ECM: Space Heating & Cooling

Information by State  Print version   CAUTION STATEMENT TURN OFF UTILITIES: Turn off electricity, gas, propane, and other utilities before starting repairs, cleaning, or installations to avoid accident or injury. BE AWARE OF LEAD-BASED PAINT HAZARDS: Many residences built before 1978 have paint that contains lead, which can pose a serious health hazard if paint, chips, and dust are not handled properly. See the U.S. Environmental Protection Agency (EPA) lead brief before disturbing painted surfaces in homes of this vintage. Follow the HUD “Lead-Safe Housing Rule” for requirements for notification, evaluation and reduction of lead-based paint hazards. BE AWARE OF ASBESTOS HAZARDS: Homes older than 1977 may have building products that contain asbestos such as insulation, high-temperature gaskets, roofing and siding shingles, and vinyl sheet flooring. See the EPA asbestos brief before disturbing such materials. BE AWARE OF MOLD AND MOISTURE HAZARDS: Molds can gradually destroy materials they grow on; can irritate the eyes, skin, nose, throat, and lungs of both mold-allergic and non-allergic people; can cause asthma attacks in people with asthma who are allergic to mold; and can cause other serious health problems. To learn more about preventing and cleaning up mold in homes, see these mold guides and the EPA brief on What to Wear When Cleaning Moldy Areas.

H9. Seal and Insulate Ducts

Description

In buildings with forced-air heating (or cooling) systems, warm (or cold) air is distributed to each room through flexible or sheet metal ductwork. The air travels from the furnace, heat pump, or air conditioner through a supply duct to each room, and it returns to the furnace or heat pump through a return duct to be heated (or cooled) again. 

Forced-air distribution systems can lose energy in two ways. First, uninsulated ducts running through unconditioned spaces such as basements, crawlspaces, and attics loose energy through conduction. Second, ducts lose energy through leaks, or convection. Studies show that duct leaks typically raise a home’s heating and cooling costs by 20-30 percent. That figure can double in homes where ducts are not insulated. When supply ducts leak to an unconditioned space, less air reaches the room or apartment. To make matters worse, because not enough air is reaching the conditioned space, the room or apartment may become depressurized, which causes outside air to rush into the space through any path it can find, such as around windows or doors. The furnace (or air conditioner) then has to work harder to heat or cool the space.

When return ducts have leaks, air from unconditioned spaces enters the return duct, reducing the amount of heated (or cooled) air that can enter it through the return grille. Because air cannot leave the room through the grille, the room or apartment becomes pressurized, and the air, seeking another escape route, squeezes its way to the outside. Not only do leaky return ducts waste energy, but they can cause indoor air quality problems as fumes from combustion appliances, vapors from household cleaners stored in the basement, and soil gases such as methane enter the conditioned space.

To cut energy waste, ducts should be sealed to eliminate any leaks, and then wrapped with insulation. The first step to sealing ducts is to diagnose where the leaks are. This process requires diagnostic tools such as blower doors or pressurization devices and should be done by experienced technicians.

Applicability

• Single-family and multifamily buildings with forced air heating or cooling 

Types

• Ducts
  • metal
  • rigid fiberglass
  • flexible
• Duct insulation
  • fiberglass batts
  • blown rockwool, fiberglass, and cellulose
  • rigid fiberglass
• Sealer
  • mastic

Considerations

• Pressurization tests help identify duct leaks.
• Ducts should be sealed with mastic.
• Duct sealing should only be done by a trained technician.

Performance/Economics

• Duct insulation and sealing reduce heating and cooling costs between 20–30 percent.
• Duct sealing reduces the amount of outdoor pollutants siphoned from the outdoors.

Resources/Links

Energy Conservation for Housing – A Workbook, HUD, September 1998. Pages 7-75 through 7-77 address sealing and insulating duct systems.

Improving Energy Efficiency in Apartment Buildings, American Council for an Energy-Efficient Economy, 1995. ISBN 0-918249-23-6. Pages 86 through 88 address sealing and insulating electric heating duct

Consumer Guide to Home Energy Savings, American Council for an Energy Efficient Economy, 1999, ISBN 0-918249-38-4. Pages 80 and 84 address duct insulation and sealing.