Ventilation


www.heatingandventilating.net


Balancing IAQ and


I


n line with the overall push to reduce the environmental impact of buildings, the design and specification of HVAC systems is often focused on operational energy use and efficiency. This is an important consideration as the UK strives to achieve Net Zero by 2050 and contribute to limiting the impact of climate change. However, the increased air-tightness that this requires means that IAQ can be impacted if the building is not designed correctly. The effect of poor air quality on physical health


is now well established and a growing body of evidence has highlighted the potential impact on mental health, wellbeing, concentration and productivity. However, by choosing the right system and taking a holistic approach to the design of the ventilation, it is possible to achieve both energy efficiency and good IAQ. An important energy efficiency issue for


ventilation is the heat loss that can occur when exchanging indoor air with outdoor air. Effective heat recovery built into the system can help minimise this loss and further improve the efficiency of the HVAC. Units with this capability can take heat from the extracted air and use it to reduce the heating requirements of the building. For


26 March 2022


energy efficiency


Martin Passingham, product manager at Daikin, explains how the correct approach to the design of HVAC systems can balance the drive for energy efficiency with the need for an adequate supply of fresh air to ensure indoor air quality (IAQ)


example, servers can generate a large amount of waste heat that can be usefully used in other areas. With heat recovery, it is possible for the system to frequently achieve a Seasonal Energy Efficiency Rating (SEER) in excess of 6. Further energy savings can be achieved by selecting systems that include technology such as variable refrigerant temperature control. This adjusts the amount of refrigerant flowing through the system and alters the evaporating and condensing temperatures to match demand. This means significantly less energy is needed and overall efficiency is increased. Filtration is also important in ensuring effective and efficient ventilation. All HVAC units will be fitted with filters to keep them free of dust to ensure good operation and to capture and contain pollutants. Choosing indoor units with auto-cleaning filter capabilities ensures that dust can be removed quickly and easily as part of the building’s general cleaning activities. Additionally, the nature and quantity of pollutants in the air and the level of air quality that must be achieved will determine what type of filter is required. General filters will capture larger, heavier


particles, such as dust, while fine filters, which can capture particles the size of bacteria, may be needed where the air must be cleaned to a higher standard. There are also high-efficiency particulate air (HEPA) filters or ultra-low particulate air filters (ULPA) filters for specialist environments, such as clean rooms. Alongside best practice design and specification,


there are further steps that can be taken to improve IAQ. Plasma ionisation technology is a low-maintenance and cost effective ‘fit and forget’ solution for new or existing systems that can help remove harmful particles, VOCs, bacteria and viruses from the air.


The Plasma ionisation unit does not affect


the performance of the ventilation and works by producing a stream of positive and negative oxygen ions. Airborne particles such as smoke, dust, pollen and mould spores are charged by the ions and stick together, increasing their size and allowing them to be captured easily, even by lower grade filters. Bacteria and virus cells bond with the oxygen ions as they divide to reproduce and are destroyed. When the ions come into contact with VOCs it causes a chemical reaction that breaks down their molecular structure. Similarly, odorous gases and aerosols are oxidised and neutralised on contact with the ions. Effective ventilation is essential to deliver a


high IAQ, but it must also be energy efficient to meet the latest requirements and minimise the environmental impact. Taking a whole building approach to the design of the HVAC system and employing the latest innovations and technology can help ensure both goals are met.


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