Level 3 in Air Permeability (Air Leakage) Testing of Existing Dwellings using the Low-Pressure Method

Air Pressure Testing in Existing Dwellings

What is Air Pressure Testing?

Air Pressure Testing, also known as air permeability testing, airtightness testing, or air leakage testing, is a method used to measure the amount of air that escapes from a building unintentionally through gaps and air leakage paths, such as under skirting boards or behind bath panels. This testing method excludes any air leakage through controlled ventilation systems like extract fans.

Introduced in 2002, this method is integral to building regulations for both residential and commercial buildings, which establish maximum limits for air leakage for each building type. Air pressure testing is also incorporated into retrofit processes, now included in PAS 2035/2030: 2023 methodology.

The unintended loss of air from a building can result in higher energy bills for occupants and increased carbon emissions from the building. Due to the convection cycle, when warm air escapes from a building, it is replaced by cooler external air, which then needs to be heated to maintain the building's temperature. The air pressure testing method quantifies this air loss into an "Air Permeability Score." A higher air permeability score indicates greater unintentional air loss from the building.

1. Air Permeability Testing:

   • Air permeability testing, also known as air tightness testing or air leakage testing, measures the amount of air that escapes from a building unintentionally through gaps and air leakage paths in the building envelope.
   • The primary focus of air permeability testing is to assess the overall airtightness of the building envelope and to identify areas where air leakage occurs.
   • This testing method helps determine the energy efficiency of a building by quantifying the amount of heat loss due to air leakage, which can impact occupants' energy bills and carbon emissions.
   • Air permeability testing typically involves pressurising or depressurising the building and measuring the air flow rate to determine the level of air tightness.

1. Background Ventilation Testing:

   • Background ventilation testing, on the other hand, assesses the effectiveness of the building's background or continuous ventilation systems in providing fresh air to the occupants.
   • Background ventilation systems are designed to provide a steady flow of fresh air into the building while removing stale air, without relying on windows or doors being opened.
   • The focus of background ventilation testing is to ensure that the ventilation system is functioning properly and meeting the required airflow rates to maintain indoor air quality and occupant comfort.
   • This testing method may involve measuring airflow rates, checking ventilation system components such as air vents and ductwork, and verifying compliance with building regulations and standards regarding ventilation.

In summary, air permeability testing evaluates the overall airtightness of the building envelope, which is required under building regulations to determine which type of ventilation system to install. It is also critical for the designer in the ventilation strategy to be compliant with PAS 2035:2023. Meanwhile, background ventilation testing assesses the performance of the continuous ventilation system in providing fresh air to occupants and maintaining indoor air quality, thereby mitigating the need for additional undercuts and trickle ventilation. Both testing methods are crucial for ensuring energy efficiency, comfort, and health in buildings.