Whole-House Dehumidifier

Rated at 70 to 155 pints per day, a Whole-House Dehumidifier is a ducted refrigerant machine that lives in a basement, a mechanical room or a sealed crawl space. It connects to the heating and cooling ducts or runs its own short duct to a grille, drains continuously to a floor drain or a condensate pump, and takes its orders from a wall mounted dehumidistat rather than a dial on the cabinet.

Two or three portable Refrigerant Dehumidifiers cost far less and each dries only the room it stands in, with buckets and trailing cords to match. Ducted equipment runs 1,500 to 3,500 dollars installed, treats a whole house at once and does it quietly, at 2.5 to 4.0 liters per kilowatt hour against 1.5 to 2.0 for a portable. Across a humid summer that efficiency gap repays part of the difference, though rarely the whole of it.

Sealed crawl spaces, large finished basements, humid climates where the air conditioner satisfies the thermostat while leaving the house at 60 percent, and homes with mechanical ventilation drawing in damp outdoor air are the cases that justify it. One damp room does not. Neither does a basement with water coming through the wall, since drying air forever is a worse answer than extending a downspout and correcting the grade outside.

Ask for pints per day at your conditions rather than the headline alone. Confirm the unit can run its own blower, because a machine depending on the furnace fan does nothing when heating and cooling are both idle. Check the filter rating, the drain arrangement and whether a pump is needed, and prefer a control with a few percent of dead band so it does not cycle every hour. Leave service clearance in a crawl space, since a coil you cannot reach never gets cleaned.

Installation needs a dedicated circuit, a trapped condensate drain falling at least a quarter inch per foot, and duct connections. An electrician and a heating contractor are both involved and a permit is often required. Rules vary by country, so check locally. Change the filter every three months, clean the coil annually and inspect the drain trap each spring. In a crawl space, keep the vapor barrier sealed and the vents closed, or the machine spends its life dehumidifying outdoor air.