A hygrometer reading 64 in Pleasant Street, and the equipment that answers it
The thermostat says the house is cool. The little humidity gauge on the bookshelf says otherwise. In Gainesville, the gauge is usually right.
The number on the bookshelf
A renter in the Pleasant Street Historic District bought a cheap hygrometer after noticing the bathroom door swelled shut every spring. On a May morning it reads 64 percent at 74 degrees. The window over the sink is fogged on the inside. A closet smells like a tent. The air conditioner is working fine; it simply has not needed to run much, because May in Gainesville is pleasant in temperature and already soggy in moisture.
That reading, and the same one from a slab ranch in East Gainesville and a Haile Plantation house with a new, efficient, oversized heat pump, is the case for a whole-house dehumidifier.
Who needs one here
Dehumidifiers earn their place in a specific set of Gainesville homes:
- Wood-frame historic houses in Duckpond, Pleasant Street and the Southeast district, whose envelopes breathe moisture in all day.
- Homes on crawlspaces or bare slabs without a vapor barrier, common in the 1960s and 1970s stock that makes up a large share of the city.
- Houses with new, high-efficiency cooling that reaches the setpoint quickly and shuts off before it has dried the air. Oversizing makes this worse.
- Rentals with mold complaints, where a landlord needs the humidity controlled whether or not the tenant touches the thermostat.
- Shaded homes under heavy canopy, where the roof never dries and the attic stays damp into the evening.
Humidifiers, by contrast, suit almost nobody in this climate for more than a few January weeks, and the aquifer’s hardness makes them a maintenance burden. We will say so rather than sell one.
How it works alongside the AC
An air conditioner removes moisture as a side effect of cooling: warm, wet air crosses a cold coil and water condenses out. When the house does not need cooling, no water comes out. A whole-house dehumidifier is a small refrigeration unit whose only job is that condensation. Ducted into the return side of the central system, it pulls air from the house, dries it, and returns it slightly warmer, running on its own humidistat whenever humidity rises above the setting regardless of what the thermostat wants. In a Gainesville spring and fall, when temperatures are mild and dew points are not, it is the only thing in the house doing the drying.
Sizing for local houses
Dehumidifiers are rated in pints per day. The number depends on the house’s volume, how leaky its envelope is, how many people and showers it holds, and whether it sits on a damp slab or over a crawlspace. A 1,400 square foot bungalow with original windows in the Southeast district can need more drying than a 2,400 square foot sealed house in the Town of Tioga. We measure rather than guess, and we check that the existing blower can take the small added return load. Where the dehumidifier goes depends on the house: a garage utility wall in Haile, a closet platform in a ranch, the attic beside the air handler in a historic home, with full overflow protection.
Running cost and incentives
A dehumidifier runs most in April, May, October and November, exactly when the AC runs least, so the two rarely stack on the same hour of the GRU bill. Most households recover some of its draw by living comfortably at a higher thermostat setting. There is no GRU or Clay Electric rebate specific to dehumidifiers that we are aware of; their programs center on heat pumps, duct testing and surveys, and we confirm current offerings for your address at the estimate. [[CONFIRM WITH JERRY]] The envelope fixes, sealing returns and adding a crawlspace vapor barrier, often cut the dehumidifier’s workload in half, and we will mention them before we size anything.
Humidity equipment questions from the historic districts
Why is my 1920s house damp in May when the AC barely runs?
Because the AC is the only thing drying it, and in May the outdoor temperature is mild enough that it rarely needs to. The dew point is already in the upper 60s, so moisture pours in through a wood-frame envelope faster than a short cooling cycle removes it. A dehumidifier works on humidity directly, regardless of temperature.
Will a whole-house dehumidifier raise my GRU bill?
It draws power, but most owners set the thermostat two or three degrees higher once the house is dry and the net change is small or favorable. A dry 78 feels better than a damp 74, and the AC runs less at 78.
Does anyone in Gainesville need a humidifier?
A few people, for a few weeks. During a January freeze stretch with the heat running, indoor humidity in a tight house can drop enough to bother skin and sinuses. Before recommending one we warn about the water: at around eight grains of hardness even after GRU’s softening, a humidifier scales fast and needs frequent cleaning.
Can the dehumidifier drain into the same line as the air handler?
Usually, with its own trap and a connection downstream of the air handler’s. In an attic install we add it to the secondary pan’s protection as well, so an overflow shuts the system off before it reaches a plaster ceiling.
House cool but clammy?
Call with your gauge reading and we'll tell you whether equipment or a repair is the answer.