“ When we think about saving energy, we commonly focus on the furnace and air conditioner units, but a leaky duct system can reduce your climate control system’s efficiency 20% to 30%



Central air conditioning and heating are the top energy consumers in California homes, so ensuring the efficiency of your entire HVAC system can yield big improvements in energy efficiency. When we think about saving energy, we usually focus on the furnace and air conditioner units, but a leaky duct system can reduce your climate control system’s efficiency 20% to 30%. These leaks can bring unwanted dust, unconditioned outdoor air and humidity into your living space-and take money straight out of your wallet.


If your home is over seven years old, have your ducts professionally tested by a certified Home Energy Rating System (HERS) technician. Duct testing is also advisable whenever heating and air conditioning units undergo a diagnostic tune-up. Duct testing is recommended for any building where a forced air heating or air conditioning system is used.



Duct pressure keeps hot or cold air flowing evenly to all registers (air vents) in the system. Without proper pressurization, registers closest to the furnace or air conditioner receive most of the conditioned air; Registers that are the furthest away receive very little airflow. If the return ducts are leaky, contaminated air from damp basements, wet crawl spaces, and attic areas that may contain animal droppings or hazardous insulation materials may infiltrate your systems. Damp wet air pulled into your system from leaking ducts condenses, and condensation can lead to mold growth. Mold growth can lead to health problems and more.

The most reliable way to find out if your ducts are leaking is to have a duct test performed by a qualified technician using the proper test equipment. The building code now requires independent verification of proper duct installation in new buildings that have forced-air heating or air conditioning, when a new central air conditioner or furnace is installed, or in renovations that will add or change over 40 feet of ducts. Home Energy System (HERS) raters are certified by the California rating services, including accurate duct leakage tests.

T test duct integrity, HERS raters seal the duct registers and returns (vents where the air goes in or out), then pressurize the system using a calibrated blower to blow air into the duct. A probe placed inside the duct measures the airflow and indicates the amount of leakage. Results can range from locating small leaks to discovering that entire duct sections have become disconnected from the system.

When duct testing reveals leaks in new construction, it is the contractor’s responsibility to fix the leaks. Homeowners can repair some types of leaks found in older buildings by reconnecting ducts that have become completely disconnected, for example. If you decide to repair your own duct system, you should always wear a respirator when working in an attic space. If your system requires more than a basic repair, it will be most efficient and effective to hire an experienced heating and air conditioning contractor to seal, repair or replace ducts.

In buildings with more than one story, focus on repairing ducts in the roof ceiling space first. Leaking duct work in a ceiling space between floors is not as bad as leaking ducts in the roof ceiling space or in an unconditioned zone (like the attic) with an exterior or roof exposure. The temperature difference from the adjacent conditioned spaces will be significantly higher in spaces just below the roof, so there will be a greater impact on the equipment efficiency.


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