A colourless, odourless gas produced by human respiration, combustion processes (e.g., gas boilers, cooking), and organic decomposition.
Definition:
Carbon dioxide (CO₂) is a naturally occurring gas critical to life processes but problematic in elevated indoor concentrations. In the context of UK building regulations (Approved Document F 2022), CO₂ serves as a key indicator of indoor air quality (IAQ). Excessive CO₂ levels signal inadequate ventilation, which can lead to occupant discomfort, reduced cognitive performance, and health risks.
Relevance to UK Building/Retrofit Sectors:
- Ventilation Compliance: Approved Document F mandates minimum ventilation rates in dwellings to limit CO₂ concentrations. For example, whole-dwelling ventilation rates (Table 1.3) ensure CO₂ remains below 1,000 ppm (parts per million), a threshold for acceptable IAQ.
- Retrofit Challenges: Energy-efficient retrofits (e.g., insulation, airtightness improvements) risk trapping CO₂ indoors. Systems like VENTI Fluxo (mechanical ventilation with heat recovery) are designed to address this by supplying fresh air while retaining heat.
- Monitoring: CO₂ sensors are increasingly integrated into smart HVAC systems to dynamically adjust ventilation, balancing energy efficiency and air quality.
Practical Example:
In a retrofit project upgrading a 1930s terraced house, post-insulation CO₂ levels spiked to 1,500 ppm during occupancy. Installing a VENTI Aria continuous mechanical extract system in wet rooms and Fluxo units in habitable rooms reduced CO₂ to 800 ppm, complying with Part F while maintaining energy efficiency.
Key Regulation Reference:
- Approved Document F (2022): Section 1.23–1.25 specifies ventilation rates to mitigate CO₂ build-up, particularly in bedrooms and living areas.