Martin Passingham, Department Manager Product and Training at Daikin, explains how those responsible for public sector buildings can balance the need for energy efficiency with providing a healthy indoor environment by taking a holistic approach to HVAC.
The decarbonisation of buildings is now a key priority as the UK strives to achieve net zero by 2050. However, the higher levels of airtightness required to achieve energy efficiency means that indoor air quality (IAQ) can be affected if it is not approached correctly.
The consequences of poor indoor air quality are increasingly well established. It has been linked to both short- and long-term physical health issues as well as growing evidence that it may impact mental health and influence conditions such as depression and bipolar disorder. In schools, poor IAQ can be detrimental to children’s ability to concentrate and learn while in hospitals it may affect patient recovery.
Indoor air quality is impacted by a wide range of factors, and air pollutants can originate from sources both inside and outside the building. This can make ventilation a challenging issue as there is a need for indoor air to be refreshed but this must be done in a way that does not introduce additional pollutants.
Furthermore, a key energy efficiency issue with regard to ventilation is the heat loss that can occur when exchanging indoor air with outdoor air. Mechanical ventilation systems that include effective and efficient heat recovery can help minimise this loss and improve the efficiency of the HVAC. Where the building has areas with different needs, units with this capability can take the heat extracted from one area and use it to heat another space as well as deliver cooling if required by using the colder incoming air.
Additionally, efficiency can be increased with climate control systems that feature technologies such as variable refrigerant temperature (VRT) control. This adjusts the amount of refrigerant flowing through the system and alters the evaporating and condensing temperatures to match demand, meaning significantly less energy is required.
Ensuring effective filtration of the air is another central element for IAQ and energy efficiency. All HVAC units will be fitted with filters that are designed to keep them free of dust, principally to ensure good operation. However, it is important to ensure that the correct filters are fitted to remove particulate matter (PM) from the supply air. The type of filter required will depend on what is needed to achieve the PM threshold level based on the pollutants present in the exterior air. These threshold levels are derived from the Air Quality Guidelines published by the World Health Organization (WHO).
Regular cleaning of these filters is important but can be time consuming, especially for larger buildings. Choosing indoor units with auto-cleaning filter capabilities ensures that dust can be removed quickly and easily. This prevents contaminants and odours circulating in the room and ensures the unit can operate efficiently. It has the added advantage of making cleaning and maintenance easier as often the collected dust can be removed during the standard building cleaning process, which is especially valuable for busy public buildings.
Additional ways to improve IAQ
Beyond choosing the right system and ensuring the correct design, there are additional steps that can be taken to improve indoor air quality. Low maintenance, cost-effective devices, such as plasma ionisation technology, can be installed in new and existing systems to help remove harmful particles, volatile organic compounds (VOC), bacteria and viruses from the air.
Plasma ionisation, which does not affect the performance of the system, works by producing a stream of positive and negative oxygen ions that react with, and neutralise, the contaminants. Other 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.
With the drive for increased air tightness of buildings, effective and efficient ventilation is increasingly important to ensure that energy efficiency targets are met while providing a healthy and comfortable indoor environment for building users or occupants.
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