www.heatingandventilating.net
By Ability Projects global product manager – H&V systems, Jon Freeman
Why choose high-grade filtration?
Increasing ventilation flow and filtration rates for better Indoor Air Quality (IAQ)
The impact of COVID-19 on the architecture of future ventilation systems is still uncertain, however, we can take steps to improve occupant wellbeing in buildings. Improving a commercial building’s ventilation strategy, with the aim to increase Indoor Air Quality (IAQ), has been a talking point in the industry for some time. With the COVID-19 pandemic raising the wider focus on IAQ, this awareness has increased and accelerated the need for viable solutions. Improved IAQ is especially important for offices, where businesses and organisations want to transition back to the workplace in as safe a way as possible, to instil confidence in a workforce that has been working from home for over a year.
It is an accepted view, supported by the World Health Organisation (WHO), that increasing ventilation and filtration rates significantly improve IAQ, and can also help to mitigate the risk of spread of COVID-19 whilst also providing a healthier indoor environment. Whilst the key topic of conversation relating to occupant safety currently centres around increased ventilation rates, whether through mechanical or natural means, it is also important to consider how the increased volume of fresh air is circulated throughout the occupied space.
Fan coil units (FCUs) are, by themselves, a recirculatory product, drawing air from a particular space, and providing heating or cooling dependant on user demand. They are also frequently used as the means to distribute fresh air from the central supply system. Their installation and associated delivery ductwork systems are carefully designed to ensure all areas of the occupied space are supplied with conditioned air, and are recognised within the CIBSE COVID-19 Ventilation Guidance “If there is a good outside air ventilation supply (either mechanical or natural) to the room or zone then the action of the fan coil unit fan will help de-stratify the air and reduce the chance of pockets of stagnant air, helping to dilute any airborne pathogens.”
FCUs are already widely installed in commercial spaces and specification in the residential sector is growing. So, how can we use this technology to improve IAQ further?
Which available solutions may help improve IAQ in preparation for the transition back to offices? There are currently three main solutions available on the market that can be applied to FCUs to improve IAQ in commercial spaces.
Bipolar Ionisation accessories have been recently launched on the market and are available for specific ventilation systems. The technology aims to actively remove pollutants in a particular space. Laboratory tests by the manufacturers, conducted in smaller spaces, confirm the efficacy of the system in the limited test environment only.
Until peer reviewed studies and an established testing structure validate an improvement from the application of bipolar ionisation, any claimed benefits in IAQ cannot be substantiated. Although this may change as the technology advances, its benefit and long-term impact in a real-world fan coil application are yet to be proven.
Ultraviolet Germicidal Irradiation (UVGI) uses shortwave ultraviolet (UV-C) light to inactivate microorganisms, and has seen successful application, particularly in the healthcare sector, for many years. There is no doubt about the effectiveness of UV-C at inactivating viruses, bacteria and fungi, and this has been proven through recognised test methodologies. The technology is applicable in some settings but has its challenges for implementation. The duration of exposure and UV light intensity are two components that maximise the effectiveness of UV-C. This makes the technology design specific as the individual flow rates of an FCU system complicates its application. An additional consideration is direct exposure to UV-C light must be avoided, making retrofit applications challenging. Specific designs may be required to integrate the technology within existing FCUs.
Mechanical air filters are widely used in HVAC systems, and are classified by their effectiveness at removing particulate matter. They serve many different purposes; from coarse filters used for protecting equipment to ultra-fine filters, which can clean the incoming air stream to a standard suitable for operating theatres. Higher-grade filters are typically seen within supply air systems to ensure outdoor air contaminants are removed prior to circulation though the occupied space.
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How do these methods compare in the context of fan coil unit application at this moment in time? Technology such as bipolar ionisation and UVGI may play a role in future ventilation systems that seek to specifically combat airborne viruses, but more needs to be done to prove the benefits and to ensure safe and commercially viable application in combination with the wider HVAC system. High grade mechanical filtration is an established technology with proven and tested credentials, which is currently installed in the majority of fresh air supply units. Given the recirculatory nature of fan coils, along with the fact any fresh air being passed though the unit has already been filtered, localised protection has typically been restricted to the minimum grade required to protect the long term efficiency and service life of the product. To replace the standard coarse grade filter with finer grade media meant higher internal resistances, reducing product efficiency, whilst increasing both noise and running costs. Each manufacturer has their own recommendations, but even the higher end filtration (G3 in old money) currently in standard use would be classified as ISO Coarse, meaning that less than 50% of PM10 particles are arrested. High grade filtration, which must prevent a minimum of 50% of PM1 particles (F7+ when compared to the old standard), would previously have increased operating pressures to a level unachievable in a standard system. High grade filtration is particularly relevant where building owners are increasingly being recommended to raise ventilation rates. The increase can’t always be achieved mechanically, through existing systems. Natural ventilation might be required, causing an inevitable drop in IAQ. Higher grade filters within FCUs could help to restore the IAQ by continuously filtering all air within the space.
Ability Projects, part of Glen Dimplex Heating & Ventilation (GDHV), have a new high grade filter module available, suitable for new products and for addition to many existing systems. By careful selection of filter media, the resistance in the FCU unit is kept to a minimum, but still provides the benefits of ePM1 60% filtration.
High grade filtration is a technology that is already widely implemented with proven benefits and assurances that there are no negative long- term effects to end users. It is also a cost-effective option. A large number of installed fan coils can be upgraded to high grade filters. In comparison with Bi-Polar ionisation and UVGI, the bolt-on installation is relatively simple and doesn’t require intrusive changes to the existing product.
Have you been considering what options are available for IAQ improvement? For more information on the topics above, or on fan coil units, visit www.
abilityprojects.com/epm1-60 or call 01202 305 800.
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