The May morning in Tomoka Oaks when the hygrometer read 68 percent

The scenario

A couple in Tomoka Oaks, in one of the early-1960s ranches on the old golf course side, call in the last week of May. The house has had a new air conditioner for two years, installed after Ian put water in the garage, and it is a good unit. But the mornings are wrong. The sliding doors to the lanai sweat on the inside, the closet by the bathroom smells like a boat, and the hygrometer they bought online reads 68 percent at breakfast. The thermostat says 75. It does not feel like 75.

The cause is the calendar. In late May the rains have started and the dew point outside is near 70, but the afternoons only reach the mid-80s. The air conditioner runs a few minutes at a time to hold 75 and shuts off long before it has wrung the air out. The house is cool and wet, and in a riverfront neighborhood whose slabs and walls are still giving back moisture from two floods, wet is the condition that grows mold.

What we recommend

A ducted whole-house dehumidifier, installed in the garage beside the air handler and tied into the return and supply ducts, controlled by its own humidistat. It runs when the humidity is high regardless of whether the thermostat is calling, which is exactly the gap the air conditioner leaves in May, October and on every rainy summer night. Set to hold about 50 percent, it ends the sweating doors and the closet smell within a few days.

We do not recommend going back to an oversized air conditioner to get more dehumidification; that trade was the reason the old unit short-cycled. And we do not recommend a bigger portable unit, which dries one room, needs its bucket emptied daily and dumps its heat into the house. The whole-house unit drains to the condensate line and ducts its dry air to every room.

Ask about a whole-house dehumidifier

The day it goes in

One day, one crew from our Palm Coast headquarters. The unit hangs or sits beside the air handler in the garage, a return take-off and a supply connection are cut into the existing plenum, a dedicated drain with its own trap and float switch runs to the outdoor line, and a humidistat goes on the wall near the thermostat. We check the air handler’s drain and pan while we are in there, because in a house that has flooded, the pan is often where the mold started. Power comes from a new circuit at the panel. By mid-afternoon it is pulling water, and the couple watches the hygrometer drop through the evening.

Through the damp months

The unit runs most in May, June, September and October, the months when the house is damp without being hot, and on summer nights after rain. In July and August the air conditioner does most of the work and the dehumidifier tops it off. Owners typically raise the thermostat a degree or two because dry 76 feels better than damp 74, which claws back some of the dehumidifier’s running cost on the FPL bill. Maintenance is a filter rinse a few times a year and a drain check on the spring and fall visits.

The short word on humidifiers

The same house hits a different problem for about a week each January, when a front drops the overnight low into the 20s or 30s and the heat dries the air to the point of static and dry sinuses. For that week a portable bedroom humidifier is the honest answer. A whole-house humidifier in Ormond Beach would sit idle fifty weeks a year and add moisture to a house that spends the other fifty fighting it. We will install one if you insist, but we will say this first. Call 866-266-5709 and bring your hygrometer reading.