Why summer humidity is the main driver
Virginia summers are humid. From June through September, the outdoor air carries a heavy moisture load.
Your air conditioner pulls that air in, cools it, and pushes it through the ducts. Some moisture condenses near the evaporator coil and drains away. But some of it stays in the ductwork after the unit shuts off.
Flex duct has a soft fibrous inner lining. That lining holds moisture longer than bare sheet metal. Warm and damp duct walls are where mold starts.
We see it most often near the air handler. The first few feet of duct off the main trunk are where it tends to take hold first.
What pollen seasons leave in your return ducts
Chesterfield County sees heavy pollen every spring. Tree pollen arrives in March and April. Grass pollen follows in May and June.
Ragweed runs from late summer into fall. Your return ducts pull air from every room in the house. When pollen counts are high, some of it gets drawn into the duct system.
Running the fan while windows are open speeds this up. Over a few seasons, pollen builds up on the duct lining and on the blower wheel. Fine particles that slip past your filter settle inside the runs and stay there.
The buildup on the blower wheel is worth calling out separately. A coated blower wheel moves less air per spin than a clean one. The whole system has to work harder to hit the temperature you set.
What freeze-thaw cycles do to duct joints
Midlothian winters are mild by most standards. We still get several rounds of freezing and thawing between November and March.
Those temperature swings cause metal ductwork to expand and contract with each cycle. Over the years, joint tape dries out and flexible connections loosen. A loose joint lets in air from the crawl space or attic.
Most crawl spaces in Midlothian stay damp through winter. That damp air raises the moisture level inside the duct runs. Attic air carries insulation fibers, and neither source belongs in your air supply.
Homes built before 1990 carry the heaviest buildup
The median owner-occupied home in Midlothian is about 41 years old. Most ductwork here was installed at or near that time.
Original flex duct from the 1980s degrades over time. The inner lining becomes brittle and can crack. When it does, material from inside the duct wall works its way into the air stream.
If your home was built before 1995, the ducts have likely never been professionally cleaned. That is four decades of Virginia summers, pollen seasons, and freeze-thaw cycles moving through the same runs.
When sanitizing makes sense and when it does not
A standard cleaning uses negative pressure and brushes to pull debris out of the ducts. A sanitizing treatment applies an antimicrobial coating to the duct walls after the cleaning.
We recommend sanitizing when we find mold on the duct walls. We also recommend it when the home has had water intrusion, or when previous owners kept pets. Those situations leave biological material that brushing and suction alone will not remove.
If the duct walls are dry and we see no mold on inspection, a standard cleaning is enough. You do not need sanitizing on every visit. For more on this, see our indoor air quality FAQ.
What we find when we open vents in this area
We clean ducts across Chesterfield County on a regular basis. What we find follows a consistent pattern based on when the home was built.
Homes from the 1980s tend to have thick compacted dust mixed with degraded lining material. Homes from the late 1990s and 2000s usually show heavy pollen layers and occasional mold near the coil.
Homes that have had renovation work almost always have drywall dust deep in the duct runs. That fine dust travels farther than most people expect, and it settles on every surface inside the system.
If any construction happened in your home in the last two years, the ducts need a reset. See our move-in duct reset FAQ for what that covers.
Nearby areas we serve
We work throughout Chesterfield County and the greater Richmond area. We also clean ducts in Richmond, Brandermill, Bon Air, and Tuckahoe.