Airtightness testing, also known as blower door testing, is pivotal in whole-building life cycle assessments, significantly influencing energy efficiency and operational emissions by minimising air leakage and reducing the need for heating and cooling. This testing is essential for Whole Life Carbon Assessments, as it mitigates operational carbon emissions by curbing energy consumption across a building’s lifespan. Furthermore, airtightness enhances indoor air quality and the durability of buildings by controlling moisture levels, thereby preventing mould growth and structural degradation. As airtightness compliance becomes more widespread, it aids in standardising building performance, all while providing valuable data to benchmark and enhance the sustainability of both new and existing structures.