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Energy Savings

Annual energy savings that will result from effective duct sealing will depend on several factors.  Most – typically >80% – of the savings will come from sealing the supply subsystem.  (Typically, sealing the return subsystem primarily addresses comfort issues and, secondarily, energy savings.)

The primary factors influencing energy savings are:

  • Extent of supply duct leakage
  • How much supply ducts in unconditioned space (e.g. an attic, garage, or unconditioned basement)
  • Fuel (e.g. natural gas) cost

Secondary factors include:

  • Efficiency of the furnace
  • Thermostat setting
  • External wall and attic insulation
  • Central air conditioning (if present and used, increase estimate by 10-15%)

We’ve estimated annual energy savings from duct sealing using a NYSERDA-endorsed software program and these parameters. These estimates are on the conservative side, as the software is not capable of modeling leakage into wall cavities and spaces between floors as energy waste… even though it is.

Here are some scenarios for a two-story (plus unconditioned basement) 2000-ft2 home with a furnace blower capacity of 1200cfm (cubic feet per minute), natural gas at $1/therm, and no central air. Energy savings is generally scalable to other size homes and different gas costs, so, for example, if your home is 3000-ft2 – 50% larger, simply multiply the estimated annual savings by 1.5.

Older home with typical insulation from that era, 75% efficient furnace, and thermostat set to 68F:  

Ducts in unconditioned space

70%

70%

50%

50%

Initial leakage

20%

35%

20%

35%

Estimated annual energy savings

$390-525

$570-720

$210-305

$340-450

 

Older home with typical insulation from that era, a 75% efficient furnace, and programmable thermostat set to 62F 8hrs/weekday, otherwise 68F:

Ducts in unconditioned space

70%

70%

50%

50%

Initial leakage

20%

35%

20%

35%

Estimated annual energy savings

$360-480

$530-670

$195-280

$320-420

 

Older home with typical insulation from that era, 92% efficient furnace, and thermostat set to 68F:

Ducts in unconditioned space

70%

70%

50%

50%

Initial leakage

20%

35%

20%

35%

Estimated annual energy savings

$270-360

$400-500

$145-210

$240-315

 

Typical insulation of a newer home, 92% efficient furnace, and programmable thermostat set to 62F 8hrs/weekday, otherwise 68F:

Ducts in unconditioned space

70%

70%

50%

50%

Initial leakage

20%

35%

20%

35%

Estimated annual energy savings

$145-200

$215-270

$105-140

$150-195