At the height of the COVID-19 pandemic, ventilation was in the spotlight as never before for schools and other public buildings.
Teachers were asked to increase air flow in classrooms to try and slow the spread of the virus and scientists want that focus to remain. They say the advantages offered by good ventilation also include lower levels of infection for colds and flu, as well as providing an environment which helps children to concentrate and improve their performance in class.
In an article published in the TES last year, Professor Cath Noakes from the School of Civil Engineering at the University of Leeds and Dr Henry Burridge from Imperial College London, said: “It would be remiss to ignore ventilation and its importance in schools – especially if we really are ‘learning to live’ with COVID-19 or looking to boost attendance.
“Ventilation doesn’t just reduce the risk of illness. Studies have shown that it can also improve pupils’ concentration, cognitive performance, and productivity – in addition to reducing a range of respiratory symptoms. Schools with better ventilated classrooms have even been shown to have higher test scores.”
The article added that ventilation in schools could be achieved simply by opening doors and windows when safe to do so but noted that other measures could also be deployed: using fans or devices that clean the air by filtering out viral particles or disinfecting them.
Professor Noakes concluded: “There needs to be long-term focus on ventilation in schools. It should not be something that we look at when there is an outbreak of an infection. Improving the quality of air inside schools is much more than reacting to an outbreak of an infection. It has much wider benefits that reduce absenteeism of staff and students and improves wellbeing and educational performance.”
Types of mechanical heat recovery ventilation units
Many manufacturers offer small residential ventilation units through to large commercial air handling systems. Here we provide an overview of Mechanical Heat Recovery Ventilation (MHRV) suitable for commercial and domestic applications. More than one unit can be installed for larger commercial and even industrial applications where air handling units may not be suited.
MHRV units are designed to extract stale indoor air and bring in fresh, filtered air. The units can be ventilation only or integrated with a DX coil to provide air conditioning. Many can be stand-alone or fully integrated as part of a total HVAC solution.
MHRV units offer ‘free cooling’ and ‘heat recovery’. For example, if the air outside is colder than the inside room temperature, select heat recovery mode (sometimes referred to as heat exchange mode) and the rejected warmer air will exchange its heat energy with the incoming cooler air, raising the clean, fresh incoming air temperature. Or, in the summer months, keep the cooler air coming in without increasing the temperature with the bypass mode.
See diagram below
Some manufacturers use the term total heat exchange. This means that the heat recovered in heat recovery mode is sensible and latent (heat and moisture recovery) and determined by the type of heat exchanger used inside the unit. This filter will need replacing to ensure quality of air.
LG Energy Recovery Ventilation, or ERV, is suitable for domestic and commercial applications. With an incorporated CO2 sensor and air purification system, the ERV unit can be stand-alone or added to an LG VRF system and controlled as one.
Mitsubishi Electric Lossnay ventilation units are ultra-quiet, making them perfect for homes. They have a third filter slot for an optional NOx filter to further improve indoor air quality where required, great for allergy sufferers. Their commercial range includes a reduced-height unit for installation in ceiling voids.
Daikin ventilation units can also be combined with their Sky Air or VRV systems. All units offer heat recovery mode and can recover up to 81% of outgoing heat. Units start as low as 10 m3/h spanning across domestic and large commercial applications.
Midea Heat Recovery Ventilation (HRV) units are also quiet in operation and offer heat exchange, air supply, exhaust and auto modes. Their range is from 200 m3/h to 500 m3/h, suitable for the commercial sector.
Further reading: Benefits of different types of ventilation
We can advise which unit would suit your application and budget best.