 18, x FOR PEER REVIEW 6 of 31 After the keyword search, most relevant articles were selected for a thorough reading based on the abstract details of the studies. However, since this review mainly focuses on existing energy codes and IEQ guidelines, a review of the reports, papers, and relayed li building energy efficiency, IEQ, or build ng sustain bility from a North American per-spective were prio tized. All the dat sources and references are cited thr t . l t i , , , . In the context of the res arch objectives, a graphical overview of basic teps for data nalysis i provided in Figure 2. Please note that under the data source graphics, the figure only present a limited number of sources for the purpose of illustration. The first step involved the development of a conceptual framework based on h w different IEQ parameters were d fined i the literature. In the second step, the IEQ standards and guide-lines were review d to identify the scop , limitations, and assumptions. In the third stage, building energy codes an standards were compared with the IEQ standards to assess how well thes two codes and standards aligned with each other. In the last st p, partic-ular emphasis was given regarding the future directions f r building energy policies and standards in light of the current stand rds. Recommendations were formulated for de-signers, engineers, and policymakers to facilitate the development of a ore s stai a le il i sect r. Figure 2. Content analysis [29–31].Energies 2025, 18, 1740 7 of 303. IEQ: Parameters and Indicators for the Codes and GuidelinesThe four main IEQ parameters are indoor air quality and thermal, acoustic, and vi-sual comfort [32]. Apart from these main four, several other parameters are defined inthe literature as a subcategory of these four parameters (e.g., indoor air velocity, relativehumidity, PM levels, etc.) [32,33]. These primary IEQ parameters are common for anybuilding archetype. However, their relative importance can vary, with the highest impor-tance associated with residential buildings. In order to identify their connection to energyefficiency, it is important to establish the basic definitions and concepts related to thesefundamental IEQ parameters. The third section of this review is dedicated to identifyingthe primary IEQ parameters and their basics. A clear definition of these IEQ parametersis required, as this review investigates the IEQ guidelines and energy codes on the basisof these parameters. Hence, the fundamental parameters and their relevant indicators areidentified here.3.1. Thermal Comfort (TC)Thermal comfort is defined as a “Condition of mind which expresses satisfaction withthermal conditions” according to the ISO 7730 [34] and ASHRAE 55 standards [29,35,36].Defining an exact thermal comfort level is difficult, since personal thermal sensation playsa major role. According to ASHRAE, a building can be labelled as thermally comfortable if80% of the occupants are satisfied with the thermal conditions [35]. Thermal comfort canbe defined by the following:• Air temperature and velocity;• Operative temperature (a combination of indoor air temperature and mean radi-ant temperature);• Relative humidity;• Occupant clothing values (Clo value);• Human metabolic rate (based on activity).Several methods are defied in the literature to evaluate the thermal comfort of a build-ing. The Fanger analysis method is one of the most commonly used methods. The Fangermethod uses thermal sensation and thermal dissatisfaction experienced by occupants toassess thermal comfort limits and balance. The predicted mean vote (PMV) and predictedpercentage of dissatisfaction (PPD) are used here. The PMV index aims to predict themean value of votes from a set of occupants using a seven-point thermal sensation scale(+5: extreme hot, 0: neutral, and −5: extreme cold). The PMV index can be calculated withthe mathematical calculation procedures given in ISO 7730 or through building modellingsoftware such as Design Builder (v7.3.0.043) and SIMSCALE (v2021-July) [37]. Several userinputs are needed when using simulation-software-based PMV calculation models. Simu-lated temperature (as the mean radiant temperature), air velocity, and clothing insulationare provided by the software after the energy simulations and as user inputs to calculatethe PMV index. However, the accuracy of thermal comfort PMV data from the softwarecan be different from real-life conditions. Only a generic idea about the thermal comfort ofa potential new building design can be obtained from these software calculations. Real-life surveys and data collection should be carried out to validate software-based thermalcomfort data. Overall, the final PMV value for a space only delivers the thermal sensationof the general population rather than individual thermal satisfaction. However, the PPDindex can be used further to express the level of satisfaction through the percentage ofdissatisfaction. The acceptable PMV range is from −0.5 to +0.5 with a PPD value of lessthan 10%, according to ASHRAE 55 [38,39]. Other popular methods to evaluate thermalcomfort are the ASHRAE 55 simplified static graph method and the adaptive-model-basedmethod. The simplified static graph method is based on a graphical method based onEnergies 2025, 18, 1740 8 of 30psychometric charts. The adaptive method is based on naturally ventilated buildings andelevated air velocities, where two thermal comfort acceptability ranges are defined. Theinfluence on the above-mentioned thermal comfort and its relevant parameters from theenergy efficiency measures are evaluated in the sections below.3.2. Indoor Air Quality (IAQ)The indoor air quality is defined as the “Interaction between the climate, location,construction system, building materials, furnishing, building occupants, and all otherprocesses within the building” [40]. Indoor air quality (IAQ) plays a crucial role in occupanthealth and well-being. A wide range of illnesses and human-health-related issues areassociated with poor IAQ. Both short-term and long-term exposure to improper IAQcan lead to adverse health effects, including headaches, allergies, skin irritation, asthma,dizziness, cancer, and death [19]. According to the United States Environmental ProtectionAgency (EPA), poor IAQ is one of the top five environmental health risks to the public.Furthermore, IAQ is crucial for the overall energy efficiency and energy consumption ofa building [19]. The EPA has categorized pollutants of concern into seven categories [41].Some common pollutants include the following:1. Combustion by-products (e.g., CO2, CO, particulate matter);2. Natural origin substances (e.g., radon, mould, pollen, pet dander);3. Biological agents;4. Chemical contaminants;5. Pesticides, asbestos;6. Ozone;7. Volatile organic compounds.Evaluating indoor air quality is complex and involves the consideration and evalua-tion of several factors. It depends on a wide range of environmental and building-relatedparameters, including indoor emissions levels, outside air pollution and emissions, chemi-cal reactions, building air exchange cycles, ventilation and HVAC design, building envelopeconstruction material, occupant activities, indoor and outdoor air temperatures, and rel-ative humidity. These factors can be divided into three pillars: building characteristics,indoor conditions and activities, and outdoor conditions of the ambient environment.A building’s characteristics can be changed early to improve the material selectionand HVAC designs. However, this is a field that is continuously evolving and adaptingto new building materials. Also, associated adverse health effects are continuously beingidentified and categorized over time [19]. The indoor conditions governing IAQ can bechanged and altered based on the occupants’ daily activities. The factors affecting IAQ inthis category have the flexibility to change and can be controlled the most [42]. Outsideenvironmental emissions and pollutants depend on exterior parameters and are out ofthe control of the building occupants. Indoor and outdoor pollutants can be measuredusing several indices. Most IAQ indices are based on pollutant substances and gases [19].If a particular substance or gas is beyond the allowable maximum level, then the IAQ isnot acceptable, and immediate actions need to be taken based on the risk level regardinghuman health [43–45]. Table 1 presents some of the common pollutants used to defineIAQ levels.Energies 2025, 18, 1740 9 of 30Table 1. Common indicators/substance levels to indicate IAQ levels [41].CO2 (ppm)—carbon dioxide level TVOC—Total volatile organic compound levelsCO—carbon monoxide level VOC—volatile organic compound levelsBenzene NO2—Nitrogen dioxide levelPM 10 (µg/m3)—particulate matter (10 µm or less) O3—ozonePM 2.5 (µg/m3)—particulate matter (2.5 µm or less) Radon levelRH—relative humidity SO2—sulfur dioxide levelAirspeed NH3—ammonia levelTemperature NO—nitric oxideDust and pollen, fungi Odor, bacteriaExperimental and numerical techniques are frequently used in combination to evaluateIAQ [46,47]. Continuous monitoring of IAQ is often impractical due to higher associatedcosts. However, in recent years, the development of low-cost digital gas sensors, based onnanomaterials, and better computational tools and techniques has enabled IAQ measure-ments on a larger