As a home energy efficiency expert, I have witnessed firsthand the consequences of duct leakage on a home's overall performance. Duct leakage occurs when there are gaps or holes in the ductwork that allow conditioned air to escape, resulting in higher energy bills and decreased comfort. That's why it's crucial to conduct a duct leakage test to identify and address any issues before they become bigger problems. At Priority Energy, we recently performed a duct leakage test on a 4000 square foot house that included the air handler. The results showed a leakage rate of 151 cfm at 50 pascals, which is considered a good score.
However, this score can vary depending on the size and layout of the home, as well as other factors. During the test, we did not include the dryer ventilation ducts or ERV ducts in our measurements because their leak rates would be too low to accurately measure. However, it's important to note that these ducts can still contribute to overall duct leakage and should be properly sealed. There are two ways to measure duct leakage: as a percentage or as a surface area value. The percentage rating is determined by comparing the calculated leak rate of the home to the flow rate of its air handler. The surface area value, on the other hand, provides a visual representation of the total area that is leaking and can help estimate the amount of work needed to repair it. It's not uncommon for homes to fail a duct leakage test during the construction process.
In fact, our technicians have found that most systems fail at this stage due to poor installation practices. That's why we offer an aerosol sealing service that can significantly improve airflow and overall performance once the home is finished. During the construction process, it's important to take the time and care to properly install and seal the duct system. This includes sealing every part of the system, as even small leaks can add up and significantly impact the overall efficiency of the home. According to our technician, most homes that do not undergo a duct test have a leakage rate of about 7-8 cfm per 100 square feet. However, our ducts were found to be quite narrow compared to other local offices, which can contribute to higher leakage rates. It's important to note that every time a duct is placed outside of the building envelope (such as in the attic, basement, or garage), the entire system must be tested.
This is why it's crucial for HVAC contractors to conduct a duct leakage test when replacing a furnace or air conditioner, with some exceptions based on climate, building size, and local city requirements. During the initial construction phase, most well-sealed systems will pass a duct leakage test. However, if they do not, it's still possible to locate and seal any leak points and retest. It's also important to note that during the off-season when the HVAC system is not in use, these duct leaks become passive leaks that can directly impact the home's energy efficiency. At Priority Energy, we use an external HERS (Home Energy Rating Systems) evaluator to verify that our sealing and testing of ducts has been performed correctly and that the overall leakage rate is 15% or less. This ensures that our clients are receiving the highest level of service and that their homes are performing at their best.
