What is an Air Test?
Air tightness testing, also known as air pressure or air leakage testing, measures how much uncontrolled air enters or exits a building. This assessment identifies and quantifies air leakage paths—cracks and openings in the building's structure. In essence, air tightness testing provides real-world data for SAP calculations, ensuring new builds are designed and built for energy efficiency, lower bills, reduced emissions, and regulatory compliance.
How Air Testing is carried out
During an air test, a fan is installed in an external door to pressurise or depressurise the building. This creates a difference in air pressure, allowing the tester to measure how much air leaks through gaps, cracks, or poorly sealed areas. The results, typically expressed as the air permeability rate (measured in cubic meters per hour per square meter of building envelope), provide valuable data on the building’s energy performance. Lower air leakage indicates better insulation and energy efficiency, while higher leakage suggests areas that need improvement to reduce energy consumption. The test is carried out once the building is fully enclosed but before final finishes, ensuring a clear understanding of its energy efficiency and helping identify areas for improvement in the EPC rating.
Benefits of Air Testing
In the UK, air permeability testing is a mandatory requirement under Part L of the Building Regulations for most new builds. Failing to meet the minimum air leakage standards can result in costly delays, rework, or non-compliance issues. Beyond regulatory compliance, air tightness testing also improves indoor air quality by reducing the infiltration of pollutants, allergens, and moisture, contributing to a healthier living environment.
Air tightness testing is a critical part of the construction process for any new build, directly impacting energy efficiency, building performance, and compliance with UK Building Regulations. As new homes and commercial properties are designed to meet higher energy standards, uncontrolled air leakage can lead to significant energy loss, making heating and cooling systems work harder and increasing utility bills. Air tightness testing identifies these leaks early, allowing builders to seal gaps and ensure the building performs as designed.
It also enhances occupant comfort by eliminating cold drafts and maintaining consistent indoor temperatures, while helping to prevent condensation, mould growth, and long-term damage to building materials. Additionally, a well-sealed building improves acoustic performance by minimising external noise penetration.
​Air Test Results in SAP
Air tightness test results play a crucial role in SAP calculations, as the measured air permeability rate is a key input for the software. A more airtight building minimizes heat loss, reducing energy demand and improving overall efficiency within the SAP model. Strong air tightness performance contributes to a lower Dwelling Emission Rate (DER) and better Fabric Energy Efficiency, helping meet compliance requirements and achieve higher EPC ratings. While initial SAP assessments use an assumed air tightness value, the final test confirms the building’s actual “as-built” performance. If the measured results differ from the initial assumption, the SAP assessment may need to be revised, potentially affecting compliance outcomes and EPC scores.
Commercial Air Tightness Testing
Commercial air tightness testing is required by Part L of the UK Building Regulations to ensure energy efficiency and reduce carbon emissions in new commercial builds. Beyond compliance, it offers benefits like lower operational costs due to efficient HVAC systems, improved indoor comfort by eliminating drafts, enhanced acoustic performance by reducing external noise, and better indoor air quality by preventing pollutant entry. Ultimately, it's vital for creating high-performing, energy-efficient, and sustainable commercial properties.
To book an air test, simply send us your property drawings and location details — you can upload these through our Get a Quote page or get in touch directly with our office team for assistance.