scale [48]. Numerical techniques have the advantage of being able tobe scaled to a desired time and geometrical scale. Computational fluid dynamics (CFD)is one of the most common techniques and is based on partial differential equations [49].Experimental techniques, on the other hand, involve scaled-down and full-scale models inlaboratories or real environments.The relevance of the above-mentioned IAQ aspects and its indicators in terms of energyefficiency are evaluated in the latter sections of this paper. In particular, the identifiedIAQ sources and indicators are closely related to the building envelope materials that arecommonly used when implementing higher energy efficiency measures.3.3. Visual Comfort (VC)Visual comfort is defined as a “Subjective condition of visual well-being induced bythe visual surroundings” [50]. In other words, it is the subjective reaction of humans tothe quality and quantity of the lighting available within the space considered. Lighting,measured as the luminance level, can directly impact human health conditions (eye strain,soreness, headache) and work efficiency. Poor lighting conditions can influence attentionand concentration levels, resulting in safety hazards. The connections between lightingconditions and work efficiency in office buildings were investigated in some existingstudies [51,52]. It was revealed that both the light source and overall lighting conditionsdirectly affect office workers’ efficiency and mood, which are closely tied to indoor visualcomfort. Sub-aspects such as luminosity, glare, light quality, daylight, outside views,and glazing must also be considered to determine the overall lighting conditions [53].The International Commission on Illumination (CIE) categorizes the natural light quantity,distribution of light, and illuminance as the most critical parameters affecting visual comfort(Table 2).In general, there are two standard practices for evaluating visual comfort. One isthe ‘non-annoyance approach’, where the qualitative and quantitative measures of visualdiscomfort are discussed. Parameters of the non-annoyance approach are easier to measureand identify, such as glare, watering eyes, etc. [54]. The second approach is to consider thewell-being of occupants, where the positive effects generated by lighting on the well-beingof occupants are considered. The Visual Comfort Probability (VCP) system, introduced bythe Illuminating Engineering Society of North America (IESNA), is used to define-glarerelated discomfort and is defined on a scale of 0–100 [55].Energies 2025, 18, 1740 10 of 30Table 2. Common parameters for visual comfort [56].Parameter DescriptionsNatural light quantityNatural light quantity is associated with useful daylight illuminance (UDI) or daylight autonomy(DA). DA reflects the number of hours that a defined daylight level is above throughout the year.Also, there are other indices involving natural daylight, such as the daylight factor (DF), continuousdaylight autonomy (DAcon), and spatial daylight autonomy (sDA).Distribution of lightperceived by the eyeThe change in the light intensity of space is considered here with the time that the human eye takes toadjust to it. Under dimmed-light conditions, the eye’s perceived intensity of the light is different thanthe actual intensity (dimmed light intensity). Illuminance uniformity (UO) can be used to evaluatethe light distribution.Illuminance, assessing thequantity of lightIlluminance is the measure of how much light illuminates a surface, which is measured in lux. Also,1 lux is defined as the total luminous flux on a unit surface area (1 lumen per 1 m2). Thelighting-related standards specify the minimum illuminance levels required for daily tasks. Whendefining the task lux level, most standards consider the task area, immediate surroundings, andbackground area (e.g., the Illuminating Engineering Society of North America lighting handbook).Similar to indoor air quality, visual comfort is closely tied to the building envelopefactors in terms of its relation to energy efficiency. The latter sections of this review evaluatethe connection between the above-mentioned visual comfort aspects and building energyefficiency enhancement through the lens of building energy code/standards practices.3.4. Acoustic Comfort (AC)Acoustic comfort is defined as “a state of contentment with acoustic conditions” [57].Acoustic comfort may not always directly affect human health other than through discom-fort and exhaustion. However, long-term exposure can cause irreversible damage. Therecan be indirect impacts due to a lack of acoustic comfort, such as a reduction in workefficiency, not having proper sleep time, and sleep disturbances [58,59].The relative importance of acoustic comfort is higher in offices, classrooms, andother commercial-type buildings than in generic residential spaces. Occupants have morecontrol over sound levels in residential spaces, and acoustic comfort is a direct functionof occupant actions. Similar to other IEQ parameters, residential constructions prioritizeenergy efficiency compared to acoustic comfort levels [60].Acoustic comfort is evaluated by considering several sound-related measurements,including sound pressure (measured in decibels/dB), sound power (Watts), and soundintensity (dB.Watts/m2). Based on these measurements, various indicators have beendeveloped to assess acoustic comfort performance. These indicators can be classified intodifferent categories based on the perspective of acoustic quality and acoustic comfort.Table 3 includes some common acoustic indicator categories observed in the literature.Category 1 includes acoustic indicators reflecting the acoustic insulation performance ofbuildings. These indicators are commonly used in building construction codes. Category 2includes indicators of human perceptions against undesired noises and disturbances, whilethe overall acoustic quality within an environment is considered under the indicators incategory 3 (e.g., sound absorption and reflection indicators from inside surfaces are notedhere). These indicators are crucial for conference or meeting rooms, movie theatres, audito-riums, or classrooms. On-site measurements, laboratory experiments, and simulations arecommon for assessing acoustic comfort.Energies 2025, 18, 1740 11 of 30Table 3. Categories of acoustic comfort and quality indicators [61,62].Category 1 Category 2 Category 3Acoustic performance index (AP) Balanced noise criterion (NCB) Articulation index (AI)Weighted normalized impact soundpressure level of floor (L’nw) Combined noise index (CNI)Late arrival sound/strength of the latearriving (Glate)Weighted sound reduction index (Rw) Noise criterion curves (NC) Speech clarity (C50)The noise level produced bydiscontinuous service equipment (Lic)Room criterion (RC) Speech intelligibility index (SII)The noise level produced by continuousservice equipment (Lid)Noise rating curves (NR) Speech transmission index (STI)The above-mentioned acoustic comfort parameters and their subcategories are in-fluenced by various methods used to enhance energy efficiency. In particular, buildingenvelope materials and envelope design criteria can affect acoustic comfort levels signif-icantly. The followings sections discuss how energy efficiency codes/guidelines discussacoustic comfort and what are the specific relationships.4. IEQ Guidelines and StandardsIEQ encompasses the indoor environmental factors of IAQ and visual, acoustic, andthermal comfort. A set of government or non-governmental guidelines and standardsprovide limits for the different indoor parameters identified above to ensure the health andcomfort of occupants [57]. In broad terms, IEQ guidelines can be defined as informativedocuments that provide practices and procedures needed to achieve acceptable levels of theabove-defined IEQ parameters, ensuring the well-being and health of occupants. On theother hand, a standard is defined as a “document, established by consensus and approvedby a recognized body, that provides, for common and repeated use, rules, guidelines, orcharacteristics for activities or their results, aimed at the achievement of the optimum degreeof order in a given context” [63]. Compared to standards, guidelines are not legally binding.There are many guidelines and standards that exist to govern the IEQ of buildingsaround the world. The focus area of IEQ guidelines and standards can vary based on thegeographical location and social and economic conditions. For instance, more priority maybe given to indoor air quality and acoustic comfort in a heavily air-polluted city, whilemore focus will be given to thermal comfort in regions with extremely cold or hot climateconditions. Several organizations have developed national or regional-level guidelines andregulations based on such conditions. Table 4 lists the reviewed IEQ mandates, guidelines,and standards in the North America and the identified strengths and limitations. Thissection of the review identifies the existing status of North American IEQ guidelines andtheir connections with building energy efficiency. Figure 3 gives an overview of the focusof these standards and guidelines in terms of the IEQ parameters outlined in Section 3 andbuilding energy efficiency.Energies 2025, 18, 1740 12 of 30Table 4. Common indoor environmental quality standards and guidelines in North America.IEQ Guideline/Standardand Policy Key Focus Area/Strengths LimitationsAssessmentCriteriaConsiderEnergyEfficiency/PerformanceRef.