Air Duct & Dryer Vent Cleaning for Missouri's Hot-and-Cold Climate

Arctic air in winter, Gulf humidity in summer

NOAA's state climate summary explains that Missouri's interior location, with no mountain barriers to the north or south, exposes it to cold arctic air in winter and warm, moist air from the Gulf of Mexico in summer. Average temperatures differ by about 10°F from north to south, and the north averages more than 20 inches of snow a year compared with less than 5 inches in the south.

Under the 2021 IECC, most Missouri counties — including Jackson, Clay and Platte around Kansas City, St. Louis County, the city of St. Louis and Greene — are in climate zone 4A, which the DOE Building America program classifies as mixed-humid. A band of 26 northern counties is in zone 5A (cold), and two Bootheel counties, Dunklin and Pemiscot, moved to zone 3A in the 2021 update.

The same ductwork usually handles both seasons. In EIA's 2020 RECS, a furnace was the main heating equipment in about 76% of Missouri homes, and about 83% used a central air-conditioning unit, compared with about 67% nationally.

Sources: NOAA NCEI State Climate Summaries 2022 — Missouri; PNNL for U.S. DOE — Guide to Determining Climate Zones by County: Building America and IECC 2021 Updates (PNNL-33270, 2022); U.S. EIA — 2020 Residential Energy Consumption Survey, state highlights: space heating; U.S. EIA — 2020 Residential Energy Consumption Survey, state highlights: air conditioning

Basements are common — and so is basement dampness

RECS 2020 estimates that about 53% of Missouri homes have a basement, compared with about 30% nationally, and the Census Bureau reports that half of the new single-family houses completed in the Midwest in 2025 had a full or partial basement.

A basement often puts the furnace and main duct runs within easy reach, and the U.S. Department of Energy notes that ducts in a protected space such as a basement may lose somewhat less energy than a typical duct system. The trade-off is moisture: University of Missouri Extension explains that a damp basement is often caused by humid air condensing on cooler surfaces, and recommends exhausting clothes dryers outside to remove moist air.

Sources: U.S. EIA — 2020 Residential Energy Consumption Survey, state highlights: structural characteristics; U.S. Census Bureau — Characteristics of New Housing: type of foundation in new single-family houses completed; U.S. DOE — Improving the Efficiency of Your Duct System; University of Missouri Extension — How to Prevent and Remove Mildew: Home Methods (GH5928)

Older housing, especially in St. Louis

In the Census Bureau's 2024 American Community Survey, about 13% of Missouri housing units were built in 1939 or earlier, compared with 11.5% nationally. In the city of St. Louis the figure is about 56%, and in Kansas City about 20%.

Older heating systems can include materials that shouldn't be disturbed. EPA lists hot water and steam pipes covered with asbestos material, blanket or tape, and oil and coal furnaces with asbestos insulation, among places asbestos may be found, and its duct cleaning guidance says asbestos-containing materials should be disturbed or removed only by specially trained and equipped contractors.

Sources: U.S. Census Bureau — American Community Survey 2024 1-year estimates, table B25034 (Year Structure Built); U.S. EPA — Learn About Asbestos; U.S. EPA — Should You Have the Air Ducts in Your Home Cleaned?