There is an old adage “build tight, ventilate right”. We are certainly learning to do the former but my experience is that we haven’t got the latter bit sorted. In recent years, there has been a growing awareness of indoor air quality (IAQ) and its impact on human health and well-being. Among the crucial factors affecting IAQ, carbon dioxide (CO2) levels have gained significant attention. CO2, primarily emitted through human respiration and combustion processes, serves as an indicator of indoor air freshness and ventilation effectiveness.
In the next part of our industry insight series Tony Croke, Product Manager for Indoor Climate Solutions in Wavin UK & Ireland, delves into the necessity of ventilation in homes, emphasizing the importance of monitoring CO2 levels to ensure optimal indoor air quality.
The Importance of Ventilation:
Ventilation plays a pivotal role in maintaining a healthy indoor environment by diluting pollutants, regulating humidity levels, and preventing the buildup of harmful gases. Inadequate ventilation can lead to a plethora of health issues, including respiratory problems, allergies, headaches, and fatigue. Moreover, poor ventilation exacerbates the concentration of indoor pollutants, such as volatile organic compounds (VOCs), formaldehyde, and particulate matter, further compromising indoor air quality.
Understanding CO2 Levels:
Carbon dioxide is a colourless, odourless gas naturally present in the atmosphere. While it is not inherently toxic at typical concentrations, elevated CO2 levels indoors can indicate insufficient ventilation and poor air exchange. Human activities, such as breathing, cooking, and heating, contribute to indoor CO2 accumulation. Prolonged exposure to elevated CO2 concentrations can lead to symptoms like drowsiness, poor concentration, and decreased cognitive function, commonly known as "sick building syndrome."
Monitoring CO2 Levels in Homes:
Monitoring CO2 levels is essential for assessing indoor air quality and ensuring adequate ventilation. Portable CO2 monitors, equipped with sensors, provide real-time measurements of CO2 concentrations in indoor environments. 2 people sleeping in a naturally ventilated bedroom with the door shut can easily exceed 1400ppm. The recommended indoor CO2 concentration in Europe is 1000 parts per million (ppm) above outdoor levels, which typically range from 350 to 450 ppm. Exceeding this threshold indicates poor ventilation and will cause feeling of unwellness and necessitates immediate action to improve indoor air quality. Many practitioners in the UK use a measure of carbon dioxide (CO2) concentration in a building as a proxy for IAQ. Various national bodies such as the Department for Education have set standards for CO2 levels in buildings in its own right – in this case stipulating a maximum average value of CO2 of 1500ppm (DfE 2012). In the UK the current Part F of the Building Regulations implies that indoor air concentrations of CO2 should not exceed ~1200ppm.
Strategies for Ventilation Improvement:
Implementing effective ventilation strategies is imperative for maintaining optimal indoor air quality and mitigating the risks associated with elevated CO2 levels. Simple measures like opening windows and doors to facilitate natural ventilation can significantly enhance air exchange rates. Additionally, mechanical ventilation systems, including exhaust fans, and whole-house MVHR ventilation systems, offer controlled airflow and pollutant removal, ensuring a constant supply of fresh outdoor air.
There are multiple practical issues which conspire to affect the effectiveness of ventilation. Actual occupancy rates don’t always equate to design conditions. Flow rates associated with mechanical and passive ventilation systems in practice don’t always equate to design. There are many reasons for this including:
Design. Impractical designs and / or designers “gaming” with calculations so as to demonstrate that standards are met.
Construction / Installation. Ductwork can be prone to damage (particularly, flexible systems), and the practical installation of ductwork, fans, and terminal units does not always equate to what was designed. BSRIA has come across instances of mechanical ventilation systems simply not being connected up to a power supply. Some buildings have a lower air leakage rate than the design.
Commissioning. Poor commissioning, such as ventilation dampers, sensors and controls, can significantly affect performance. The current approved method of measuring air flow from low pressure ventilation systems is also fundamentally flawed, so in practice we don’t really know what the true situation is in many buildings even when these systems are ‘properly’ commissioned.
Maintenance. Poor maintenance of filters and sensors can have a significant impact on flow rates and the effectiveness of filtration. Design issues sometimes make the cleaning of filters or their replacement, or the cleaning of ductwork, somewhat problematic.
Operation. Occupant effects such as not using the ventilation system as per the design intent; manual tampering of controls, sensors, dampers etc. Where mechanical ventilation works with trickle ventilators, they may be shut.
Conclusion:
In conclusion, adequate ventilation is paramount for safeguarding indoor air quality and promoting occupant health and comfort in residential settings. Monitoring CO2 levels serves as a vital indicator of ventilation adequacy, enabling homeowners to take proactive measures to enhance indoor air quality. By adopting effective ventilation strategies and leveraging technological advancements in IAQ monitoring to integrate CO2 monitoring into the ventilation system, we can create healthier, more liveable indoor environments for the well-being of all occupants.