• ANSI/ASHRAE Standard62.2-2022, Ventilation andAcceptable Indoor AirQuality inResidential Buildings• ANSI/ASHRAE Standard62.1-2022, Ventilation andAcceptable Indoor AirQuality inCommercial Buildings• ASHRAE has beenproviding variousstandards for almost alltypes of buildings relatedto IEQ.• Standards 62.1 and 62.2provide minimumrequirements to achieveacceptable IAQ viaventilation, mechanicalexhaust, and source control.• Regular updates andproper guidelines areprovided to constructors,designers, andother stakeholders.• Details could overlap dueto the vast number ofavailable standardsand guidelines.• The building designs arerestricted to severalconditions and limits.• The public or specificstakeholders may find ithard to identify orcomprehend theneeded information.• Most of these guidelinesand procedures arevoluntary-based standards.Governments could adoptthese and make theirmandates based onthe requirements.IAQEnergy efficiency isconsidered to a certainlimit throughHVAC design.[30,31,64]ASHRAE Standard 55, ThermalEnvironmental Conditions forHuman Occupancy• Provides detailedguidelines for achievingoccupant thermal comfortunder various conditions.• Easy-to-understand tablesand graphical methodsare presented.• Thermal comfortassessment surveysare provided.• A thorough understating ofTC assessment methods isneeded withcomprehensive knowledgefrom the ASHRAEhandbook fundamentals.• Each TC assessmentmethod is limited to certaincriteria and limitations.TC No [29]OSHA IAQ Guidelines,Occupational Safety and HealthAdministration guidelines on IAQ• OSHA air qualityguidelines provideventilation requirements forworkers based on ASHRAE62.1.• Discusses mold andmoisture, VOCs, and CO2levels.• Specific IAQ standardlevels for most pollutantsare not defined.IAQ No [65,66]EPA Indoor Air Quality (IAQ)Guidelines, U.S. EnvironmentalProtection Agency guidance forIAQ in buildings• Compliance with ASHRAE62.1 and 62.2.• Indoor pollution buildup ismainly tackled throughHVAC designs.• A comprehensive set ofIAQ guidelines.• Most building types areconsidered whendefining IAQ.• These are mainly guidelinesand voluntary-based adaptations.• The detailed,comprehensive nature isuseless since it is nota mandate.IAQ No [41,67]WELL Building Standard V2• Covers air, temperature,sound, and lighting foroccupant health andwell-being.• A holistic set of standardsthat actively looks intohuman health.• Adaptable for severalbuilding archetypes.• The certification cost isknown to be very high inthe Well V2 standard.• Requires significantinstrumentation, testing,and data collection.IAQTCACVCNot directly, but lightingoptimization cansave energy.[68]IES-ANSI/IES RP 1, NationalStandard Practice for OfficeLighting• Comprehensive guidelinesfor indoorlighting conditions.• Covers all types ofindoor spaces.• ANSI/IES RP 1 emphasizeslighting uniformity, glarecontrol, and daylighting.• Focus is only orientedtowards lightingenvironment andilluminance.Energy-efficiency-orientedlighting practices are notexplored much.• Minimum lighting needsare based on the averagesample population and notage-based categories.VC No [69,70]Energies 2025, 18, 1740 13 of 30Table 4. Cont.IEQ Guideline/Standardand Policy Key Focus Area/Strengths LimitationsAssessmentCriteriaConsiderEnergyEfficiency/PerformanceRef.BC Building Code, 2024 Canada(Provincial Regulations)• A general building energyconstruction code focusingon BC, Canada.• Heating, ventilating, andair-conditioningare discussed.• Recommends using thebasics of ASHRAE 62.1 forventilation and not specificIAQ assessment.IAQ—butnotspecific tohealthYes [71,72]Health Canada IAQ Guidelines,Indoor air qualityrecommendations for variouspollutants and exposure limits• Mainly focuses on indoorair pollutantthreshold limits.• Only the pollutantthreshold limitsare defined.• Not a comprehensiveguideline on IAQ.IAQ No [73,74]CSA Z317.2, Ventilation andthermal comfort: Canada• Outlines the heating,ventilation, andair-conditioning aspects.• Provides adequateguidelines for designingand maintaining IAQ andTC in healthcare buildings.• Limited only tohealthcare facilities.• Highly specific forCanadian regions, andothers may not be able toadopt itscomprehensive guidelines.TCIAQ Yes [75]NOM-015-STPS-2001, Mexico• A Mexican-based thermalcomfort standardfor workplaces.• Human health andworkplace safety arefocused on here.• A basic upper- andlower-bound temperaturelimits are provided.• Only suitable for dry,semi-arid hot climateTC No [76]CSA Z412, standards forergonomic performance: Canada• Designed foroffice ergonomics.• Multiple aspects of lighting(artificial, natural)are discussed.• Only lighting-basedergonomics are discussed. VC No [77]NOM-013-ENER-2013, Energyefficiency and lighting comfortstandards• Mexican-based standardson lighting andenergy efficiency.• Covers a wide range ofindoor spaces in manybuilding archetypes.• Heavily emphasize energysavings while maintainingproper lighting levels.• Not directly human-health-and well-being-oriented;mainly forenergy efficiency.VC Yes [78]ELI’s (Environmental LawInstitute) Database of State:Indoor Air Quality Laws• A comprehensive collectionof laws reflecting a range ofUSA’s policy strategies toenhance the indoorair quality.• The database of policies isfreely available tothe public.• Mostly it contains laws andregulations, which could betoo technical for thegeneral public.• Only focuses on indoor airquality under overallIEQ parameters.IAQ No [79]ISO 7730:2005 Ergonomics of thethermal environment• Local thermal comfortparameters/criteria areconsidered here.• Analytical determinationand interpretation ofthermal comfort using thecalculation of the PMV andPPD indices and localthermal comfort criteria.• ISO standard mentionscultural, national, andgeographical differences,unlike ASHRAE 55.• PMV and PPD methods areused to predict/calculategeneral thermal sensationsrather than adaptivetechniques. Only devotedto mechanical ventilationin buildings.• The standard does notreceive frequent updatescompared to ASHRAE 55.• Users may need to integrateother ISO standards for themissing IEQ aspects.TC Yes [34]Energies 2025, 18, 1740 14 of 30Table 4. Cont.IEQ Guideline/Standardand Policy Key Focus Area/Strengths LimitationsAssessmentCriteriaConsiderEnergyEfficiency/PerformanceRef.ISO 353 Acoustics, Measurementof sound absorption in areverberation room• The standards formeasuring the soundabsorption coefficientof materials.• Only focuses on soundabsorption levels.• Not suitable for multipletypes of indoor spaces.AC No [80]ISO 717-1:2020 Acoustics, Ratingof sound insulation in buildingsand of building elements• Airborne sound insulationvalues are defined forcommon envelope elements(walls, roofs,doors, windows).• Various noise sources areconsidered with a goodrange in terms of soundlevel spectra.• Only the building elementsound insulation level isconsidered as the index.• Not freely available to thegeneral public.AC No [81,82]REHVA: The Federation ofEuropean Heating, Ventilation,and Air ConditioningAssociations: Ventilation andindoor air quality guidelines• The primary focus isbuilding ventilation, andseveral ventilation-relatedaspects are discussed inthe guidelines.• Health-based ventilationguidelines for the EU.• Clean ventilation systemdesign and maintenanceguidelines (GB8).• Hygiene requirementguidelines for ventilationand air-conditioning (GB9).• REHVA COVID-19 updatedguidance directory.• Most of the availableguidelines focus onbuilding ventilation andindoor air quality.• Focuses on the thermalcomfort guidelines, andstandards are not present atthe time of writingthis paper.IAQ No [83]Illuminating EngineeringSociety (IES)IES RP-1-12, American NationalStandard Practice forOffice LightingIES RP-29-06, Lighting forHospitals and HealthCare FacilitiesIES LightingHandbook guidelines• These IES standards definethe lighting requirementsfor the consideredspace types.• Important design aspectsare covered, such as lightuniformity, daylighting,and glare.• Visual comfort is the onlyIEQ parameterconsidered here.• Not all the types of spacesare considered in theIES standards.VC No [70,84]International Commission onIllumination (CIE)ISO/CIE 8995, Lightingof WorkplaceCIE S 015/E 2005, Lighting ofoutdoor workplacesISO 30061:2007 CIE S 020,Emergency lighting• CIE has developed severalguidelines, best practices,and standards for buildinglighting andoutdoor lighting).• A vast scope of lightingapplications is consideredhere, with various aspects.• Only the visual comfortaspect of IEQ is considered.• Due to the vast number ofstandards and guidelinesavailable, it might not beeasy to select the requireduser guidelines.• Some guidelines andstandards are combinedwith ISO standards.VC No [85,86]Residential Indoor Air QualityGuidelines (RIAQG): Canada• Pollutant sources andidentification guidelines.• Health effects andrecommended exposurelevels in Canadian homes.• Only a guideline and basicinformation about airpollutants rather than anactual mandate.• Limited details relating tobuilding construction andoperation. However,important information ispresented for pollutantidentification and theirmaintenance toaccepted levels.IAQ No [74]ISO 16000-1, Indoor air, Generalaspects of IAQ andmeasurement strategyISO 16000-6, VOC (VolatileOrganic Compounds)measurement in indoor air• Main focus is IAQmeasurement techniques.