In this blog, we’ll consider some key factors to provide great ventilation for school buildings and good air quality for pupils.
In our last blog, we talked about the science of breathing and the key facts that emphasise the importance of modern buildings providing adequate ventilation to support our physiological needs.
What is the current state of ventilation in school buildings?
Broadly speaking, research has indicated that in existing schools
- Average CO2 levels can often reach well in excess of 2000 ppm, and have frequently been reported as high as 6000 ppm in various studies.
- High levels of CO2 have had a recognisable impact on cognitive function, health, learning and exam grades.
- There is a need for a greater appreciation of ventilation in school (and office) environments to support occupant health and productivity
When we think about effective ventilation for our school buildings, we must consider not only new building designs, but also the needs of existing ones. With over 30,000 schools in the UK, addressing existing building stock and classroom conditions is both a massive challenge, but also a great opportunity to provide better environments for the 10 Million UK students currently spending most of their days learning in them.
Ventilation Approaches
The two main methods of ventilating buildings are Natural Ventilation (for example using opening windows) or Mechanical Ventilation, as well as the potential to have a mix of both where budgets allow.
There are pro’s and con’s of both;
Natural Ventilation
Natural ventilation is generally accepted as using less energy to deliver the fresh air using wind pressure and natural buoyancy through partially opened vents, but these vents need controlling and may sacrifice some heat losses in winter. When delivered effectively, naturally ventilated spaces are generally better perceived and enjoyed by occupants compared with mechanical ventilation – providing that external surrounding conditions are adequate.
Employing Natural Ventilation may sometimes be limited by outdoor pollutants or extreme weather conditions. Key considerations like avoiding draughts and dealing with temperature extremes must be properly considered and mitigated through good design and control practices.
Manual control of windows may not always offer a dependable way of achieving and maintaining real world air quality (and energy balance) using Natural Ventilation – so automation may be considered.
Good design practices and innovative approaches to Natural Ventilation control may offer the best solutions for Scottish buildings.
Mechanical Ventilation
Mechanical ventilation is often considered easier to control and may have an element of heat recovery although often in densely occupied spaces the benefit of this can only be appreciated at winter temperature extremes.
The mechanical approach has the potential to offer cooling and filtration for extreme summer conditions or pollution if outdoor conditions dictate, but this comes at a capital, running and environmental cost.
Mech vent may be noisier, more expensive to install and run, and requires regular maintenance and proper control to avoid some common health issues associated with mechanically ventilated buildings. Fans, compressors and filters all have an energy penalty too, compared with Natural Ventilation.
Natural ventilation is broadly encouraged IF where good air quality, comfort levels and real world performance can be achieved.
So how does that stack up in Scotland?
Natural ventilation is broadly encouraged IF where good air quality, comfort levels and real world performance can be achieved.
How does that stack up in Scotland?
Air Quality – Lets talk about pollution
Natural ventilation holds great potential to offer good air quality and great energy savings much of the time, but pollution should rightfully be a consideration as part of ventilation decision making;
A survey by the charity Global Action Plan found that out of 28,965 schools in the UK, 7,852 are in areas where pollution levels are above recommended limits. Clearly in some areas, pollution may limit the safe use of Natural Ventilation..however, it’s clear the vast majority of those schools (over 70% in the UK) are in areas where pollution is below recommended limits, and therefore Natural Ventilation may offer an effective and energy efficient option if properly employed.
What’s more, 98% of all of those schools are in England, so how does air pollution stack up for schools in Scotland, and could optimised use of Natural Ventilation be the answer?
Scotland enjoys a high level of air quality, and over the past three decades levels of the main air pollutants have declined significantly. Between 2005 and 2020 (the latest year for which figures are available), nitrogen oxide emissions have decreased by 61%, fine particulate matter by 52% and sulphur dioxide by 92%.
Scottish government have also laid out a clear commitment to improving air quality in Scotland – so the future looks bright for good outdoor air quality and in turn the opportunity to harness that to provide great indoor spaces.
What about local climatic challenges? Feeling hot hot not?
The most common concerns for Natural Ventilation are whether extreme summer temperatures create too greater burden on Natural Ventilation to maintain comfortable indoor spaces, and whether extreme winter conditions dictate the need for heat recovery or mechanical approaches.
Summertime overheating? Thankfully in Scotland, peak temperatures are around 4 degrees lower on average than in England, with average peaks at around 17 deg C, meaning overheating can often be very well mitigated with Natural Ventilation without the need for mechanical cooling. What’s more, lower night-time temperatures in Scottish summers unlock the potential for night cooling even if summer daytime temperatures do begin to increase. So it seems we are blessed in Scotland with a climate ideal for considering natural means of ventilation.
Only owners, designers and engineers can fully assess the benefits and specific requirements of each building – but generally speaking – Scotland offers good air quality and climate close to the sweet spot for embracing the many benefits of Natural Ventilation, most of the time…
How can we best make Natural Ventilation work for our schools in Scotland?
Follow us and we’ll keep you posted on our next blog – key considerations for Natural Ventilation in Scottish Schools – for comfort, air quality and energy performance!
