Energy usage is often prioritised over indoor air quality, despite the potential benefits to wellbeing and learning. Alan Macklin and Ana Cross at Elta Group discuss how schools need to place both front of mind and implement quality-designed mechanical ventilation…  

The pandemic has certainly increased awareness around indoor air quality, with the high levels of CO2 across building stock becoming a growing concern. Despite this, reducing energy usage in line with sustainability aims continues to take precedence. 

Natural ventilation methods such as opening windows have often been used by schools in an attempt to address both matters. But what must be realised is that simply letting in outside air does not equate to good indoor air quality. Heavily urbanised or suburban areas tend to be the surroundings for many schools, where a high count of nitrogen oxide is in the air. Equally concerning is the presence of harmful particles such as car brake pad dust, fumes and sulphur dioxide.

For younger, more vulnerable individuals such as pupils, air pollutants can be particularly harmful to their wellbeing. Building on this, numerous scientific studies have demonstrated that CO2 and harmful particulates also directly hinder learning and concentration levels. 

With the school rebuilding programme now set in motion, it is undoubtedly time for learning environments to be improved through better ventilation strategies that take indoor air quality into account. 

Understanding and managing air quality 

It is important that there is better understanding around what good quality or ‘fresh’ air is to ensure best practice in ventilation. As mentioned, air brought in from outside isn’t necessarily good quality air. Harmful compounds can be present that impact both general health and concentration levels in pupils. 

The misconceptions around ventilation don’t end here. The rising popularity of air purifiers points to a false impression that continuous recirculation and purification constitutes fresh air. Relying solely on air purifiers allows CO2 and VOC (volatile organic compound) levels to increase and subsequently be inhaled as the air becomes stale. A good quality ventilation system must be a comprehensive solution that both manages CO2 levels and extracts pollutants before air reaches the classroom. 

There is clearly a need for better guidance around air quality management, and upcoming changes to legislation reflect this sentiment. While the Building Bulletin (BB 101) is in place as a framework for ensuring effective ventilation, updates to Part F of Building Regulations will introduce firmer guidelines. Among these amendments, buildings will be required to provide sufficient ventilation to keep CO2 levels below 800ppm (parts per million). 

With the emphasis being on greater understanding and adherence, these conditions will be key to schools introducing appropriate ventilation solutions. 

Demand-controlled ventilation

The CO2 level rises as a result of building occupants exhaling, while increasing the ventilation rate reduces it. As such, CO2 should be considered as a proxy for air quality. Measuring CO2 can allow for a ventilation system to control both air quality and energy usage effectively. 

It is common for building ventilation systems to operate at constant or pre-determined rates that are specified to maximum occupancy levels. This results in energy wastage from not just the functioning fan, but also from the air conditioning in both heating and cooling modes. 

MVHR (Mechanical Ventilation with Heat Recovery) solutions, such as Elta Fans’ PREMA range, differ in their ability to control the amount of airflow to suit occupancy levels through demand-controlled ventilation (DCV). DCV opens the door to cost-effective ventilation while also maximising indoor air quality. 

Closed loop speed control for both EC and AC motor options provides major energy savings as the fan power is proportional to the speed cubed. Ambient conditions in the space are continuously measured and monitored through CO2 or temperature sensors to provide real time feedback to the zone controller. Fan speed can then be adjusted and the ventilation rate modulated to match building use and occupancy level. It’s these technical aspects of DCV that enable significant energy savings. 

Elements of design

The design properties of the ventilation system should be taken into account before a decision is made. This is an area where long term energy gains and subsequent cost savings can also be achieved. 

PREMA’s units for instance have a have a free running, backward curved impeller and special three-dimensional blade geometry as part of the design. The application therefore benefits from reduced rotational tone which enables higher performance and greater energy savings. 

Another aspect to take into account is the capacity for thermal energy recuperation. The large surface area of the heart exchanger in PREMA’s units enhances thermal energy exchange to allow as much as 92% of thermal energy to be recovered. 

Supporting best practice

During design and specification of a mechanical ventilation system, it is vital to consult the manufacturers in order to achieve desired performance. Here, industry professionals can offer best practice and guidance. 

For schools in particular, there should be close attention paid to the specification of high-quality filtration methods for restricting external pollutants. With this in mind, all ventilation systems from Elta Fans come with ePM1 Filters that offer high filtration levels and follows the ISO 16890 Standard. 

Another key consideration when specifying is power output from the fan. This must be sufficient to overcome any pressure development drop due to the filtration solution. Further deliberation will be needed for the layout and length of ducting, as well as any other auxiliary components in the design. 

Any solution must be well maintained and serviced to ensure efficient operation throughout its lifecycle. Consulting a manufacturer here can ensure an appropriate maintenance schedule is put in place. 

The future of school ventilation 

Ventilation and air quality evidently need to be front of mind as the school rebuilding programme comes in effect. Learning environments must have a well-engineered system for ventilation and the right level of support to implement the appropriate solution. From manufacturers through to specifiers, professionals across the industry will need to consider how to deliver good indoor air quality and improve future learning environments. 

To find out more about Elta Fans’ range of ventilation solutions, visit: https://www.eltafans.com/