• Uses several referenceparameters/air qualitypollutant types.• Limited practical guidancefor residents/occupants.• More oriented towardsdesign/construction aspects.• Requires regularmonitoring and significantinstrumentation.IAQ No [87,88]Energies 2025, 18, 1740 15 of 30Table 4. Cont.IEQ Guideline/Standardand Policy Key Focus Area/Strengths LimitationsAssessmentCriteriaConsiderEnergyEfficiency/PerformanceRef.World Health Organization(WHO) guidelines for indoor airquality: Selected Pollutants• WHO guidelines focus onhealth risks fromcommonly availablechemicals in indoor air.• Health risks, exposurepathways, andrecommended pollutantlevels are discussed here.• Only selected chemicals arepresented here. (e.g.,benzene, carbon monoxide,radon, etc.).• Countries may or may notconsider this guideline, asthe WHO does not mandateit for human health.IAQ No [89]Energies 2025, 18, x FOR PEER REVIEW 15 of 31 Figure 3. Percentages of guidelines under each IEQ parameter and energy efficiency assessment. This review of 23 North American guidelines and standards indicated that the ma-jority are focused on only a specific parameter and do not provide impacts regarding other IEQ dimensions. For instance, ASHRAE standard 55 is focused on thermal comfort [29]. A thermally comfortable indoor environment does not always indicate that other indoor parameters are within acceptable limits or that they are performing equally or better. For instance, a field study on a dormitory building ventilated by split air-conditioning showed a high thermal comfort (80%) rating indicated by the occupants [90]. However, when com-pared against a similar naturally ventilated building with only 60% acceptance, the air contained a 1.6 times higher concentration of CO2 or poor air quality. Likewise, a building can achieve acceptable levels of thermal comfort but have poor acoustics. For example, a survey study in the United States on occupants of office buildings with radiant heating and cooling systems indicated that majority of the participants had low satisfaction with the office acoustics, primarily related to sound privacy [91]. Hence, for a building to be comfortable and healthy for occupants, different guidelines and standards need to be im-plemented to ensure that acceptable thresholds are being met. Moreover, the application and validation of different guidelines and standards to meet IEQ parameter thresholds are neither practical nor economical. Figure 3 shows the practicality of this problem through the real IEQ guidelines in North America. ‘Bar A’ in Figure 3 shows the percentage coverage of each IEQ parameter in the reviewed guidelines. A total of 48% of the guidelines only address indoor air quality, 17% of the guidelines only address thermal comfort, and the percentages for visual com-fort and acoustic comfort are 22% and 9%. Only 4% of the guidelines consider a combina-tion of IEQ parameters simultaneously. This provides a clear picture of the issue that needs to be addressed when implementing IEQ guidelines. Either designers and construc-tors should consider multiple guidelines to avoid the problems mentioned previously or there should be more holistic solution where a combination of IEQ guidelines must be developed. Among the reviewed standards, only one, the WELL Building Standard V2, addressed different dimensions of IEQ [68]. However, the WELL Building Standard itself Figure 3. Percentages of guidelines under each IEQ parameter and energy efficiency a se sment.This review of 23 orth erican guidelines and standards indicated that the majorityare focused on only a specific parameter and do not provide impacts regarding other IEQdimensions. For instance, ASHRAE standard 55 is focused on thermal comfort [29]. Athermally comfortable indoor environ ent does not al ays indicate that other indoorparameters are within acceptable limits or that they are performing equally or better. Forinstance, a field study on a dormitory building ventilated by split air-conditioning showeda high thermal comfort (80%) rating indicated by the occupants [90]. However, whencompared against a similar naturally ventilated building with only 60% acceptance, theair contained a 1.6 times higher concentration of CO2 or poor air quality. Likewise, abuilding can achieve acceptable levels of thermal comfort but have poor acoustics. Forexample, a survey study in the United States on occupants of office buildings with radiantheating and cooling systems indicated that majority of the participants had low satisfactionwith the office acoustics, primarily related to sound privacy [91]. Hence, for a building tobe comfortable and healthy for occupants, different guidelines and standards need to beimplemented to ensure that acceptable thresholds are being met. Moreover, the applicationand validation of different guidelines and standards to meet IEQ parameter thresholds areneither practical nor economical.Energies 2025, 18, 1740 16 of 30Figure 3 shows the practicality of this problem through the real IEQ guidelines inNorth America. ‘Bar A’ in Figure 3 shows the percentage coverage of each IEQ parameterin the reviewed guidelines. A total of 48% of the guidelines only address indoor air quality,17% of the guidelines only address thermal comfort, and the percentages for visual comfortand acoustic comfort are 22% and 9%. Only 4% of the guidelines consider a combinationof IEQ parameters simultaneously. This provides a clear picture of the issue that needsto be addressed when implementing IEQ guidelines. Either designers and constructorsshould consider multiple guidelines to avoid the problems mentioned previously or thereshould be more holistic solution where a combination of IEQ guidelines must be developed.Among the reviewed standards, only one, the WELL Building Standard V2, addresseddifferent dimensions of IEQ [68]. However, the WELL Building Standard itself has a setof limitations. Firstly, it is an international standard that cannot be representative of thespecific local IEQ requirements in North America. Secondly, the standard is complex andmay only be feasible for large projects, as small organizations have a limited budget for itsapplication [92].From ‘Bar B’ in Figure 3, it can be seen that only about 21% of the guidelines andstandards considered or were combined with energy efficiency. This is a concern, since IEQparameters often compete with energy efficiency. There are a plethora of studies showingthat more energy-efficient buildings come at the cost of poor acoustics, poor visual comfort,and/or poor IAQ and vice versa. For example, in order to maintain thermal comfort inmixed-ventilated tall buildings, an additional 38% of energy is required [93]. Likewise, lowventilation rates are associated with low energy use but have been shown to trap indoorpollutants such as radon, VOCs, and carbon dioxide [94]. Increased levels of indoor airpollutants are especially common in retrofitted houses where only the envelope is improvedand the HVAC system remains the same [95].In short, this review of North American IEQ standards and guidelines indicates thefollowing limitations. Most IEQ guidelines have been developed independently and can beadopted by any form of building construction process regardless of energy efficiency. Thisis a significant gap in terms of the combined IEQ and energy efficiency target in modernbuildings. IEQ guidelines are generally based on voluntary adaptation. Therefore, pursuingenergy-efficient buildings through existing IEQ guidelines seems almost impossible in thecontext of North America.5. Building Energy Codes and Standards: Energy Efficiency and IEQBuilding energy codes and standards are policy instruments that aim to improve theenergy efficiency of buildings. This is achieved by reducing energy loads and by using moreenergy-efficient systems and equipment. They can broadly be categorized into prescriptiveand performance-based codes. Prescriptive codes define the minimum and maximumrequirements to be followed by building envelopes and systems [96]. Performance-basedcodes, on the other hand, focus on the overall performance of buildings and are neutralregarding the building system and equipment used to achieve the target rather thanfocusing individual systems and components and defining energy targets to be achieved bythe building [97]. Performance-based codes are considered more flexible than prescriptivecodes. This section of the review focuses on North American building energy codesand energy efficiency standards in relation to IEQ. The energy codes are evaluated fortheir primary focus and capacity to tackle the IEQ parameters defined in Section 3. InSection 4, the accountability of the existing North American IEQ guidelines in terms ofenergy efficiency was analyzed in-depth. This section provides a vice versa approach,where the accountability of the existing North American building energy codes in terms ofIEQ parameters is investigated.Energies 2025, 18, 1740 17 of 30A full investigation table of the building energy codes is provided in File S1 in theSupplementary Materials. Table S1 contains 18 common building energy codes available inNorth America. The sign ‘✗’ in front of a standard/code indicates that the relevant