What Is an Air Tightness Test? (Blower Door Test Guide)
An air tightness test, often called a blower door test, measures how much uncontrolled air escapes from — or enters — a building through gaps and cracks in the structure. It is an important check in both new builds and major renovations, used to verify energy efficiency, construction quality, and compliance with building regulations.
As modern homes become more insulated and airtight, testing is essential. Without measurement, hidden air leaks can reduce performance, increase energy bills, and undermine the effectiveness of ventilation systems.
How an Air Tightness Test Works
An air tightness test is carried out using specialist equipment that includes a calibrated fan fitted temporarily into an external doorway. The fan changes the air pressure inside the property while sensors record how much air flow is required to maintain a set pressure difference.
The process typically involves:
– Closing all external doors and windows
– Opening internal doors
– Running the calibrated fan to pressurise and depressurise the building
– Measuring air flow and pressure levels
– Calculating the building’s air leakage rate
Engineers may also use smoke tools or thermal imaging to locate specific leakage points around window frames, doors, loft hatches, service penetrations, and ductwork.
Why Air Tightness Testing Matters
Uncontrolled air leakage can lead to multiple problems in a property. Testing helps identify and prevent:
– Excess heat loss and higher energy bills
– Draughts and uneven room temperatures
– Condensation risks inside walls and roofs
– Reduced heating system efficiency
– Poor overall building performance ratings
A tested and properly sealed building is more comfortable, more efficient, and cheaper to run.
Understanding the Test Result
Results are given as an air permeability rate, showing how much air leaks through the building envelope under standard pressure conditions.
In simple terms: Lower score = tighter building = better energy performance.
However, airtightness must always be paired with correctly designed ventilation. A very airtight home without proper ventilation can develop moisture and air quality issues.
Airtightness and Ventilation Go Together
As buildings become tighter, controlled ventilation becomes more important. Systems such as MVHR, MEV, or PIV ensure fresh air supply while removing moisture and pollutants.
At KEPA Solutions, air tightness testing is often combined with ventilation assessment and commissioning, ensuring the building is not only efficient — but also healthy to live in.
Air Tightness Testing with KEPA Solutions
KEPA Solutions provides professional air tightness (blower door) testing, ventilation design, and system commissioning services. We support homeowners, builders, and developers in achieving compliant, energy-efficient, and high-performance buildings.
Contact KEPA Solutions today to book your air tightness test and ventilation check.