How do you measure air tightness and infiltration in buildings?

Air tightness and infiltration in buildings are typically measured using a technique called blower door testing. A blower door is a powerful fan that is temporarily installed in an exterior doorway of the building. The fan depressurizes the building, causing air to flow in through any unsealed cracks or openings. During the test, the airflow rate required to maintain a constant pressure difference between the inside and outside of the building is measured. This airflow rate, along with the size of the building envelope, is used to calculate the air tightness of the building, often expressed in air changes per hour (ACH) or cubic feet per minute per square foot of envelope area (CFM/sqft).

This is one of the most common methods used to measure air tightness in buildings. A blower door is a powerful fan that is temporarily installed in an exterior doorway. By depressurizing or pressurizing the building with the blower door, technicians can measure the airflow rate required to maintain the pressure difference between the inside and outside of the building. The results are typically reported as air changes per hour (ACH) or air leakage rates in cubic feet per minute (CFM) per square foot of building envelope area.

Tracer gases, such as sulfur hexafluoride (SF6) or helium, can be released into a building to quantify air infiltration rates. These gases are inert, non-toxic, and non-flammable, making them safe for indoor use. By measuring the concentration of tracer gas inside the building over time, technicians can calculate the air exchange rate and identify areas of high infiltration.

Pressure tests, such as the Zone Pressure Diagnostics (ZPD) or Perfluorocarbon Tracer (PFT) method, measure the pressure differentials between various zones within the building to assess air movement and leakage paths. These tests help pinpoint areas of high-pressure differentials, indicating potential air leakage or infiltration points that may compromise the building's air tightness.

Flow measurement techniques, such as smoke pencils or fog machines, visually indicate airflow patterns and identify areas of air movement through drafts or leaks in the building envelope. These qualitative methods complement quantitative tests like blower door tests by providing visual confirmation of air leakage pathways and infiltration points.

Thermal imaging cameras detect temperature differentials associated with air leakage and infiltration, allowing for non-invasive identification of heat transfer through building surfaces and cracks. By capturing infrared images of the building envelope, thermal imaging helps identify areas of heat loss or gain associated with air leaks, providing valuable insights into energy efficiency and air tightness.

Smart sensors equipped with wireless connectivity and cloud-based analytics enable remote monitoring and management of air tightness and infiltration levels. Building automation systems can use data from these sensors to optimize HVAC operation and ventilation rates in real-time, ensuring optimal indoor air quality while minimizing energy consumption.

Building energy modeling software, such as EnergyPlus or COMSOL Multiphysics, can simulate airflow and infiltration rates based on building geometry, construction materials, and environmental conditions. These simulations enable virtual testing of different building design scenarios and mitigation strategies to optimize air tightness and minimize infiltration, providing valuable insights for design optimization and performance prediction.