IEQparameter is not addressed or is below a ‘satisfactory level’.Energy codes mainly provide a pathway to achieve minimum energy performancegoals in practical constructions. On the other hand, energy certification programs provide aholistic pathway to achieve overall building sustainability. Figure 4 visually demonstratesthe IEQ coverage on the reviewed energy codes and standards. Overall, 50% of them donot consider IEQ at all. The rest of the 50% consider IEQ in two paths. Six (17%) energycodes and standards consider all the IEQ parameters parallel to the energy efficiency ofbuildings (ASHRAE 90.1/90.2, California Title 24, BREEAM, CASBEE, LEED, the WELLBuilding Standard [98–101]), while 33% consider one or two (not all) IEQ parameters inaddition to energy efficiency.Energies 2025, 18, x FOR PEER REVIEW 17 of 31 WELL Building Standard [98–101]), while 33% consider one or two (not all) IEQ parame-ters in addition to energy efficiency. Figure 4. Percentages of energy codes and standards based on IEQ coverage. Out of the six that consider all the IEQ parameters, four of the documents covering IEQ aspects are building energy performance certifications. Some codes, such as ASHRAE 90.1/90.2, discuss energy performance as a standalone guide. However, supplementary standards such as ASHRAE 55 and ASHRAE 60.1/60.2 can be combined with 90.1 and 90.2 to determine energy efficiency and IEQ. It was also observed that most energy codes and standards are vague about indoor environmental parameters and only define one param-eter. For instance, indoor temperature limits are often part of building standards; however, the impact on thermal comfort is not ensured. For example, the National Energy Code for Buildings in Canada defines heating (21 °C) and cooling (19 °C) temperature set points [102]. On the other hand, the BC Energy Code addresses the concerns of overheating, but other factors remain unaddressed [103]. Likewise, the complexity of the IEQ parameters and their high reliance on how occupants interact with the building systems and internal and external conditions of the building can result in poor IEQ. Post-occupancy evaluation (POE) and the use of monitored IEQ parameters is not a common requirement in the ma-jority of the building codes and standards. Numerous studies have explored and shown the advantages of performing POE for attaining improved IEQ [104]. Thus, there is need to have post-occupancy surveys be a requirement in codes to check the effectiveness of the codes and standards for different types of buildings. Another associated factor is the changing lifestyle and occupancy patterns of occupants that affect how buildings operate and the associated IEQ maintenance needs. For example, COVID-19 resulted in significant changes in occupant patterns and increased energy needs for residential buildings [105]. These changing patterns need to be incorporated into codes, and the associated IEQ needs to be investigated for different codes and standards. The development of building energy codes is often slow, with most codes revised every 3 years. However, regional codes can be extremely outdated; for example, the states of Oklahoma and South Carolina follow older versions of the International Energy Con-servation Code (2006 and 2009, respectively) [106]. Hence, the progress of codes can be out of line with actual IEQ requirements and the latest technology developments. Moreo-ver, the revision of building energy codes and standards needs keep pace with changing Figure 4. Percenta es of energy codes and standar s b sed on IEQ coverage.Out of the six that consider all the IEQ par met rs, four of the documents coveringIEQ aspects are building energy performance certificatio s. Some codes, uch as ASHRAE90.1/90.2, discuss energy performance as a standalone guide. How ver, supplem ntarystandards such s ASHRAE 55 and ASHRAE 60.1/60.2 can be combi ed with 90.1 and90.2 to determine en rgy effici nc and IEQ. It was also observed that most energy codesand standards are vague about indo r envir nmental parameters and only efine oneparameter. For instance, indoor temperature limits are often part of building standards;however, the impact on thermal comfort is not e sured. For example, the National E ergyCode for Buildings in Canada defines heating (21 ◦C) and cooling (19 ◦C) temperature setpoints [102]. On the other hand, the BC Energy Code addresses the concerns of overheating,but other factors remain unaddressed [103]. Likewise, the complexity of the IEQ parametersand their high reliance on how occupants interact with the building systems and internaland external conditions of the building can result in poor IEQ. Post-occupancy evaluation(POE) and the use of monitored IEQ parameters is not a common requirement in themajority of the building codes and standards. Numerous studies have explored and shownthe advantages of performing POE for attaining improved IEQ [104]. Thus, there is needto have post-occupancy surveys be a requirement in codes to check the effectiveness ofthe codes and standards for different types of buildings. Another associated factor is theEnergies 2025, 18, 1740 18 of 30changing lifestyle and occupancy patterns of occupants that affect how buildings operateand the associated IEQ maintenance needs. For example, COVID-19 resulted in significantchanges in occupant patterns and increased energy needs for residential buildings [105].These changing patterns need to be incorporated into codes, and the associated IEQ needsto be investigated for different codes and standards.The development of building energy codes is often slow, with most codes revisedevery 3 years. However, regional codes can be extremely outdated; for example, thestates of Oklahoma and South Carolina follow older versions of the International EnergyConservation Code (2006 and 2009, respectively) [106]. Hence, the progress of codes can beout of line with actual IEQ requirements and the latest technology developments. Moreover,the revision of building energy codes and standards needs keep pace with changing climatedemands. For instance, the recent wildfires in British Columbia (Canada) in 2022 showedincreased levels of air pollutants (PM 2.5), which are especially harmful to children [107].Extreme weather events such as higher rainfall, heat domes, and cold snaps are predictedto increase, thus further affecting the effectiveness of the existing standards in terms ofensuring a safer environment for occupants. Increasing temperatures and outdoor CO2levels increase the level of allergens infiltrating building ventilation systems [108]. In BritishColumbia alone, the heat dome of 2021 caused 691 deaths, the majority of whom wereelderly, and these deaths were associated with overheating. Some codes already considerthe changing climate and keep their occupants relatively safe under extreme climate events.A study conducted by the Pacific Northwest National Laboratory on building resiliencyenhancement showed that people residing in buildings complying with the IECC 2021update will be able to cope with heating (140%) and cold snaps (120%) more than peoplecomplying with prior codes [109]. Hence, in addition to new buildings that need to keeppace with rising demands, existing buildings need to be renovated to ensure acceptableIEQ levels under the building energy code implementation process.6. DiscussionThe two primary aspects that need to be considered in today’s sustainable buildingconstruction industry are building energy performance and indoor environmental quality.Many measures have been taken to enhance building energy efficiency due to globalclimate change and energy poverty. The level of the pursuit of building energy efficiencyhas become too significant during the last few decades. Hence, IEQ aspects have beenpushed off to a neglected level in many cases. Therefore, the investigation of existing IEQguidelines and building energy codes in terms of practical industry is vital for future codedevelopment and building stock construction. IEQ and energy efficiency cannot performwell individually, and these two aspects need to be considered together, as identified bythe above investigations.6.1. InterrelationshipsSections 4 and 5 show the strengths and weaknesses of the existing IEQ guidelinesand standards and building energy codes and standards, respectively. Some IEQ standardsand energy codes can show synergy, where an improvement in one aspect improves theother parameter. For example, an improved HVAC system under an energy performancestandard can result in better indoor air quality. Likewise, codes can encourage dependenceon daylight-responsive systems that decrease energy use and improve visual and thermalcomfort for occupants. On the other hand, conflicting parameters are also prevalent, whereimproved energy efficiency is determinantal to IEQ. Hence, it is important to consider andprioritize IEQ parameters when designing and developing energy efficiency guidelinesand practices. In terms of considering these aspects and the identified limitations of theEnergies 2025, 18, 1740 19 of 30existing guidelines, codes, and standards, the first important question that needs to beanswered is an understanding of the relationship between IEQ parameters and buildingenergy efficiency. The interrelationships and dependability between these two aspectsare demonstrated in Figure 5 based on the previous investigations into IEQ standardsand energy efficiency standards. Table 5 contains the detailed findings and informationregarding the numbered interactions/dependabilities demonstrated in Figure 5. The inter-relationships are classified using the four primary IEQ parameters identified in Section 3and two energy efficiency enhancement approaches currently used in the industry. All thebuilding energy codes and standards identified in Section 5 use these two basic approachesto enhance building energy efficiency regardless of whether they consider IEQ or not. Thetwo approaches to enhance building energy efficiency are as follows:• Approach 1: Improve the energy efficiency of equipment and appliances (e.g., HVAC,hot water systems, electrical appliances).