Dehumidifier to Stop Wall Condensation

Condensation forms where moist air meets a cooler wall

Condensation on an interior wall appears when room air holds more moisture than it can keep as vapor at the temperature of the wall surface. Warm, moist air contacts the cooler paint or plaster, and some of that moisture changes into visible droplets. That is a general description of condensation; a dehumidifier listing does not state how much condensation a room produces or how quickly it forms.

A dehumidifier removes moisture from the air that passes through it, so the room air holds less moisture. With less moisture in the air, there is less moisture available to condense on a cooler wall. This article explains how to read dehumidifier listings for that job; the site does not promise a drying rate, a humidity level a unit will reach, or a result for a specific wall.

Read the pints-per-day label as a stated figure

Dehumidifier listings state capacity in pints per day, which the ENERGY STAR program describes as the amount of water a unit can remove in 24 hours under stated conditions. The Department of Energy sets the measurement method for dehumidifiers, and the ENERGY STAR page on capacity ratings explains that the method changed over time. That is why a model can appear with two different pint figures: the maker states which rating method it used.

The pints-per-day figure is a label, not a measured result for your room. The site groups units by stated capacity tiers and compares listings on those stated details; see the main dehumidifier guide for how the tiers are ordered. For how area labels and capacity labels relate, see the capacity versus square footage article.

• Small: the site's small-unit guide, for listings with a lower stated pint figure.
• Mid: the 50 to 99 pint guide, for listings in that stated range.
• Large: the 100 pint and high-capacity guides, for listings with a higher stated figure.

Compressor or desiccant: the type words

Many listings name the type in the title or the first bullet: compressor, desiccant, or thermoelectric. A compressor unit condenses moisture on a refrigerated coil, and a desiccant unit uses a moisture-absorbing material. The type is a shopping label; the site does not measure how either type performs in a room.

For a cool room, the maker's page may state an operating temperature range. The ENERGY STAR dehumidifier page notes that frost can form on the coils when the air temperature drops below 65 degrees Fahrenheit and that some units include an anti-frost sensor. Read the stated range on the maker's page for the room where you plan to run the unit.

Drain options: bucket, hose, or pump

Listings describe how the unit collects condensate. A bucket is the removable water tank that fills and stops the unit when full. A continuous drain lets you connect a hose so the water runs out through a gravity drain, which needs the drain to be lower than the unit. A pump lifts condensate up to a drain that sits higher, which is why pump listings appear in basements without a floor drain.

A listing may say "pump included" or "drain hose included" as separate items. Read the drain section of the maker's manual for the fitting size and the hose routing, and see the drain options article and the pump benefits article for how these terms read on a listing.

Place the unit as the manual describes

A dehumidifier moves air through the unit and out again. For the air to move, the manual describes a level floor and clearance around the intake and the vents. Keep the front and the sides free so air can reach the unit; a unit pushed against a wall moves less air. See the placement tips article.

Condensation forms on the wall, not inside the unit, so the unit's job is to reduce the moisture in the room air over time. The listing does not state how long that takes. Run the unit according to the maker's instructions and read the manual for the controls.

The ENERGY STAR mark on a listing

A listing may carry the ENERGY STAR mark. ENERGY STAR is an EPA program that recognizes products that meet its efficiency criteria; the program's dehumidifier page states that certified models use more efficient refrigeration coils, compressors, and fans. The mark is a program label, and this site does not measure energy use or running cost.

If the mark matters to you, compare listings that carry it in the Energy Star guide, and check a model on the ENERGY STAR product finder. A listing without the mark is not a statement about efficiency on this site.

Wall condensation, moisture, and where to get help

Condensation is a moisture issue, and for guidance on mold and moisture in your home, read the mold pages from the EPA and the CDC, both listed in the sources below. This article does not restate or summarize that guidance.

If a wall stays damp or shows stains even with a unit running, the cause may be a leak, seepage, or a surface temperature issue rather than the air's moisture level. For anything about the structure of the home, contact a qualified contractor. Read the maker's manual for the unit's stated operating conditions.

What to pick for your situation

Questions

Will a dehumidifier stop condensation on a wall?

A dehumidifier removes moisture from the air, so the room air holds less moisture that can condense on a cooler wall. A listing does not state a drying rate for a specific room, and this site does not promise one. Read the stated capacity on the listing and the operating conditions on the maker's page.

What does pints per day mean on a dehumidifier listing?

The pints-per-day figure is the unit's stated capacity, which the ENERGY STAR program describes as the amount of water a unit can remove in 24 hours under stated conditions. The Department of Energy changed the rating method over time, which is why a model can show two different figures. The figure is a label, not a measured result for your room.

Why does one model list two pint figures?

The Department of Energy changed the rating method for portable dehumidifiers, and the ENERGY STAR page on capacity ratings explains that a unit rated under the newer method can report a smaller capacity than under the older one. Read the standard named on the maker's page next to the figure.

For a damp wall, is a pump or a drain hose better?

A drain hose works by gravity, so the drain has to be lower than the unit. A pump lifts condensate up to a higher drain, which is useful in a basement without a floor drain. Read the drain section of the maker's manual for the fitting, and compare pump and bucket listings on stated details.

Where should the unit go in a damp room?

Place the unit on a level floor and keep the intake and vents clear so air can move through it. The manual describes the clearance for the model. See the placement tips article for how placement reads as a shopping question.

What if a wall stays damp after the unit runs?

A damp wall can come from a leak or seepage, not just from moisture in the air. For anything about the structure of the home, contact a qualified contractor. Read the maker's manual for the unit's stated operating conditions.