Clean the ducts or seal them? The Gainesville answer depends on the attic and the pollen count

Two problems that look the same from the living room

Picture two homeowners. The first lives in a 1986 house in Haile Plantation. The ducts are original flex, the filter has been a thin fiberglass pad for decades, and the family dog has shed through every one of those years. A camera inside the supply trunk shows a grey felt of dust and pollen. Cleaning is the right call.

The second lives in a 1979 ranch in Northwest Gainesville. The dust is just as bad, but the camera shows the ducts are fairly clean inside. The streaks around the ceiling registers, the attic-smell when the system starts and the summer humidity that never drops below 58 percent all point to the same cause: joints that have pulled apart in forty years of attic heat and return boots that were never sealed. Cleaning would leave every one of those problems in place. Sealing fixes them.

The Gainesville housing stock produces both cases in volume. Nearly one home in five dates from the 1970s and another sixth from the 1980s, and most still carry their first ductwork. Add a tree canopy that drops pollen from late January into May and a climate that keeps attics saturated all summer, and the ducts are often the dirtiest and leakiest part of the house at once.

What the climate does to Gainesville ducts

• Attic heat. Summer attics in the city reach 130 degrees. Duct tape dries and lets go; mastic that was never applied cannot fail because it was never there. Flex duct inner liners crack where they bend.
• Humidity. Any cold supply duct with a gap in its insulation sweats in the attic. Wet insulation sags, grows mold and stains ceilings.
• Pollen and canopy. Oak and pine pollen that gets past a thin filter settles in the first horizontal run. Leaf litter and insect debris come in through leaking returns.
• Crawlspaces. Under the historic homes of the Duckpond and Pleasant Street, return ducts run through damp ground air and pull it in at every seam.
• Student turnover. Rentals near campus go years without a filter change, and the ducts become the filter.

What leaks and dirt do to the equipment

Leaky ducts make the air conditioner run longer to cool the same rooms, which is the hidden line on many GRU summer bills. Return leaks pull hot attic air across the coil and raise indoor humidity. Dirt on the coil and blower, delivered by ducts that let it through, cuts airflow and can freeze the coil in August. None of this is dramatic; all of it is expensive over a season.

GRU sells a residential duct test, $80 for a pre-test or $150 for a before-and-after pair, that puts a number on leakage. Its LEEPplus program has sealed and repaired ducts at no cost for income-qualified owners of homes over ten years old, though new applications were paused as of May 2026. Clay Electric members can include duct repair in its Energy Smart loan program. Where Cook’s stands as an enrolled contractor under any of these is a question for the estimate. [[CONFIRM WITH JERRY]]

Book a duct inspection

Negative pressure and agitation: the Cook’s method

1. Camera and pressure first. A camera into the supply and return trunks shows what is inside; a leakage test shows what is escaping. The two readings decide the job.
2. Cleaning, when the ducts are dirty and sound. Furniture and floors covered. Registers removed and cleaned. A negative-pressure vacuum attached to the trunk while rotating brushes and compressed air agitate each run toward it. The blower compartment and coil cleaned at the same time, because clean ducts feeding a dirty coil accomplish nothing. Registers reinstalled, filter replaced.
3. Sealing, when the ducts leak. Mastic and mesh at every accessible joint, collar and boot; new collars where flex has pulled off; insulation repaired where it has sagged or soaked. Return plenums sealed to the air handler. Leakage re-tested.
4. Both, often. The 1980s Haile Plantation house that needs cleaning usually has leaks too.
5. Replacement, sometimes. Crushed, undersized or mold-saturated runs are replaced rather than cleaned. We say so when we find it.
6. Report. What was found, what was done, the leakage numbers before and after, and photos from the camera.

Keeping them that way

A cleaned and sealed duct system in Gainesville stays that way with three habits. Change the filter on a pollen-aware schedule, monthly from late January through April. Keep the coil and blower clean with twice-yearly maintenance, because that is where the next layer of dirt would come from. And ask us to look at the ducts during each tune-up; a connection that has started to pull loose is a five-minute fix in March and a sealing job in September. Cook’s picks up at every hour of a Gainesville night and charges the same on weekends, and we serve Gainesville, Alachua, Newberry, Hawthorne and the rest of the county from the company’s headquarters in Palm Coast.