Increasing Carbon Dioxide (CO2) concentrations are having a major impact on our indoor and outdoor environments. To reduce carbon emissions, buildings have been made more energy efficient.
One example of this is increased airtightness. However, airtight rooms with insufficient ventilation may suffer from poor air quality and high CO2 concentrations.
So, we find ourselves between an iceberg and a hard place; we need buildings to become more energy efficient, but we also need these buildings to breathe. It is important to understand why we should be concerned with the effects of high CO2 concentrations before developing solutions.
At first glance, the impact of CO2 can be deceptive. CO2 makes up about 0.04% of the composition of outdoor air.
For indoor air, current school guidelines (BB101: Ventilation, thermal comfort and indoor air quality 2018) allow the daily average CO2 concentration to rise to 0.1% of the composition of indoor air.
For context, the average outdoor CO2 concentration is said to be about 0.04% of the composition of air. So, why then are we so concerned with room CO2 concentration when it makes up so little of our indoor air?
Increased CO2 concentration have a huge impact on the brain, particularly affecting our cognitive abilities.
In 1904 Danish physiologist, Christian Bohr, found increasing CO2 concentrations in the blood increased blood acidity level, reducing the quantity of oxygen it could carry. This results in the brain receiving less oxygen, reducing cognitive function. This was named the Bohr Effect.
In 2016, Harvard University investigated the link between CO2 concentration and cognitive function. The study sought to find out how varying indoor CO2 concentrations affect cognitive performance in an office environment.
The results were stark: in all categories the performance of the groups was noticeably inhibited by increased room CO2 concentrations. Categories included basic, applied, and focused activity level, information usage, and strategy, all important for cognition.
The effect is much more pronounced between 1,400 ppm and 900 ppm, suggesting a limit as to how much CO2 the brain can handle. When considering these results, one should bear in mind that the Bohr Effect would be amplified on younger occupants.
The impact of high CO2 concentrations could be considered more severe in an exam scenario: 100 to 200 pupils in a large room with poor ventilation for up to three hours at a time.
During that period, without sufficient ventilation the room CO2 concentration could easily exceed 2,000 ppm. If CO2 concentrations are properly managed, exam performance could be improved.
This underpins how management of indoor air quality (IAQ) is critical if we are to succeed in improving our indoor learning environments.
BB101 requires mechanical ventilated classrooms to meet a daily average CO2 concentration of 1,000 ppm. European countries such as Finland, Norway, and Germany permit a maximum CO2 concentration in classrooms of 1,000 ppm.
Penalties may be given for exceeding these limits. Based on the evidence and the experience of our European counterparts, we believe that the key performance indicator (KPI) for classrooms should be that they achieve a CO2 concentration of no more than 1,000 ppm at any time.
In a typical UK classroom, the volume of room air may need to be changed approximately five times per hour to achieve a daily average of less than 1,000 ppm of CO2.
This air will come from outside, but the air outside is heavily polluted. Until we exclusively use “clean” energy sources, this problem will exist.
While some pollutants are not considered damaging, many of them are known to have a long-term impact on health. Poor air quality remains the largest environmental health risk in the UK and is said to be responsible for 4.2 million deaths per year.
Children are among the most vulnerable to pollution’s harmful effects as their lungs are still developing, and arguably the least responsible. As such its vital we take steps to create better learning environments, free of high CO2 concentrations.
Fortunately, we do have methods to mitigate this issue. A mechanical ventilation solution with heat recovery (MVHR) is an optimal choice in both reducing energy wastage and managing CO2 concentrations.
MVHR can recover up to 90% of the energy in the room. The heat is recovered by an air-to-air heat exchanger, using it to warm up the cooler air from outside before it enters the room.
The result is a much lower heating demand for the classrooms and lower carbon footprint. In addition, the room will be well-ventilated with a much lower level of pollution than found outside.
To improve the standards of indoor air quality, better methods of ventilation must be used. Classrooms need fresh, filtered air and a CO2 concentration of less than 1,000 ppm. We encourage you to take this into your own hands and question the air quality in your classrooms.