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FEATURE FOCUS: SCHOOL MAINTENANCE & DESIGN
levels in pupils. Evidenced by the rising popularity of air
purifiers, another misconception is that continuous recirculation and purification constitutes fresh air. In actual fact, this air becomes stale, allowing for CO2 and VOC (volatile organic compound) levels to increase and subsequently be inhaled. While air purifiers do have their place in a ventilation system, they should not be treated as a comprehensive solution. Such applications will remove pollutants, but have no impact on CO2 levels. As such, a good quality ventilation system is one that extracts all pollutants, brings air in from the outside and filtrates it before reaching the classroom.
occupancy levels, resulting in consequent energy wastage. This is not only due to the fan operation, but also includes the energy used to condition the air for both heating and cooling modes. Through MVHR (Mechanical Ventilation with
Heat Recovery) solutions such as Elta Fans’ PREMA range, the amount of airflow can instead be controlled to suit occupancy levels and delivered through demand-controlled ventilation (DCV). DCV is recognised as a reliable method of ensuring a building is ventilated cost effectively, while 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. CO2 or temperature sensors are used to continuously measure and monitor ambient conditions in the conditioned space and provide real time feed back to the zone controller. From here, fan speed is adjusted – modulating the ventilation rate to match the specific use and occupancy of the building. Significant energy savings are made by effective DCV, which ensures that the ventilation rate continuously matches the current occupancy rate and varying ambient conditions.
Mechanical means To ensure adequate ventilation, CO2 should be considered as a proxy for air quality. The CO2 level rises as a result of building occupants exhaling, while increasing the ventilation rate reduces it. On this basis, measuring CO2 can allow for effective control of both air quality and energy usage. Building ventilation systems often operate at
constant or pre-determined ventilation rates regardless of the occupancy level of the building. Ventilation rates are normally based on maximum
Efficient energy conversion and recovery With all ventilation solutions, it’s important to consider the design properties of the ventilation system itself prior to making a decision. This is where small yet significant long term energy gains, and subsequently cost savings, can be made. As an example, PREMA’s units have a free
running, backward curved impeller and special three-dimensional blade geometry that provides reduced rotational tone, which provides greater energy savings through higher performance. Attention should also be paid to how much
thermal energy can be recuperated. With PREMA’s units, the thermal energy exchange is
enhanced by the large surface area of the heat exchanger resulting in as much as 92% of thermal energy being recovered.
System support When designing and specifying a mechanical ventilation system, it’s important to always consult with the manufacturers as quite often they can offer best practice and guidance to achieve the desired performance. For schools, there should be a particular focus
on specifying high-quality filtration methods to restrict external pollutants. In line with requirements, all ventilation systems from Elta Fans come with ePM1 Filters that offer high filtration levels and follows the ISO 16890 Standard. When specifying mechanical ventilation
systems, it must be ensured that the fan has enough power output to overcome any pressure development drop due to the filtration solution. Layout and length of the ducting, as well as any other ancillaries involved in the design will also need to be considered. Post-installation, any solution must also be well
maintained and serviced to ensure they are operating efficiently. Here, consulting with a manufacturer can ensure the right maintenance schedule is created and followed.
The future learning environment As the school rebuilding programme comes into effect, it’s clear that ventilation and air quality must not be left behind as an afterthought. Schools must have a well-engineered system for ventilation – whether it is mechanical or hybrid – and receive the necessary support to realise such solutions. From manufacturers to designers, consultants to specifiers and beyond, the entire supply chain must consider how to deliver good indoor air quality and follow through to enable better learning environments for years to come.
June 2022
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