• Approach 2: Improve the building envelope’s thermal performance by using betterinsulation and reducing the air infiltration and leakage rate for space conditioning(through airtightness).A total of 19 connections and dependabilities were identified between the IEQ param-eters and energy efficiency enhancement methods. Mostly, many of the building energycodes and IEQ guidelines consider one or two such connections, as detailed in Table 4above and in File S1, Table S1. This creates a massive gap between IEQ and the energyefficiency performance of a building in real life, causing all the practical problems discussedin the evaluated studies in Sections 4 and 5. A comprehensive building construction guideshould properly explore all these connections and consider the adverse effects on each othercaused by changing these parameters. The development of IEQ guidelines and buildingenergy codes must be conducted on the basis of these connections as a whole package,unlike the codes and guidelines investigated in Sections 4 and 5. Table 5 explains to whatextent these connections are used in the reviewed guidelines and highlights the importanceof the findings from this review.Energies 2025, 18, x FOR PEER REVIEW 19 of 31 • Approach 1: Improve the energy efficiency of equipment and appliances (e.g., HVAC, hot water systems, electrical appliances). • Approach 2: Improve the building envelope’s thermal performance by using better insulation and reducing the air infiltration and leakage rate for space conditioning (thr ugh airtightn ss). A total of 19 connections and dependabilities were ide tified between the IEQ pa-rameters and energy efficiency enhancement methods. Mostly, many of the building en-ergy codes and IEQ guidelines consider one or two such connections, as detailed in Table 4 above and in File S1, Table S1. This creates a massive gap between IEQ and the energy efficiency p rformance of a building i real life, causing all the practical problems dis-cussed in the evaluated studies in Sections 4 and 5. A comprehensive building construc-tion guide should properly explore all these connections and consider the adverse effects on each other caused by changing these parameters. The development of IEQ guidelines and building e ergy codes must be conducted on the basis of th se connectio as a hole package, unlike the codes and guidelines investigated in Sections 4 and 5. Table 5 explains to what extent these connections are used in the reviewed guidelines and highlights the importance of the findings from this review. Figure 5. Interactions between indoor environmental quality parameters and energy efficiency. Figure 5. Interactions between indoor environmental quality parameters and energy efficiency.Energies 2025, 18, 1740 20 of 30Table 5. The connections between IEQ parameters and energy efficiency enhancement methods.1HVAC system characteristics heavily change the thermal conditions and indoor temperature distribution. Therefore, building energy codes mustconsider thermal comfort when defining HVAC guidelines. On the other hand, IEQ guidelines on thermal comfort must be able to guide a rangeof HVAC systems.2 Heat recovery ventilation can cause an imbalance in the indoor air temperature, which may result in changes in thermal comfort conditions.3 Hot water systems may or may not impact thermal comfort indirectly. Based on the location of heat tanks, pipes, and other equipment, thelocalized thermal comfort levels can be influenced.4 The indoor conditioning rate (heating/cooling) may vary based on the energy source and demand if alternative energy sources are used (e.g., ifsolar PV or geothermal heating are to be used as per the energy code, the effect on the thermal comfort evaluation is required)5The thermal envelope insulation capacity directly affects the heat retained inside and the heating/cooling loads. Most energy codes only considerthe insulation capacity. Detailed occupant thermal comfort modelling needs to be integrated for these to identify the effect on TC by theenvelope’s insulation levels.6 Heat leakage and the heat-retaining capacity of the thermal envelope are parameters that directly control thermal comfort. None of the reviewedNorth American energy codes considers this connection with airtightness/infiltration modelling for the variation in indoor TC.7 Windows, doors, roofs, floors, and wall materials vary in terms of thermal transmission values, and the inside thermal conditions will reactaccordingly. The effect of the envelope materials on TC must be integrated into performance-based energy codes.8The window-to-wall ratio is a main factor when calculating the mean radiant temperature inside. Other than a small handful of energy codes,many still consider the dry bulb temperature in their design guidelines. The mean radiant-temperature-based operative temperature must beused if TC is to be considered.9Based on the HVAC air distribution methods, IAQ can be affected significantly. This aspect is considered in most of the building energy codes,unlike the TC-related factors. The detailed HVAC system designs actually consider IAQ to a very satisfactory level in most of the current NorthAmerican building energy codes.10 Heat recovery ventilation can affect IAQ by affecting humidity and heat recovery levels. This is an important finding that is not considered to asatisfactory level in many energy codes. However, the effect of this mainly affects TC, while IAQ suffers a little.11Infiltration and natural ventilation rates can drastically modify the air-changing cycle. However, airtight envelopes can prevent particulatepollution from entering the building. The infiltration effect of modelling on IAQ is not considered to a satisfactory level in many energy codes.This needs to be incorporated into HVAC design as an additional air pollution intake. Depending on the geographical location, this can have asignificant impact on IAQ.12Passive cooling or natural lighting spaces can affect IAQ with undesired particulate pollution inside. These passive cooling aspects are mainlydiscussed in the energy efficiency certification standards rather than in the traditional energy codes. These certifications consider IAQ to asatisfactory level. However, most of the North American traditional energy codes must adopt these evaluations if they are to recommend passivecooling and natural lighting through open space.13 Visual comfort directly depends on the lighting system and smart light control techniques. Most of the lighting guidelines consider VC. If theenergy codes are to use already existing lighting guidelines, this connection is considered automatically.14Natural lighting is a direct consequence of the envelope elements, such as glass surfaces, which depend on the window-to-wall ratio. This is aseriously neglected factor in most traditional energy codes, where glass/transparent envelope surfaces are reduced to save energy. The envelopedesign must compensate for VC adequately.15 Natural lighting can be reduced or enhanced based on the number of open-area surface elements in the building envelope. This connection isconsidered in the energy certification standards to a satisfactory level.16HVAC system duct fans, blowers, heaters, and furnaces are one of the primary sound disturbances in residential buildings. This is a mostlyneglected connection in many North American building energy codes itself. However, several AC guidelines are used in some cases on top of theenergy code to fix this. If integrated guidelines are to be developed, these issues will be fixed without having to adopt multiple guidelines forenergy and IEQ.17The soundproof characteristics of the thermal envelope materials can enhance or decrease the level of indoor audio disturbances.Building-envelope-based AC modelling is not considered in commercial building energy codes itself as an integrated part. Some codes doconsider this connection by adopting third-party AC guidelines. However, this is an addition to the envelope rather than being a part of theoriginal envelope design.18An effective window area of a building can change the sound penetration characteristics of the building (e.g., glass is less effective than insulatedwalls). A similar connection to ‘17’ but related to windows and fenestration. This is a critical connection to consider, depending on thegeolocation of the building.19Opening areas are direct sources of outdoor sound penetrations to the inside of a building’s living spaces. Only the energy certification standardsconsider this connection to a