A better filter or sealed ducts: which one fixes the dust in a Lakeside house?

Filter it or seal it: two routes to the same dust

A homeowner in Lakeside notices the dust is back a day after cleaning. Two neighbors have told her two different things: one says get a better filter, the other says the ducts leak and need sealing. Both can be right, and the house decides which.

The filter route assumes the dust is coming through the system from inside the house, from skin, fabric, pets, cooking and whatever walks in on shoes, and the filter is letting it through. A one-inch fiberglass filter stops almost nothing. A pleated one-inch filter stops more but chokes the blower on a system that was designed for the fiberglass one. A four-inch media filter in a proper cabinet stops a great deal and barely restricts the airflow. If the dust is fine, grey and everywhere, this is the route.

The sealing route assumes the dust is coming from outside the living space, from the attic, through leaks on the return side of the ductwork. The return duct in a 1980s Lakeside or a 1970s Bellair house runs through an attic full of insulation fibers, pollen and whatever the roof lets in, under negative pressure, and every gap in it pulls attic air into the house. The best filter in the world sits downstream of some of those leaks. If the dust is coarse, fibrous or yellow in spring, or if the bill is high and the far rooms never get comfortable, this is the route.

Many houses need both, in that order: seal the leaks, then filter what is left. Buying a filter upgrade for a house with a torn return is the most common wasted purchase in the county.

The checklist before you spend anything

1. Pull the filter and look at it. If it’s loaded with grey fuzz after a month, the house is dusty from inside. If it’s clean but the house is dusty, the dust is bypassing it, which means duct leaks or a filter rack that doesn’t seal.
2. Check the filter rack for gaps. A one-inch filter in a rack with a quarter-inch of daylight around it filters a quarter less than you think.
3. Walk the returns with a tissue. Hold it at each return grille with the system running. If it pulls hard at one and barely at another, the ducts are telling you something.
4. Note when the smell happens. At start-up only: coil. All the time: ducts or something in the house. After rain: a wet attic or crawlspace.
5. Read the humidity. A cheap hygrometer in the bedroom. Above 60 percent with the system running normally means the equipment is oversized or the house needs dedicated dehumidification; Oakleaf and Fleming Island houses do this.
6. Look at the bathroom fans. In many 1990s Orange Park South houses they vent into the attic, not outside, and that moisture ends up in the insulation the return is pulling through.
7. Count the pollen. From February through May the oaks and pines coat everything in Clay County. If the indoor dust turns yellow in spring, outside air is getting in somewhere it shouldn’t.

Where the checklist stops

Stop and call when the filter is clean and the house is dusty, when the humidity stays above 60 percent, when the smell is there all the time, when anyone’s breathing is worse at home than away, or when the tissue test shows a return that pulls almost nothing. Those are instrument problems now, and the instruments are on the truck.

Have the air measured

What Cook’s does on an indoor-air visit

• Measure before recommending. Humidity and temperature by room, particle counts indoors and out, static pressure at the air handler, carbon monoxide where anything burns fuel.
• Test the ducts for leakage when the readings or the house’s age point there, and find the leaks, not just the number.
• Open the equipment. Coil, pan, blower wheel, filter rack.
• Fix in the right order. Seal first where sealing is needed. Then filtration sized to the blower, not to a catalog. Then a UV lamp over the coil where the start-up smell lives. Then a whole-home dehumidifier for the tight houses that hold moisture. Then, in the tightest new construction, an energy recovery ventilator to bring in dry outside air without the humidity.
• Lennox Healthy Climate equipment for the filtration, purification and humidity pieces, registered in your name, with the same no-after-hours pricing as every other visit.

Well-water households in Middleburg, Clay Hill and the lakes get one more step: a look at any humidifier, condensate pump or evaporative device for scale, because iron and sulfur water fouls them quickly.

After the work: the next pollen season

The test of an indoor-air fix in Clay County is the following spring. From February to May the oaks and pines drop enough pollen to turn a car yellow overnight, and a house that was sealed and filtered properly in the fall comes through it with clean windowsills and a filter that loaded the way it should. The habits that hold it: check the media filter monthly in spring, keep the house closed and the fan on circulate during the heaviest drop, run the dehumidifier at 50 percent from May onward, and have the coil looked at during the spring tune-up so the start-up smell never gets a chance to return. A year later the dust question has an answer, and it is usually neither neighbor’s.