While outdoor air pollution captures headlines around the world, indoor air quality (IAQ) continues to be overlooked. Meanwhile, pollution inside buildings has a wide-ranging impact on our health and mental performance.
Understanding the problem
Day-to-day inhalation of common indoor pollutants causes fatigue, headaches, and impaired cognitive function, such as difficulty concentrating. Poorly ventilated spaces also create “unhealthy buildings” in which viruses spread more easily, particularly during the winter months. Studies show that when our bodies work harder to process irritants in the air, we become more susceptible to infections.
Longer term, breathing poor-quality indoor air is linked to respiratory disease, heart conditions, and cancer risk. There is also growing evidence of indoor air pollution contributing to diabetes and dementia. In 2020, indoor air pollution caused around 3.2 million premature deaths worldwide, compared to 3.5 million deaths linked to outdoor air pollution, according to a 2022 report by the World Health Organization (WHO).
“Limited understanding of the impact of IAQ has been part of the problem for many years,” explains Maria Garcia, Director at Savills Sustainability Consultancy. “Global scientific research and government attention has historically been more focused on combatting air pollution outside,” she adds. Of the peer-reviewed articles published in the past five years that looked at air quality, just 15% focused on indoor air.
Total number of peer-reviewed research articles in the past five years
Source: Savills Research using Nature.com. Time period: 30 October 2019 – 01 November 2024
Since the pandemic, which highlighted the need for good indoor ventilation, the focus has started to shift. And yet, despite calls for stricter, legally enforceable IAQ standards to protect public health, progress has been slow. The onus has largely been on building owners and operators to improve standards voluntarily. “Innovative technological solutions and private demand for improved indoor air quality are generally moving more swiftly than regulatory mandates,” notes Garcia.
What affects indoor air quality?
IAQ is influenced by multiple factors, including ventilation, temperature, humidity, maintenance of air conditioning infrastructure, and outdoor air quality. Indoor pollutants that affect health include particulate matter, of which PM2.5 is the most harmful. Owing to its size, PM2.5 can penetrate deep into our lungs and soft tissue and cause long-term damage. Carbon dioxide (CO₂) is also key and is often used as a proxy for ventilation. Studies have shown that in warmer temperatures, CO₂ concentrations can interact with other air pollutants, further decreasing air quality.
Volatile organic compounds (VOCs), commonly found in paints, building materials, and fabrics, are another major pollutant. These chemicals can cause headaches and fatigue, as well as long-term health issues. Research has shown that VOC concentrations are significantly higher in modern buildings due to increased usage in construction over the past three decades. Moreover, modern, energy-efficient designs can also trap VOCs inside, unlike older, less energy-efficient buildings that may have better natural ventilation.
The air outside buildings also affects what will be breathed indoors, so while buildings with more natural ventilation reduce the risk of chemical and particulate build-up for occupants, excellent air tightness is important to preventing outdoor air pollution from seeping inside.
Indoor air quality certifications are playing a key role
Around the world, people are waking up to the vital importance of indoor air quality. This is in part due to the amount of time we spend inside buildings, with people in industrialised nations spending an average of 80 – 90% of their time indoors.
For a growing number of us, buildings are becoming a refuge from the outdoor environment, with its extreme heat during the summer and high outdoor air pollution. A 2024 report by Swiss air quality organisation IQAir revealed that only seven countries meet WHO outdoor air quality standards, with air pollution in India, Pakistan, China, and Mexico reaching the most hazardous levels.
Voluntary IAQ certifications offer occupants peace of mind for many offices, hotels, and residential developments. Building certifications such as WELL, RESET, and Fitwel are designed to prioritise indoor air for occupier health, productivity, and comfort via monitoring and improvement measures. Often, these certifications rely on smart property technology to monitor, manage, and improve IAQ in buildings.
Number of buildings with IAQ certifications by country & by country per capita
Source: Savills Research using WELL, RESET, and Fitwel project directories.
According to Savills research, the US has more IAQ-certified buildings than any other country. This is partly due to cultural expectations regarding air conditioning and indoor comfort. In the context of high office vacancy rates in some markets, landlords also use IAQ certifications to differentiate buildings at the prime end. For employers in the most polluted US cities, such as Los Angeles and New York, clean indoor air is an advantage in the war for talent.
Beyond the US, IAQ certifications are most prevalent in countries with the most dangerous levels of outdoor air pollution. In China, Mexico, and India, filtered air inside prime offices and luxury hotels can be 10 times cleaner than outside. Canada, Australia, and parts of southern Europe also intermittently have some of the most polluted air in the world due to wildfires, with these regions attracting increasing numbers of buildings with voluntary IAQ certifications.
In countries with overall good to moderate outdoor air quality, some cities see a concentration of landlords and occupiers seeking to improve IAQ. In London, for example, where air pollution is around double the WHO limits, indoor air quality certifications are increasingly popular at the prime end. Cities seeing a strong trend toward healthy buildings that prioritise wellbeing also have more IAQ certifications, for example, in Amsterdam and Stockholm.
Global IAQ certifications by building type
Source: Savills Research using WELL, RESET, and Fitwel project directories.
Globally, office, retail, and leisure buildings account for 84% of IAQ certifications. There is strong regional variance, with offices making up 87% of all IAQ certified buildings in India (versus a 34% global average) and retail and leisure accounting for most IAQ certifications in North America. The UAE leads the world in IAQ certifications for residential properties.
IAQ certifications in public settings lag far behind, with education and childcare (4%), healthcare (2%), and other public buildings (1%) having significantly less dedicated monitoring and improvement regimes across all regions. In particular, childcare and certain education settings merit more attention as children are more vulnerable to the effects of poor indoor air quality.
Healthier air, healthier future
Good indoor air standards are essential for people’s comfort, performance, and health. While the rise of IAQ certifications and advances in property technology are raising standards for many, urgent attention from policymakers is vital to ensuring that more of society breathes healthier air.
