2.2e Efficient Ducts

Feature	Ducts that move air throughout a home without causing a loss of energy are part of a green-home strategy. In this photo, you see ducts running through open-web ceiling joists between levels. The band joist of exterior walls will be sealed with spray foam insulation so the space between floors is truly within the air barrier skin and thermal (insulation) envelope of the building. (Source: LSU AgCenter)
Function	To create a comfortable and energy-efficient home, an efficient duct system is a must. Ducts—known collectively as the air distribution system—carry air from the central heater or air conditioner to each part of the home and back again. In a typical house about 20% of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts. (Source: Energy Star)
Benefits	• Improved Comfort. When ducts are properly sealed and insulated, they deliver conditioned air more effectively to all rooms—helping to ensure a more constant temperature throughout the home. • Lower Utility Bills. The average homeowner spends about $1,000 on space heating and cooling each year. Tightly sealed and well-insulated ducts found in Energy Star-qualified homes can reduce annual utility bills by $120 or more.  • Improved Indoor Air Quality. Leaky ducts in attics, unfinished basements, crawl spaces, and garages can allow dirt, dust, moisture, pollen, pests, and fumes to enter the home. Sealing these ducts helps improve indoor air quality.  • Lower Equipment Costs. When ducts are leaky, the heating and cooling system has to work harder to condition the home. Duct sealing, along with proper insulation, allows the installation of a smaller, less costly heating and cooling system. (Source: Energy Star)
How It’s Done	Techniques and practices that provide an efficient and effective duct system include: • Ducts in Conditioned Spaces. Ducts operate more efficiently in conditioned air at room temperature. They do not work as well in excessively hot or cold attics and crawl spaces.  • Sealed Ducts. EPA promotes the use of mastic and/or Underwriters Laboratory (UL) 181 approved tapes, such as metal-backed tape, to seal ducts. These materials more effectively seal leaks around duct joints and seams than standard “duct tape.” • Insulated Ducts. Leaky ducts and poorly sealed connections can waste 20% or more of the air that an occupant pays to heat and cool. To minimize this energy loss, EPA first recommends installing ducts in conditioned spaces. Where this is not possible, ducts should be insulated as recommended by the International Energy Conservation Code (IECC). Right-sized Ducts. Ducts in Energy Star-qualified homes are sized based on the Air Conditioning Contractors of America (ACCA) Manual J and Manual D calculations. This helps to ensure that the ducts accommodate the airflow requirements of the heating and cooling system for efficient distribution of heated or cooled air.  (Source: Energy Star)
More	Also, see typical places where ducts leak