HEATING, VENTILATION & AIR CONDITIONING
A BREATH OF FRESH AIR The COVID-19 pandemic has positioned indoor air quality (IAQ) front and centre of
the news agenda, accelerating calls for a systemic approach to delivering fresh air into public spaces. There is, however, a balance between providing sufficiently high IAQ, while maintaining ambient temperature and keeping energy costs to a minimum. David Millward, group product manager at Elta Group, comments
T
he COVID-19 pandemic has resulted in public confidence in buildings being
damaged following the closing down of many public spaces, coupled with an increasing focus on infection transmission via indoor air quality (IAQ). Many urban environments are now having to be reshaped, and with a recent Government whitepaper stressing that ventilation is an important factor in mitigating against the risk of infection transmission, more must be done to improve indoor air quality. However, confusion and misunderstandings
persist over how we define ‘fresh’ air. Emphasis is justifiably being placed on contractors and developers to deliver high quality air to the inside of buildings, but it is important that we establish a reasonable baseline to work towards.
PUBLIC PERCEPTION Most dictionary definitions of ‘fresh air’ state that it is simply air that comes from outside. While this is far too simplistic, it is important for those working within the ventilation industry to understand that this is a prevailing perception among large swathes of the general public. Consider, for example, a multiple-storey
office that opens its windows to allow ‘fresh’ air to circulate into the building. The likelihood is that the air flowing through the window contains a higher volume of
CO2, amongst other pollutants, than the air already inside the building. If we are approaching the subject of IAQ from the perspective of minimising particulates in the atmosphere, then this rudimentary definition of ‘fresh air’ fails building occupants. Even away from more urban locations,
air which might generally be considered ‘fresh’ isn’t necessarily the case according to legal definitions. This is where it is critical that contractors and those tasked with delivering ventilation solutions familiarise themselves with the latest regulations. This will ensure that alongside being able to meet compliance, they can become a trusted source of knowledge on the subject for their customers.
LEGAL DEFINITION Finding a singular legal definition of ‘fresh air’ is challenging, such is the range of
28 ENERGY MANAGEMENT - Autumn 2021
information and factors at play. In many cases, there is an assumption (or at least a reliance) on outdoor air being of reasonable quality. However, as we have already highlighted, the quality of outdoor air is not always sufficient, nor is it immediately controllable. Consultation
Demand-controlled ventilation (DCV) enables air circulation to be adapted to meet a change in occupancy levels or alterations to the internal layout of a room
documents for Parts L and F of the Building Regulations detail a change in emphasis towards air quality, with some specific guidance on monitoring IAQ in offices. There should be the means within
ventilation systems to measure CO2 and other air quality indicators, which helps to ensure that the ‘fresh’ air being brought in from outside is suitably healthy. There will also be specific guidance on how
to ventilate certain types of buildings, or rooms in which particular activities are taking place. For example, in rooms where there is likely to be singing, loud speech, exercise, or large numbers gathering, there should be a provision of a minimum of 15 L/s per person of outdoor air. Whole building ventilation rates should be 10 L/s pp or 1 L/s per m2
, with the means to increase by 50%. Although the definition of ‘fresh air’ is
currently lacking clarity, contractors should still ensure compliance by working towards these minimum ventilation rates. It is also critical to be aware that wider factors such as thermal comfort are considered. One of the issues with increasing flow rates is that it can result in a higher volume of cooler air being brought into the room. There is a delicate balancing act between providing sufficiently high IAQ, while maintaining ambient temperature and keeping energy costs to a minimum.
DEMAND CONTROLLED VENTILATION This is where demand-controlled ventilation (DCV) has a significant role to play. It facilitates the adjustment (whether that’s automatic or manual) of ventilation rates according to what is required. This ensures
that air circulation can be adapted to meet a change in occupancy levels or alterations to the internal layout of a room, thus keeping IAQ sufficiently high but in a precise, targeted, way that won’t incur unnecessarily high energy bills. Perhaps more importantly, DCV is a flexible
approach that can help to increase the lifespan of a system. If regulations tighten and the requirement to deliver even ‘fresher’ air dictates a higher ventilation rate, this is achievable provided the system was originally installed with additional capacity. This enables systems to either increase
or decrease their output depending on the situation, whether that’s working up to meet compliance, or down to minimise energy costs, e.g. in the face of an empty room. This is why the inclusion in the Building Regulations (mentioned above) of the stipulation that systems should have the means to increase their performance by 50% is so crucial.
DEFINING ‘FRESH AIR’ Moving forwards, it is important that the legal definition of ‘fresh air’ becomes more prescriptive, and moves away from a reliance on high-quality outdoor air. This will ensure a more standardised level of what constitutes good IAQ, ultimately raising levels across the board. But, by taking advantage of the latest technology, particular in relation to DCV, it is possible to ensure the ongoing quality of air inside public buildings.
Elta Group
https://eltagroup.com
www.energymanagementmag.co.uk
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