Air leakage refers to the unintentional flow of air through gaps and cracks in a building’s envelope, particularly around window frames, doors, and seals. The A-Value quantifies this leakage, indicating the volume of air that can pass through these openings under specific pressure conditions, usually measured in cubic metres per hour per square metre of building area (m³/h/m²).
In the context of energy efficiency, a lower A-Value signifies better airtightness, which is crucial for minimising drafts and heat loss. Effective air sealing not only enhances comfort by maintaining consistent indoor temperatures but also contributes to reduced energy consumption, thereby lowering utility bills.
Consider a newly built residential property in the UK designed to meet stringent energy performance standards. During the construction phase, builders implement various sealing techniques, such as using high-quality caulking around window frames and doors, to achieve an A-Value of less than 5 m³/h/m². This level of airtightness significantly reduces the amount of cold air entering the home, resulting in a comfortable living environment and decreased reliance on heating systems.
In retrofit projects, such as upgrading older homes to improve energy efficiency, contractors often conduct air leakage tests (e.g., blower door tests) to identify areas needing enhancement. For instance, an older terraced house might initially exhibit an A-Value of 15 m³/h/m². After applying advanced sealing methods and insulation improvements, the A-Value can be reduced to 3 m³/h/m², demonstrating a substantial improvement in energy performance and occupant comfort.