H1. Install Vent Dampers

Description

All oil and gas furnaces and boilers have a vent (flue or chimney) to discharge unwanted combustion gases to the outside. A vent damper is a device installed in the vent of a furnace or boiler that automatically closes the vent when the burner goes off to reduce the loss of warm air up the chimney. Vent dampers save money by reducing the amount of heat loss through the chimney during this off cycle. (Note: Codes do not allow flue dampers--that is, dampers installed upstream of the draft diverter or barometric damper--as a retrofit, although flue dampers can be installed on some appliances at the time of manufacture. Unlike flue dampers, vent dampers are installed downstream of the draft diverter.)

The level of savings from a vent damper depends on several factors. In general, savings tend to be higher with larger, older, oversized boilers because their off-cycle losses are greater. Savings also depend on the absence of alternate escape routes for the hot air, such as out a crevice in the basement or up a neighboring water heater vent. If the hot air finds its way out of the building despite the vent damper, savings will be lower.

Applicability

• Single-family and multifamily buildings
• Oil- or gas-fired boilers or furnaces with atmospheric burners without vent dampers or flue dampers

Types

• Mechanical
• Thermal

Considerations

• Before a vent damper is installed on a gas boiler or furnace, a PHA should make sure that the burner has an electronic ignition. Installing a vent damper on a system with a standing pilot light may cause safety concerns.
• The vent damper should include a control that prevents the boiler or furnace from operating when the vent damper is in the closed position.
• Contractors must be certified to install vent dampers.

Performance/Economics

• Leak tight mechanical dampers are most effective.
• Thermal vent dampers are not recommended since they do not allow accurate timing.
• Vent dampers reduce heating costs by approximately 5 to 8 percent.

Resources/Links

Energy Conservation for Housing – A Workbook, HUD, September 1998. Pages 7-37 through 7-39 address air infiltration and leakage.

Improving Energy Efficiency in Apartment Buildings, American Council for an Energy-Efficient Economy, 1995. ISBN 0-918249-23-6.Pages 98 through 103 address infiltration and air leakage measures in apartment buildings. 

Consumer Guide to Home Energy Savings, American Council for an Energy Efficient Economy, 1999, ISBN 0-918249-38-4. Pages 11 through 17 address strategies to control air leakage.

Insulation and Air Sealing. Part of the U.S. Department of Energy's Consumer's Guide. Discusses both air leakage and moisture control.