Duct Leakage Test San Antonio - Testing to determine air leakage

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What is a Duct Leakage test?

A Duct Blaster is a machine that Energy Professionals use to diagnose any air leakage inside a home’s air ducts.  This leakage is measured in Cubic Feet per Minute (CFM), and a duct blaster is used to find this measurement. The Duct Blaster will pull air out of the duct system (depressurize) and through the fan.  The amount of air that is measured is the amount of leakage in the ducts.

To set up our testing, a technician will cover up all of the supply and return air registers in the house with tape or a cover. Then the duct blaster will be connected to the return register with tape.  This process usually takes around 30 minutes to set up.  Once all registers are sealed, the technician will turn on the machine and read the results on the manometer gauge. 

Duct Leakage Test

What does a Duct Leakage test tell us about a home?

The duct leakage testing result will identify if the duct system is leaking air and how much air.  If your duct system leaks air into the attic through the supply ducts, you could depressurize your house and draw air from outside the house into the conditioned space.  If you are leaking air in the return side of the system, you could be pressurizing the house and pushing air out of the gaps and cracks of the home.

Typically, with existing homes, the results from our tests must show less than 10% duct leakage.  International Energy Conservation Code (IECC) requires less than 3% – 4% duct leakage for new home construction, depending on the climate zone. 

Do you need help clearing permits or complying with inspections for your city? Lone Star works with homeowners and builders all over San Antonio (and surrounding cities) to help them through this process through our testing. We aim to help all of San Antonio and its surrounding cities improve the energy efficiency of their homes. The air quality can be affected when there is a leak present in the air duct. We ensure your house’s air duct system is tested properly to keep the bills lower due to the San Antonio heat.


There are several ways to test duct leakage. The most common method is to use a blower door. This device creates a tight seal around the door frame and uses a fan to create negative pressure inside the house. This pressure difference causes air to leak into the home through gaps in the ductwork. It is possible to calculate the total amount of leakage by measuring the airflow. Another method is to use a smoke pencil. This device emits a small amount of smoke drawn through the ductwork by the forced air. Any holes or leaks will be visible as streaks of smoke. Finally, it is also possible to conduct a pressure test by temporarily sealing all openings in the ductwork and measuring the pressure difference with a manometer. Following these steps makes it possible to test for duct leakage accurately. It is important to check the equipment before testing and to use the proper blaster test flow.

A duct blaster test is a quick and easy way to measure the effectiveness of your home’s HVAC setup. The test involves sealing all of the ducts in your home and then connecting a powerful fan to one of the sealed ducts. The fan is turned on, and the duct pressure is measured. The pressure is then compared to the amount of airflow from the fan. If the pressure is too low, there is a leak in the ductwork. The test can determine whether your ducts need to a repair or to be replaced.

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