satisfactory level. It is a very important factor to consider in urban developments if passive designs arebeing pursued.Among the various relationships observed in the literature, the role of HVAC systemsstands out as one of the most critical. Changes in HVAC systems directly influence airchange rates and the mode of indoor air circulation. The impact directly affects IAQ invarious ways, such as increases in particulate pollutant levels due to fewer air changes,the indoor air velocity, and clean air distribution and circulation. HVAC systems mayfurther affect indoor air temperature values based on the energy systems’ cooling andEnergies 2025, 18, 1740 21 of 30heating set points. Indoor conditions can be too warm or cold, negatively influencingthermal comfort. Thermal envelope designs directly affect indoor thermal conditions. Mostmodern envelopes are designed to retain heat inside with minimal losses. With sealed-envelope designs and fewer infiltrations, indoor environments can become too warm andhighly humid, resulting in a lack of thermal comfort conditions for occupants. The thermalenvelope also affects the visual comfort of occupants when the envelope is designed tosave and retain indoor heat. A lack of glass surfaces (windows, door glasses, and glasswalls) may result in poor daylighting conditions and thereby reduce visual comfort.Table 5 above presents some of the major findings from this review. All these19 connections were identified during the in-depth investigations in Sections 4 and 5.It is critical that leading energy codes and standards attempt to integrate at least severalof these connections into their design. If not, the energy code implementation processcan influence all four IEQ parameters in various pathways, creating unacceptable IEQ foroccupants.6.2. Implications and Future DirectionsAs the above investigation proves, the lack of a connection between energy efficiencycodes and existing IEQ guidelines is critical. Future-proofing existing energy codes andIEQ is essential considering emerging technologies and materials and the changing cli-mate. There is a need for an integrated approach with all four IEQ parameters, energyaspects, and GHG emissions. In addition, the approach must be developed considering‘occupant-centric’ concepts rather than the financial-goals-centric perspective. In the litera-ture, two such models, ‘TAIL’ and ‘IEQ compass’, developed in the European context, areavailable, which combine some of the above aspects. ‘TAIL’ was developed as a part of theEuropean energy certification method under the ALDREN project [110]. The TAIL frame-work uses a rating system to evaluate all the IEQ parameters simultaneously. However,TAIL does not actively consider building energy efficiency or energy performance.The second combined IEQ assessment method is ‘IEQ compass’ [111]. IEQ compassis a tool developed to evaluate potential IAQ, thermal comfort, and visual and acousticcomfort levels [111]. The tool generates results without considering user influences, unlikeother survey-based IEQ evaluations. IEQ compass can deliver an overall IEQ parame-ter/label for the considered building after assigning a weight for each IEQ parameter. TheIEQ labelling process uses a letter-based ranking system and a color-coded score for thebuilding design. The results were generated in this model by using a case study build-ing through building information modelling [111]. This IEQ compass tool has paved asignificant pathway towards future-proofing IEQ guidelines and energy efficiency codes.However, the IEQ compass tool has some considerable limitations in terms of its overallIEQ evaluation. The main drawback of this model is that it does not use user inputs andinfluences. Such an approach could mislead the final ranking results compared to theactual IEQ conditions of the physical building. Particularly for residential buildings, userinfluences and inputs are very important. Moreover, this tool gives the four primary IEQparameters equal importance while calculating the overall IEQ rank. However, usingparameters with equal importance without user influence can be further misleading interms of the final performance of the buildings. With the availability of the data and otherrelevant information, ‘IEQ compass’ attempted an interesting approach to define an overallIEQ parameter of buildings. It provides solid ground for further improved versions toevaluate overall IEQ and energy efficiency. Figure 6 shows the IEQ compass label ratingswith the performance score of the building.Energies 2025, 18, 1740 22 of 30ergies 2025, 18, x FOR PEER REVIEW 23 of 31 Figure 6. IEQ compass rating system [111]. In addition, the European Union’s Energy Performance of Buildings Directive (EPBD) actively pursues the importance of combined energy efficiency and IEQ as a whole eval-uation metric for buildings [112]. However, in North America, similar pathways are lack-ing. In particular, the harsh cold climates in North America are ideal research grounds for investigating such a combined platform with energy consumption and IEQ of future building stock. On the other hand, the harsh cold climate conditions are the leading reason for this lack of guidelines in North America. The conservation of energy and mitigation of GHG emissions have been the primary target for many decades. Hence, the considera-tion of IEQ has been under the shadow of energy efficiency. As a result, such integrated tools from a North American perspective are not readily available, unlike in Europe. Moreover, the European regions have started pushing the requirements of IEQ as man-dates and law, unlike in many North American regions. Therefore, the lack of a combined implementation for energy efficiency and IEQ is further lagging behind in North America. However, global warming effects and rapidly changing climate situations call for such initiatives now. Moreover, the usefulness of such pathways for North America will help the building sector move towards smart buildings and smart cities in regions with a cold climate. More data can be monitored and accumulated through smart building instrumentations for IEQ parameters. Therefore, dynamic IEQ scales can be developed and integrated with build-ing energy performance to deliver real-time overall building performance data. Figure 7 shows what such an integration would look like when combined performance scales are developed for energy efficiency and IEQ. Hypothetical values are shown in this figure. The proposed integration is shown for the IEQ index with the EnerGuide energy rating system for homes. EnerGuide is a commonly used energy rating scale in Canadian houses, particularly for small residential buildings [113]. The EnerGuide rating system is used here as a sample, since it is nationally recognized across all the provinces in Canada. The United States also has a similar energy rating system for homes called the HERs index [114]. The development of a combined index will require extensive data collection on local construction practices, surveys from occupants and the construction industry, the consid-eration of suitable weighting and aggregation methods, and testing on actual case study i . I ti t [ ].I iti , t i ’ f f il i s irective ( )ti l t e i portance of combined energy efficiency and IEQ as a whole valua-tion metric for buildings [112]. Howev r, in North America, similar pathways are lacking.I particular, the harsh cold climates in North America are ideal research grounds for inves-tigatin such a combined platform with energy consumption and IEQ of future buildingstock. On the other and, the harsh cold climate conditions are the leading reason for thislack of guidelines in North America. The conservation of energy and mitigation of GHGemissions have been the primary target for many decades. Hence, the consideration ofIEQ has been under the shadow of energy efficiency. As a result, such integrated toolsfrom a North American perspective are not readily available, unlike in Europe. Moreover,the European regions have started pushing the requirements of IEQ as mandates and law,unlike in many North American regions. Therefore, the lack of a combined implementationfor energy efficiency and IEQ is further lagging behind in North America. However, globalwarming effects and rapidly changing climate situations call for such initiatives now.Moreover, the usefulness of such pathways for North America will help the buildingsector move towards smart buildings and smart cities in regions with a cold climate.More data can be monitored and accumulated through smart building instru entationsfor IEQ parameters. Therefore, dynamic IEQ scales can be developed and integratedwith building energy performance to deliver real-time overall building performance data.Figure 7 shows what such an integration would look like when co bined performancescales are developed for energy efficiency and IEQ. Hypothetical values are shown inthis figure. The proposed integration is shown for the IEQ index with the EnerGuideenergy rating system for homes. EnerGuide is a commonly used energy rating scale inCanadian houses, particularly for small residential buildings [113]. The EnerGuide ratingsystem is used here as a sample, since it is nationally recognized across all the provincesin Canada. The United States also has a similar energy rating