One of the consequences of the challenging last 18 months has been a noticeable increase in the attention given to indoor air quality (IAQ). This has been the case throughout the ventilation supply chain, from government and industry bodies, all the way through to facilities managers, contractors, and even consumers. But what do we mean by ‘good IAQ’, and how do we achieve it in our buildings? Alan Macklin, Technical Director at Elta Group, and Chairman of the Fan Manufacturer’s Association explains.
Despite the difficulties of the past year and a half, the renewed focus on the quality of indoor air can be seen as something of a silver lining. It is an important step forwards, and one which we must as an industry maintain momentum if we are to deliver tangible improvements.
In spite of this positive growth in awareness of IAQ, certain obstacles remain which could prevent progress. We need to establish a clear definition of what we mean by ‘fresh air’, moving away from the vagueness that is currently inherent within building regulations. Once this is achieved, there needs to be a greater understanding of the solutions that are available to deliver high-quality air into buildings.
What is good IAQ?
In layman’s terms, good IAQ is often linked with ‘fresh air’. However, this term is problematic, because all-too-often ‘fresh’ is simply understood as ‘outside’. This fails to take into account the issues of outdoor pollution, which can be of particular concern in urban locations.
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’ does not go far enough to adequately protect building occupants.
|Building Regulations hint at a change in emphasis towards air quality, with some specific guidance on monitoring IAQ in offices.|
It is also true that most assessments of IAQ focus solely on CO2 levels, but this is just one of several pollutants that it is important to ventilate out of spaces. It serves as a useful proxy for how high the quality of air is, but sophisticated monitoring will enable a thorough and more nuanced approach.
Finding a singular legal definition of ‘fresh air’ is challenging, such is the range of information and factors at play. Consultation documents for Parts L and F of the Building Regulations hint at a change in emphasis towards air quality, with some specific guidance on monitoring IAQ in offices. For example, 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.
Delivering high-quality air
Although the definition of ‘fresh air’ is currently lacking clarity, contractors should still ensure compliance by working towards 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, for example, is that it can result in a higher volume of cooler air being brought into the room. It highlights the delicate balancing act between providing sufficiently high IAQ while maintaining ambient temperature and keeping energy costs to a minimum.
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.
With demand control, a value is set at an initial required duty, but because it is speed controlled and monitored, the airflow can be adjusted automatically depending on condition, adjusting airflow and energy use. Specification typically allows for 20% more airflow and 10% more pressure than the selected ventilation rates, however, this is predominantly to cover miscalculations in system design, and often removed during the tender process to lower equipment cost. We have to move away from this approach, and including this increase above the minimum design requirement will provide assurance if the needs of the building change.
Systems designed for future legislation
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. Although the definition of ‘fresh air’ is currently lacking clarity, contractors should still ensure compliance by working towards minimum ventilation rates.
Take energy legislation for example, which controls most elements of the modern-day built environment. With legislative limitations placed on the amount of electricity a ventilation system can consume while operating, a common mistake made when selecting fans is to ignore the additional energy losses – surplus to specific fan power (SFP) – associated with speed controls. These can be significant and should be added to the power consumed by the fan to accurately calculate a ventilation system’s SFP.
DCV 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 becomes even more crucial with the inclusion in the draft revision of the Building Regulations, which stipulates that systems should have the means to increase their performance by 50%.
The current climate serves as a watershed moment for indoor air quality and, as an industry, we have to seize the opportunity. As public spaces start to reopen, there is a genuine and urgent need to prioritise IAQ as a fundamental indicator of building health and safety. Establishing a clear definition of how we define good air quality, and then installing systems that are suitable both now and into the future, will go a long way to determining our success.