15 April 2026
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Emma-Louise Bennett, Sales Support Engineer at Clivet UK, discusses why indoor air quality (IAQ) must be at the forefront of modern ventilation design.
Indoor air quality (IAQ) has become one of the most prominent topics in building services, and rightly so. Increased awareness, tighter regulations and more energy-efficient buildings have all placed greater emphasis on how ventilation systems are designed, installed and maintained. Developments such as the introduction of Awaab’s Law have brought the consequences of poor indoor environments into sharp focus, reinforcing the need to take ventilation design seriously from the outset rather than relying on remedial action later. Having recently completed both domestic and commercial ventilation training myself, I have become much more aware of the complexities of ventilation design, particularly when trying to balance energy efficiency, comfort and IAQ. Even small compromises in design or installation can have a noticeable impact, especially in high-density or inner-city projects where natural ventilation options are limited.
This raises an important question for the industry: “Are we still designing ventilation systems to meet minimum requirements, or are we designing them to genuinely provide healthy indoor environments?"
Designing for airflow vs designing for air quality
A topic I keep hearing in conversations across the industry is the difference between designing for airflow and designing for actual IAQ. Compliance has traditionally focused on achieving minimum ventilation rates, but it seems this does not always mean occupants experience healthy air once the building is in use.
Guidance such as BS 40102-1 is starting to move the focus towards measurable indoor environmental quality, encouraging monitoring and verification rather than relying only on design calculations. Despite this, adoption still feels slow.
During recent CPD sessions delivered by Mike Harrichand of Sabiana, one of the key messages was that IAQ is still not always at the forefront of consultants’ minds when ventilation systems are designed. Greater attention is often given to capacity, energy targets and space constraints, with air quality considered later in the process.
Nathan Wood of Farmwood Ltd has also highlighted the gap between UK air quality limits and World Health Organisation guidance, suggesting that buildings designed to current standards may still expose occupants to pollutant levels that are not ideal from a health perspective. With more guidance now around sick vs healthy buildings, this issue is becoming harder to ignore.
Urban environments and the growing IAQ challenge
The challenge becomes even greater in dense urban environments, where external air quality can be poor and natural ventilation is often not a realistic option. Pollutants such as PM2.5, nitrogen dioxide and volatile organic compounds are now widely recognised as key contributors to poor IAQ, particularly in cities where traffic and industrial activity increase background pollution levels.
Examples discussed during Sabiana’s IAQ CPD showed that in heavily polluted environments outdoor PM2.5 levels can exceed 100 µg/m³, meaning even ePM2.5 90% Efficiency Filters on AHUs may not be enough without careful system design.
This is especially true in high-density residential buildings. Dave Clarke of Clarke Talbot Renewables points out that in co-living environments, particularly in cities such as London, windows cannot always be relied upon for ventilation due to noise pollution. In these cases, mechanical ventilation with heat recovery becomes essential to maintain indoor air quality.
However, conventional MVHR systems alone may not always address comfort, humidity and cooling requirements, which is why there is increasing interest in more integrated solutions.
From ventilation to IAQ systems
CMYK / .ai CMYK / .ai There is growing focus on filtration and monitoring alongside airflow. An area new to me, but which I have been learning more about is electrostatic filtration, which is starting to appear more often in discussions around IAQ.
Unlike traditional mechanical filters, electrostatic systems charge airborne particles as they pass through the filter, allowing fine particulates and biological contaminants to be captured effectively without a large increase in pressure drop. This means filtration performance can be improved without significantly increasing fan energy. Some modern ventilation units incorporate this type of filtration directly within the system. For example, Clivet’s thermodynamic MVHR system ‘ELFOFresh EVO’ uses an electrostatic filtration stage alongside conventional filters, allowing pollutants such as fine dust, pollen and bacteria to be removed while maintaining efficient airflow. An alternative option would be Sabiana’s fan coil units that can also be fitted with integral electrostatic filters.
Clearly it is not enough for ventilation systems to simply move air, but to actively improve indoor environmental quality.
Integrated solutions for modern buildings
It feels like the industry is moving towards more integrated solutions rather than treating ventilation, heating and cooling as completely separate systems. In high density developments where windows may remain closed for long periods, maintaining IAQ often requires a fully mechanical approach which some manufacturers, like Clivet, are already prepared for.
Thermodynamic ventilation systems are one example of this trend. By combining heat recovery, filtration and active heating or cooling, these systems can provide continuous air renewal while also helping control temperature and humidity.
This concept is continuing to evolve, with newer systems integrating heat pump technology and domestic hot water production alongside ventilation. Products such as Clivet’s FULLNESS build on this principle, combining ventilation, filtration heating, cooling and hot water generation in a single appliance. Plant space is also becoming a limiting factor, which can affect how ventilation and IAQ systems are designed which is why the FULLNESS can be configured as two modules.
As buildings become more constrained, this type of integration is likely to play a bigger role in enabling designers to deliver both good indoor air quality and efficient building services within increasingly complex buildings.
Competence, commissioning and the performance gap
advances in technology, there is growing recognition that good indoor air quality depends heavily on correct design, installation and commissioning. While writing this article I was completing the commercial ventilation course with Greenskills Academy, and it highlighted how much detail is involved beyond basic airflow calculations.
What struck me most during training was how often systems do not perform as intended once installed, even when the design was correct. John McGregor, ventilation lecturer at the academy, commented that correcting poorly installed ventilation systems is likely to become a significant part of the industry in the coming years.
At McGregor’s suggestion I installed an IAQ monitor in my own home which quickly showed how easily air quality can deteriorate without effective ventilation.
Raising the profile of ventilation
The effort within the industry to raise the profile of ventilation itself must be celebrated. During discussions around World Ventilate Day (November 8th), Professor Cath Noakes highlighted that ventilation is not only about air quality but also about managing temperature, humidity and comfort, making it a critical part of building performance. Ventilation is important and you should be proud to be involved in it, says Simon Jones on the Air Quality Matters podcast. The industry needs pride.
IAQ can no longer be treated as a secondary consideration in building services design. Tighter regulations, greater awareness, improved technology and more challenging building environments mean ventilation systems now have to do far more than deliver minimum airflow rates.
