The air exchange rate (AER) refers to the number of times the air within a defined space, such as a room or building, is replaced with fresh air over a specific period, typically measured in hours.
In the UK house building and retrofit sectors, particularly under Part F of the Building Regulations 2010, the AER is critical for ensuring adequate ventilation and maintaining indoor air quality. The regulations set out minimum ventilation requirements to mitigate indoor air pollution and moisture accumulation, which can lead to health issues and structural problems.
Explanation and Real-World Application
The AER is expressed in air changes per hour (ACH). For example, an AER of 2 ACH indicates that the entire volume of air in a room is replaced twice every hour.
Building Regulations Part F specifically outlines these requirements in Requirement F1, which states that “there shall be adequate means of ventilation provided for people in the building.” This includes ensuring that the air exchange rate is sufficient to manage pollutants and moisture effectively.
Practical Example
In a kitchen, where cooking activities generate significant moisture and pollutants, achieving a higher AER is essential. For instance, Table 1.1 in Approved Document F specifies minimum extract ventilation rates for kitchens, recommending an extract rate of 60 litres per second for kitchens without a cooker hood and 30 litres per second for those with an extracting cooker hood.
If a kitchen is designed with an AER of 5 ACH, it ensures that the air is replaced five times an hour, effectively managing humidity and cooking odours. This is crucial for preventing mould growth and maintaining a healthy indoor environment, as excessive moisture can lead to the proliferation of mould, which is addressed in Appendix B of Approved Document F, which outlines performance criteria for moisture control.