Indoor Air Quality: Health, Productivity, and Economic Gains

Abstract: This paper reviews scientific literature on the relationship between IAQ, ventilation, and costs, emphasizing the adverse effects of poor IAQ and the benefits of effective ventilation. It aims to advance discussions on strategic IAQ management and the role of ventilation in promoting healthy, energy-efficient, and productive indoor environments.

Keywords: Indoor air quality, energy efficiency, productivity, well-being, cost-benefit of ventilation

Introduction

Individuals spend the majority of their time indoors, where poor indoor air quality (IAQ) significantly affects health, well-being, and productivity [1,2]. The COVID-19 pandemic has emphasized the importance of ventilation not only for comfort but also IAQ, infection control, and overall occupant health, underscoring the need for integrated approaches to address health, safety, and sustainability [3]. With buildings accounting for 40% of final energy consumption in Europe[4], there is growing pressure to decarbonize. However, energy efficiency measures such as reducing outdoor air intake or tightening building envelopes may lead to insufficient ventilation and adversely affect IAQ.

Ensuring adequate ventilation has been shown to enhance cognitive performance, reduce absenteeism, and improve occupant satisfaction [5], emphasizing the broad advantages of effective IAQ management. Furthermore, strategic investments in ventilation systems can yield significant health benefits while simultaneously offering energy savings and productivity gains [6,7]. Despite these benefits, such improvements often involve considerable costs, necessitating a careful evaluation of their economic feasibility.

This study reviews the multifaceted significance of IAQ and its impacts on building occupants as documented in scientific literature. Specifically, it examines the relationship between IAQ, ventilation, and energy usage, highlighting the adverse effects of poor IAQ and the benefits of effective ventilation. Additionally, it focuses on studies addressing the cost-benefit aspect of IAQ management and ventilation strategies, providing a comprehensive perspective on their feasibility and impact.

Implications of inadequate indoor air quality

Certain indoor pollutants are known to pose health risks: For example, formaldehyde and aromatic compounds like benzene are frequently observed across various built environments [8]. Formaldehyde, often emitted by building materials, can reach significantly higher concentrations indoors than outdoors, particularly following new construction or renovations. Acute exposure may cause irritation of the eyes, nose, and throat, trigger respiratory symptoms and exacerbate asthma [9]. Similarly, ozone from both indoor and outdoor sources can irritate respiratory tissues, underscoring the importance of pollutant control.

Inadequate ventilation exacerbates these issues by allowing pollutants to accumulate and increasing the risk of airborne disease transmission [10,11]. Inadequate ventilation often results in elevated levels of CO₂ – emitted  by occupants – which have been linked to headaches, fatigue, and reduced cognitive performance [12]. Poor IAQ and ventilation are also believed to cause the so called “sick building syndrome” (SBS), characterized by symptoms like headaches and respiratory discomfort. These often resolve once individuals leave the building [13].

The consequences of poor IAQ extend beyond health, significantly affecting productivity through absenteeism and presenteeism – reduced workplace efficiency caused by discomfort and illness [14]. Minor respiratory conditions, such as sinusitis, asthma, and allergic rhinitis are linked to increased sick days [15]. These effects are particularly pronounced in settings like offices and schools, where occupants spend extended periods indoors and where ventilation quality directly impacts both health outcomes and overall performance.Improving air quality in these settings has been shown to effectively mitigate these issues, enhancing both health outcomes and overall performance, as discussed below.

Offices

An abundance of literature reports that enhancing indoor air quality through adequate ventilation can significantly improve occupant well-being and productivity in office settings. Ventilation rates of to up to 20 liters per second (L/s) per person have been shown to mitigate SBS symptoms [16]. A meta-analysis revealed that lower ventilation rates (2.5 L/s per person) were linked to increased adverse health effects and noticeable productivity declines compared to higher ventilation rates (30 L/s per person) [17].

Building on this premise, Wargocki and Wyon [18] investigated the effects of varying ventilation rates (3, 10, and 30 L/s per person) on perceived air quality, SBS symptoms, and productivity. Their findings demonstrate a linear relationship between higher ventilation rates and reduced dissatisfaction with air quality, fewer symptoms of dryness in the mouth and throat, and improved cognitive clarity. Notably, office task performance improved by 1.7% with each doubling of airflow rate, highlighting the tangible benefits of enhanced ventilation.

Similar studies confirm the link between increased outdoor air ventilation rates and enhanced productivity and cognitive performance. For instance, cognitive improvements of up to 101% have been reported as the outdoor air ventilation rate was doubled [19]. Furthermore, a 26.4% rise in cognitive function among occupants in LEED (Leadership in Energy and Environmental Design)-certified buildings than in non-certified buildings was also reported [20]. Performance gains from increased ventilation are most significant in the range of 6 to 10 L/s per person and greatly diminish when ventilation rate goes above 45 L/s per person [21].

