As an expert in the field of HVAC systems, I have seen firsthand the impact that duct leaks can have on a building's energy efficiency and overall comfort. That's why it is crucial to have a standard for duct testing in place, to ensure that these issues are addressed and resolved. Both the International Energy Conservation Code (IECC) and the International Residential Code (IRC) require that duct testing be performed at a pressure of 25 pascals (Pa) or 0.1 inches. This is done using a specialized tool called a duct tester, which includes a fan, pressure gauge, and supplies to seal all HVAC vents and create a closed system. The process of duct testing involves connecting the test equipment to a return vent or controller, and then sealing off all other vents in the system. This creates a controlled environment where the pressure can be measured accurately.
However, if the test equipment is located within the area normally conditioned by the system, a door or window must be opened to allow for outside air pressure. This ensures that the pressure inside the duct network is not affected by external factors. But why is it necessary to check for duct leaks if the ducts and air treatment device are located in a conditioned space? The answer lies in the fact that leaky ducts can be a major source of energy loss and comfort problems. In addition, they can also contribute to moisture problems, especially when the ducts pass through unconditioned spaces such as ventilated attics or mezzanines. Studies have shown that on average, 3-inch low-pressure WG pipes leak eight times more than 4-inch pressure pipes. This is due to loose connections where sections of the duct connect to each other or to other components such as duct covers, trunk lines, or the air handler.
These small slits can allow air to leak out, reducing the efficiency of the system and causing discomfort for occupants. There are two types of pipeline tests that can be performed: pressure or pipeline leak (DP) tests and pressurization tests for external leaks (TALL). These tests are crucial in identifying any leaks in the duct system and allowing for proper repairs to be made. In the past, manual sealing methods were used to address duct leaks. However, a 2001 study by Oak Ridge National Laboratory found that aerosol technology is 50% more effective at sealing duct leaks and can reduce labor time and duct sealing costs by 70%. This method is preferred by many builders, especially those who install attic ducts, as it allows for easier access to the ducts. Some builders may choose to wait until the end of the construction process to test the ducts.
However, this can be risky as other professionals may have moved the ducts in the meantime, making them less accessible. It is best to test for duct leaks during the construction process when it is easier to access and seal any leaks that are found. During the testing process, it is important for the evaluator to visually inspect the ducts during disassembly. This ensures that they are completely isolated and that the insulation is not compressed by tight belts, truss elements, or excessive flexion. The evaluator must also ensure that supply ducts have an R-value of 8 and return and other ducts have an R-value of 6.The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has taken duct testing to a new level with their SPC215P standard.
This standard specifies the methods that should be used to test for leaks in duct systems, ensuring consistency and accuracy in the testing process. If any leaks are found during the testing process, the HERS evaluator or builder can perform an optional additional test using an anti-duct gun or a smoke machine to detect and seal any air leaks before installing drywall. This ensures that the duct system is properly sealed and will not cause any issues in the future. It is also important to note that if the duct leak test is performed underground, a HERS evaluator must confirm and document that the total leak in the ducts is less than or equal to 4 CFM 25 per 100 square feet of conditioned floor area or 40 CFM25 using a testing protocol approved by Resnet. They must also visually inspect and verify that the duct covers are properly sealed at the end. The standard for duct testing is not only important for new construction, but it also applies to existing homes. It is crucial for homeowners to have their ducts tested for leaks to ensure energy efficiency and comfort in their homes.
