What is the best replacement for 1950s-era ductwork in an HVAC system?


What is the best replacement for 1950s-era ductwork in an HVAC system?

Asked by Bill Seeger

The home is a 1958 2400 sf brick ranch house with a Carrier NGFA furnace, currently running at 93% efficiency, and a Carrier 2000 13 SEER air conditioning unit. The current ductwork leaks like a sieve and I would like to replace it with an insulated product. Also, I need to equalize the distribution pressure so all vents are balanced.

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Harold Remlinger, AIA, LEED AP, NCARB's picture


There may be no reason to absorb the cost for installing all-new ductwork in your home.

It is unnecessary to insulate ductwork if it is typically located within the conditioned space of the home. Even though you will have conductive heat loss due to the material of the duct, it will contribute to the overall heat gain of the space in most instances.

Here are a few reasons for the installation of insulated ducts:

  1. Insulated duct is typically installed in regions with high humidity where condensation can build on the ductwork leading to corrosion and even staining if it is above a ceiling.
  2. Insulated duct is effective in attic spaces to minimize heat loss and overheating of the attic.
  3. Also, ducts which are located in a naturally ventilated crawl space should be insulated.

If you have ductwork in one of the aforementioned configurations, it is recommended to use a minimum R-8 insulation.

Seal your ducts

Perform a smoke test on the ductwork and HVAC system to locate all leaks and use a mastic sealer or aluminum-faced duct tape to seal the leaks.

  • Leaks and cracks can lead to up to 38% of heat loss and the inability to properly balance the system.
  • You will find that this is a more cost-effective approach.

Balancing your system

After all of your leaks are sealed, you will be able to get a more accurate account as to the balance of the system.

Contact your local HVAC contractor to assess, adjust and prescribe methods of balancing your system. In most instances, manual adjustment to the dampers installed in the branch runs will correct balance problems.

For more information:

Read Elliot Seibert's Q&A "What's the best product to use to seal ductwork?"

Also, read Rick Goyette's Q&A "Should I replace metal duct in a 1950s home with the current flex duct? Or is cleaning better?"