Elevated indoor CO₂ levels, indicative of inadequate ventilation, have been associated with reduced work performance and increased health symptoms [22,23]. Moderate CO₂ concentrations (~1000 ppm compared to ~600 ppm) significantly impair decision-making performance with sharper declines observed above 2500 ppm. Furthermore, exposure to damp indoor environments is linked to respiratory illnesses and infections. Interventions targeting dampness and mold not only improved performance but also reduced occupant-reported symptoms and absenteeism [24,25]. Enhanced IAQ measures – including ventilation, filtration, and moisture control – are estimated to decrease sick leave due to infectious diseases by 9 to 20% [26].

Schools

Numerous studies highlight children’s heightened susceptibility to environmental pollutants, influenced by both physiological and behavioral factors. Compared to adults, children breathe more air relative to their body weight, and their developing tissues and organs are particularly vulnerable to damage [27]. Given that children spend a significant portion of their day in schools, maintaining high indoor environmental quality in these settings is crucial.

However, classroom indoor air quality is often poorer than in other indoor environments, such as homes or offices, primarily due to higher occupancy density and duration. Numerous studies have reported on the adverse effects of inadequate ventilation and elevated contaminant levels on health and learning outcomes in educational environments [28–31]. For instance, increasingventilation rates to 15 L/s per person in elementary schools has been estimated to reduce illness-related absences by 11 to 17% [32]. A significant relationship between classroom ventilation rate and academic performance has been documented, with higher outdoor air supply rate enhancing cognitive performance: Faster task completion among 10 to 12-year-old children [18] and improved mathematics test scores [33] illustrates the tangible benefits of better ventilation.

Furthermore, maintaining indoor CO₂ levels below 1000 ppm is particularly important. Studies link lower CO₂ concentrations to improved response times, accuracy, and attendance among primary school students [34–36]. These findings emphasize the critical role of superior IAQ in fostering both health and academic success.

Overall, the evidence strongly supports that superior IAQ provides both tangible, such as enhanced performance and reduced absenteeism, and intangible benefits, including improved well-being and comfort. This raises a key question: what are the costs of achieving IAQ improvement, and how do these compare to the benefits?

Cost-benefit

The return on investment (ROI) for IAQ improvements encompasses both direct and indirect benefits. Enhanced IAQ contributes to increased property value, reduced healthcare expenses, and enhanced workforce productivity, making it a critical component of building management strategies. Studies consistently demonstrate that the economic benefits of superior IAQ far exceed associated costs. For instance, increasing outdoor air ventilation rates from 12 to 24 L/s per person resulted in net annual savings of 400 USD per employee, offsetting ventilation costs [25]. Similarly, annual benefits from enhanced IAQ often exceed energy and maintenance costs by a factor of 10, with payback periods under four months [37].

A study conducted for US office buildings estimated that enhanced environments could yield annual economic benefits ranging from 5 to 75 billion USD, primarily due to improved health [38]. Additionally, raising minimum ventilation rates above 8 L/s per person could generate economic benefits between 13 billion and 38 billion USD in US office buildings, far exceeding energy costs [39]. Furthermore, simulation studies suggest that IAQ enhancements can deliver benefits up to 60 times greater than their costs, with payback periods of averaging two years [40]. Lastly, practical case studies show that doubling outdoor air supply rate reduced sick leave by 10% and improved productivity by 1.5%, demonstrating how relatively small changes can lead to significant benefits [41].

In addition to these findings, IAQ improvements contribute to broader operational and financial advantages, especially when employee productivity and salaries are considered. For example, increasing ventilation beyond recommended values added less than 40 USD annually in energy costs per person while boosting productivity by 8%, equating to 6,500 USD per office worker and 15,500 USD per manager [42]. Such results emphasize the cost-efficiency of IAQ investments, where minimal operational costs lead to substantial returns. Furthermore, studies show that tenants are willing to pay premiums for enhanced IAQ [43,44], and that certified buildings often command higher market values [44,45].

Despite these compelling benefits, the building industry faces significant challenges in prioritizing IAQ investments. Key barriers include misconceptions about ROI and insufficient financial analysis during the design and operational phases [46]. Although there has been a growing focus on IAQ monitoring in recent Energy Performance of Buildings Directive (EBPD) [4], regulatory pressure in general remains limited. Additionally, health and productivity benefits are often excluded from traditional cost assessments, undermining their perceived value. Lastly, although the benefits of improved comfort, health, and productivity are significant, comprehensive measurement and benchmarking are limited due to a lack of well-defined, widely accepted metrics.

Conclusion

This review highlights the pivotal role of IAQ in promoting health, enhancing productivity, and driving economic performance. Inadequate IAQ, often resulting from insufficient ventilation, negatively affects cognitive function, exacerbates health issues, increases absenteeism, and imposes significant economic costs. Conversely, improvements in IAQ are associated with enhanced task performance, better health outcomes, reduced illness-related absences, and measurable cost savings.

The findings suggest that IAQ improvements can represent a highly cost-effective strategy, with potential economic benefits that could exceed the costs by a factor of up to 60. Additionally, the return period for investments in IAQ enhancements is often reported to be less than two years, depending on the specific circumstances. Strengthened regulatory frameworks could drive widespread adoption, ensuring that IAQ measures are implemented consistently and effectively, rather than relying solely on voluntary actions. Such measures would deliver substantial benefits not only to individual building occupants but also to society as a whole, contributing to healthier, more productive, and economically sustainable environments.

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