Duct Cleaning in Older Missouri Homes: What to Check First

How old is Missouri's housing?

The share of housing units built in 1939 or earlier, from the Census Bureau's 2024 American Community Survey:

Source: U.S. Census Bureau — American Community Survey 2024 1-year estimates, table B25034 (Year Structure Built)

What older duct systems can look like

The U.S. Department of Energy describes several arrangements that turn up in existing homes. Builders sometimes use the spaces between basement or ceiling joists as ducts, and using parts of the building structure is even more common for returns. Some homes have no return ducts at all; the furnace draws basement air in through an intake grille.

DOE notes that joist-space ducts are likely to be uninsulated and may have leakage paths to the outside. Cleaning can remove accumulated dust and debris from the parts that can be reached, but it doesn't change how a system was built. Questions about redesigning returns or sealing leaks belong with a heating and cooling contractor.

Source: U.S. DOE — Improving the Efficiency of Your Duct System

Materials to leave alone

EPA lists hot water and steam pipes coated with asbestos material or covered with an asbestos blanket or tape, and oil and coal furnaces and door gaskets with asbestos insulation, among the places asbestos may be found.

Its advice is to leave undamaged asbestos-containing materials alone, to treat a material as if it contains asbestos when in doubt, and to have a trained and accredited asbestos professional take samples. EPA's duct cleaning guidance adds that asbestos-containing materials should be disturbed or removed only by specially trained and equipped contractors. A duct cleaning crew should not be the one deciding what a wrapped pipe is made of.

Sources: U.S. EPA — Learn About Asbestos; U.S. EPA — Protect Your Family from Exposures to Asbestos; U.S. EPA — Should You Have the Air Ducts in Your Home Cleaned?

Basement access and what to expect

RECS 2020 estimates that about 53% of Missouri homes have a basement. DOE notes that finding the furnace should be no problem when it's in the basement, and exposed trunk lines in an unfinished basement can be reached directly. Branch runs above finished ceilings or inside walls are reached through registers and existing openings where possible; anything that can't be reached is noted in your written estimate rather than skipped without mention.

• Clear a path to the furnace and to each register and return grille.
• Point out any wrapped pipes, old boiler or furnace components, or past water leaks near the ductwork.
• Mention recent renovation — EPA advises sealing registers and not running the system during dusty work until the dust is cleaned up.

Sources: U.S. EIA — 2020 Residential Energy Consumption Survey, state highlights: structural characteristics; U.S. DOE — Improving the Efficiency of Your Duct System; U.S. EPA — Should You Have the Air Ducts in Your Home Cleaned?

Questions to ask before any duct cleaning

These questions come straight from EPA's guidance and apply to any provider, including us.

• Which components are included? EPA warns that failing to clean a component of a contaminated system can re-contaminate the whole system.
• Is there a clear reason to clean? EPA suggests considering it for substantial visible mold in hard-surface ducts, vermin, or excessive dust and debris, or particles actually coming out of the supply registers — and it notes that duct cleaning has never been shown to actually prevent health problems.
• Will chemicals be used? EPA notes research hasn't demonstrated the effectiveness of biocides or sealants in duct cleaning; our standard service is mechanical cleaning only.
• What can't be reached, and why? That should be written down before work starts.

Source: U.S. EPA — Should You Have the Air Ducts in Your Home Cleaned?