system for homes calledthe HERs index [114]. The development of a combined index will require extensive datacollection on local construction practices, surveys from occupants and the constructionindustry, the consideration of suitable weighting and aggregation methods, and testingon actual case study buildings. Performance verification based on sensor-monitored dataEnergies 2025, 18, 1740 23 of 30as well as post-occupancy surveys would ensure that buildings meet the desired IEQand energy standards. In addition, the developed performance scale should be flexibleenough to consider adaptive strategies, such as increased cooling load requirements undera changing climate and the latest trends in building technologies and materials. Lastly, theimportance of different occupant needs and behaviors should be a central consideration ofthis performance framework. Such an integrated model would massively benefit buildingpolicy, mandate, and regulation developers, government authorities, building constructors,and building designers. A balanced performance in terms of both energy efficiency andindoor environmental quality levels would improve the well-being and health of NorthAmerican dwellers.Energies 2025, 18, x FOR PEER REVIEW 24 of 31 buildings. Performance verification based on sensor-monitored data as well as post-occu-pancy surveys would ensure that buildings meet the desire IEQ and energy tandards. I addition, the eveloped performance scale should be flexible enough t consider adap-tive strategies, such as incr ased cooling load requirements u der changing climate and the latest trends in building technologies and materials. Lastly, the importance of different occup t nee s and behaviors should be a central consi eration of this performance fram w k. Such an integ ated model would massively benefit building policy, man ate, and regulation developers, government authorities, building constr ctors, and b ilding designers. A balanc d performance in ter s of both energy effici cy and indoor envi-ronmental quality levels wou d improve the well-being and health of North American dw llers. Figure 7. Proposed integration of EnerGuide rating with the indoor environmental quality index. * This house indicates the case study reference house design. 7. Conclusions Poor IEQ can cause various health-related problems for occupants, including, but not limited to, sick building syndrome, a lack of sleep, and a reduction in working efficiency. Understanding and improving IEQ is a complex process, and the recent changes in occu-pant lifestyle patterns (for example, increased hours spent working from home following COVID-19), the changing climate, and an aging population have made IEQ pertinent for a sustainable future and for the health, satisfaction, and well-being of occupants. This re-view was conducted to identify the current status of IEQ standards/policies, evaluate the Figure 7. Proposed integratio of er i e r ti it t i r i t l lit i .This house indicates the case study reference house design.7. ConclusionsPoor IEQ can cause various health-related problems for occupants, including, but notlimited to, sick building syndrome, a lack of sleep, and a reduction in working efficiency.Understanding and improving IEQ is a complex process, and the recent changes in occu-pant lifestyle patterns (for example, increased hours spent working from home followingCOVID-19), the changing climate, and an aging population have made IEQ pertinent for asustainable future and for the health, satisfaction, and well-being of occupants. This reviewwas conducted to identify the current status of IEQ standards/policies, evaluate the overallIEQ of buildings, examine IEQ-related data, and examine the extent to which buildingEnergies 2025, 18, 1740 24 of 30energy codes and green building standards account for IEQ parameters. The scope of thereview was kept within the North American region when evaluating the energy codes andIEQ guidelines.As a result, the current relationship between IEQ and building energy codes andstandards were explored. This review identified 19 different interactions and dependentrelationships between the primary IEQ parameters and energy efficiency enhancementmethods. It was found that most of the reviewed IEQ standards and guidelines lack compre-hensive methods to cover all IEQ parameters comprehensively. Designers and constructorsmay have to use multiple standards to achieve satisfactory levels of IEQ. Moreover, theseIEQ guidelines generally exclude energy efficiency parameters. Hence, building energycodes must be used in addition to IEQ guidelines. A few energy certification standards,such as LEED, CASBEE, and the WELL Building Standards V2, discuss all four IEQ param-eters in parallel with energy efficiency practices. However, their implementation requiresexpertise, and they are often not possible to implement by small construction companies.Moreover, these certifications are based on voluntary adaptation and are not a law ormandate. IEQ parameter values and energy efficiency codes can be in synergy or in conflictdepending upon the type of codes, buildings, and users. From the perspective of buildingenergy codes, many fail to evaluate the identified 19 connections. Several traditional build-ing energy codes consider some connections to IEQ, but it is not feasible enough to providea balanced IEQ for occupants. Hence, there is a need to revise the generic North Americanbuilding energy codes and IEQ guidelines to consider complex interactions.The most viable and long-term solution is to update and future-proof the currentlyavailable energy codes and IEQ guidelines through a combined platform. If an integrationis achieved between IEQ guidelines and building energy codes by considering all theabove-identified 19 connections, the buildings developed through the combined platformwill provide a perfect balance in terms of IEQ and energy efficiency. Based on the findingsof this review, it is proposed to develop a model for the North American regions in whichIEQ and energy efficiency are represented on a benchmark scale. As the initial steps,research-based methods should be explored using European models, such as TAIL’ and‘IEQ compass’, as starting points. As the proposed scale is updated and improved withdata collection, surveys, expert opinions, and real-world case studies, more sustainable andhealthy buildings will be possible. Likewise, future building energy codes, IEQ standards,and guidelines can be connected in a single platform to each of the ultimate sustainabilitygoals of future building designs. An occupant-centric, human health and well-being-focused, energy-efficient, and sustainable building stock could significantly change theNorth American construction industry and occupant lifestyle.Supplementary Materials: The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/en18071740/s1, File S1, Table S1: Building energy codes/standardsand their involvement in IEQ-North American perspective; File S2: PRISMA 2020 Checklist.Author Contributions: Conceptualization, I.P.; methodology, I.P. and A.R.; formal analysis, I.P.and A.R.; investigation, I.P. and A.R.; writing—original draft preparation, I.P.; writing—reviewand editing, A.R., K.H. and R.S.; visualization, I.P. and A.R.; supervision, K.H. and R.S.; projectadministration, K.H. and R.S.; funding acquisition, K.H. and R.S. All authors have read and agreed tothe published version of the manuscript.Funding: This research was funded by MITACS Accelerate Canada and FortisBC (Grant ID:GR032421) and “The APC was funded by the Special Issue Journal Energies at a 100% discount”.Data Availability Statement: The original contributions presented in this study are included in thearticle/Supplementary Material. Further inquiries can be directed to the corresponding author.Energies 2025, 18, 1740 25 of 30Acknowledgments: The authors’ grateful acknowledgment goes to the funding partners for theirsupport and other opportunities provided through the University of British Columbia.Conflicts of Interest: The authors declare no conflicts of interest.AbbreviationsThe following abbreviations are used in this manuscript:IEQ Indoor environmental qualityGHG Greenhouse gasIAQ Indoor air qualitySBS Sick building syndromeLEED Leadership in Energy and Environmental DesignWHO World Health OrganizationTC Thermal comfortPMV Predicted mean votePPD Predicted percentage of dissatisfactionASHRAE American Society of Heating, Refrigerating, and Air-Conditioning EngineersHVAC Heating, ventilation, and air-conditioningPM Particulate matterEPA Environmental Protection AgencyVC Visual comfortIESNA Illuminating Engineering Society of North AmericaAC Acoustic comfortUDI Useful daylight illuminanceDA Daylight anatomyDF Daylight factorReferences1. 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Article
eng
Reviewed
Vancouver : University of British Columbia Library
Multidisciplinary Digital Publishing Institute
CC BY 4.0
Faculty
Researcher
indoor environmental quality (IEQ)
thermal comfort
indoor air quality (IAQ)
acoustic comfort
visual comfort
building energy efficiency
green building standards
Combining Energy Performance and Indoor Environmental Quality (IEQ) in Buildings : A Systematic Review on Common IEQ Guidelines and Energy Codes in North America
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