A purifier on the dresser, or fix the whole house? A day of St. Augustine air-quality calls

Two choices, side by side

The plug-in purifier promises a lot for a small price: filtered air, quiet operation, an app. It filters the room it sits in, as long as the door is closed, as long as the filter is changed, and as long as the problem is particles. In St. Augustine the problem is usually water. A dresser-top unit does nothing for a house at 65 percent humidity in August, and it does nothing for the growth that humidity feeds on the coil, in the ducts and in the closets.

The whole-house approach treats the air handler as the purifier it already is: every cubic foot of air in the house passes through it several times an hour. Put the filtration, the dehumidification, the ventilation and, where it helps, the UV at that one point, and the whole house gets the benefit without a box in every room.

The second approach costs more up front and solves the problem. The first costs less and moves it around. A day of air-quality calls across the city shows how that plays out.

A typical day: morning in Lincolnville, afternoon on the island

9:00 a.m., Lincolnville. A Victorian frame house, plaster and lath, tall windows, ductless mini-splits. The complaint is dust and a musty smell in the back rooms. The particle counter reads high; the hygrometer reads 62 percent at 9 in the morning. The mini-split filters are mesh screens that catch nothing fine. The crawlspace is open and damp. The recommendation isn’t a purifier: it’s crawlspace moisture control and a whole-house dehumidifier for the main floor, with better filtration in the two heads that run the most. The dust is partly a humidity problem too; mold spores and dust mites both live on moisture.

11:30 a.m., Fullerwood Park. A 1940s Colonial Revival with retrofit ducts. The owner’s child has asthma and a portable purifier runs in the bedroom all night. Static pressure test shows a return starved for air; the duct in the crawlspace has two open joints pulling crawlspace air into the system. The purifier was fighting the house. Seal the duct, add a media filter cabinet, and the bedroom air changes more in an hour than the portable managed all night.

1:30 p.m., St. Augustine Shores. A 1985 block ranch, attic system, two large dogs. One-inch filter loaded solid in three weeks every time. A four-inch media cabinet plus a UV light over the coil, which had grown a coat over the summer. Nothing exotic.

3:30 p.m., Anastasia Island. A 2010 elevated home a block from the beach, owners present only in summer. House at 68 percent humidity when they arrive each June, closets musty, shoes furry. The system is oversized and cycles off before it dries anything. A ducted dehumidifier tied into the return, set to hold 50 percent while they’re away. Problem gone, and the vacation-rental guests in the off months stop leaving reviews about the smell.

The instruments we carry

• A hygrometer, because relative humidity above about 55 percent is the root of most St. Augustine complaints and nobody can judge it by feel.
• A particle counter, which separates “the house is dusty” from “the house is dusty with particles small enough to matter.”
• A manometer reading static pressure on the indoor unit, the fastest way to find duct leaks and starved returns.
• A thermal camera for moisture behind plaster, in crawlspaces and under the slab-on-grade ranches of the Shores.
• An inspection camera for duct interiors.
• A carbon monoxide meter for every house with gas appliances or an attached garage.

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What the meters usually show

What we recommend, and what we don’t

We’re a Lennox dealer and the Healthy Climate line gives us filtration, purification, humidity control and ventilation that integrates with the air handler. We install media filters, whole-house air cleaners, UV lamps, whole-home dehumidifiers and energy recovery ventilators, and we service duct systems. We also test; an air-quality audit of the house with written results comes before any equipment is proposed.

What we won’t do is sell a purifier into a humidity problem, a dehumidifier into a duct-leak problem, or any equipment into a house we haven’t measured. Vacation-rental owners on Anastasia Island, retirees in the Shores and families in the historic districts all get the same first step: the instruments come out, and the recommendation follows the numbers. Equipment add-ons on a new system qualify for the same financing as the system itself; terms are explained at the quote, never on this page.