The article has been updated successfully.Major leaks can be found around joints at ductwork connections, around the air handler, and near vents. Look for holes, tears, and loose joints.
Every unsealed joint is likely a small leak—even if a gap is not visible. Make sure registers and vents are firmly attached. If your home has a mechanical closet, it should also be properly sealed to prevent negative return side air leakage. The return chamber should be kept free of debris.
Source: Wendell A. Porter, Hyun-Jeong Lee, and Kathleen C. Ruppert, The Duct System, UF/IFAS FCS3263, 2008.
Additional Resources
UF IFAS Energy Efficient Homes: The Duct System - http://edis.ifas.ufl.edu/FY1024
Florida Building Code - http://www.floridabuilding.org
U.S. Department of Energy – Better Duct Systems for Home Heating and Cooling - http://www.nrel.gov/docs/fy05osti/30506.pdf
U.S. Department of Energy – Improving the Efficiency of Your Duct System - http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/27630.pdf
U.S. Department of Energy – Minimizing Energy Losses in Ducts – http://www.energysavers.gov/your_home/space_heating_cooling/index.cfm/mytopic=12730
